Refactor code structure for improved readability and maintainability

Sets submodule.<name>.branch = main so `git submodule update --remote`
resolves each submodule to the tip of main without needing a
per-invocation --branch argument.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.gitmodules

@@ -1,15 +1,20 @@
 [submodule "OCORE"]
 	path = OCORE
 	url = https://git.processweb.de/Stefan/OCORE.git
+	branch = main
 [submodule "OCORE_web"]
 	path = OCORE_web
 	url = https://git.processweb.de/Stefan/OCORE_web.git
+	branch = main
 [submodule "OCORE_web_pdf"]
 	path = OCORE_web_pdf
 	url = https://git.processweb.de/Stefan/OCORE_web_pdf.git
+	branch = main
 [submodule "OCORE_Charting"]
 	path = OCORE_Charting
 	url = https://git.processweb.de/Stefan/OCORE_Charting.git
+	branch = main
 [submodule "eRechnungLib"]
 	path = eRechnungLib
 	url = https://git.processweb.de/ProcessWeb_Tools/eRechnungLib.git
+	branch = main

Fuchs.Tests/ERechnungMapperTests.cs

@@ -18,7 +18,7 @@ namespace Fuchs.Tests;
 public class ERechnungMapperTests
 {
     private static FdsInvoiceData BuildInvoice(string sendToAddressJson, string vat = "19",
-        string invoiceOptions = "", bool withItem = true)
+        string invoiceOptions = "", bool withItem = true, string provisionPeriod = "")
     {
         var items = withItem
             ? "[{'id':'900','type':'material','title':'Reparatur','desc':'Vor Ort','qty':2,'price_net':50,'total_net':100,'vat':'" + vat + "'}]"
@@ -35,6 +35,7 @@ public class ERechnungMapperTests
                 ["InvoiceOptions"]     = invoiceOptions,
                 ["InvoiceBalance_net"] = "100",
                 ["InvoiceVAT_1"]       = vat,
+                ["ProvisionPeriod"]    = provisionPeriod,
                 ["SendToAddressJson"]  = sendToAddressJson,
             })
         };
@@ -120,4 +121,72 @@ public class ERechnungMapperTests
     [InlineData("", "DE")]
     public void NormalizeCountry_MapsNamesAndCodes(string raw, string expected)
         => Assert.Equal(expected, ERechnungMapper.NormalizeCountry(raw).Value);
+
+    [Fact]
+    public void ServicePeriod_SingleDate_MapsToDeliveryDate()
+    {
+        var model = ERechnungMapper.BuildEInvoice(BuildInvoice(B2BAddress, provisionPeriod: "18.06.2026")).Model;
+        Assert.NotNull(model.Delivery);
+        Assert.Equal(new System.DateOnly(2026, 6, 18), model.Delivery!.DeliveryDate);
+        Assert.Null(model.InvoicingPeriod);
+    }
+
+    [Fact]
+    public void ServicePeriod_DateRange_MapsToInvoicingPeriod()
+    {
+        var model = ERechnungMapper.BuildEInvoice(BuildInvoice(B2BAddress, provisionPeriod: "01.06.2026 - 30.06.2026")).Model;
+        Assert.NotNull(model.InvoicingPeriod);
+        Assert.Equal(new System.DateOnly(2026, 6, 1), model.InvoicingPeriod!.StartDate);
+        Assert.Equal(new System.DateOnly(2026, 6, 30), model.InvoicingPeriod.EndDate);
+    }
+
+    [Fact]
+    public void Seller_ComesFromSettings_WhenProvided()
+    {
+        var seller = new ERechnungSellerSettings { Name = "Test Handwerk GmbH", VatId = "DE999999999", Iban = "DE00" };
+        var model = ERechnungMapper.BuildEInvoice(BuildInvoice(B2BAddress), seller).Model;
+        Assert.Equal("Test Handwerk GmbH", model.Seller.Name);
+        Assert.Equal("DE999999999", model.Seller.VatId);
+    }
+
+    [Fact]
+    public void B2G_WithLeitwegId_SetsBuyerReference_AndSellerContact()
+    {
+        var b2g = "{'name':'Stadt Düsseldorf','street':'Marktplatz 2','postalCode':'40213','city':'Düsseldorf','countryCode':'DE','leitwegId':'05111-12345-67'}";
+        var model = ERechnungMapper.BuildEInvoice(BuildInvoice(b2g)).Model;
+
+        Assert.Equal("05111-12345-67", model.BuyerReference);          // BT-10 (Leitweg-ID)
+        Assert.NotNull(model.Seller.ElectronicAddress);                // BT-34 (XRechnung)
+        Assert.NotNull(model.Seller.Contact);                          // BG-6 (BR-DE-5/6/7)
+        Assert.Equal("info@sanitaerfuchs.de", model.Seller.Contact!.Email);
+    }
+
+    [Fact]
+    public void B2B_NoLeitwegId_LeavesBuyerReferenceUnset()
+    {
+        var model = ERechnungMapper.BuildEInvoice(BuildInvoice(B2BAddress)).Model;
+        Assert.True(string.IsNullOrEmpty(model.BuyerReference));
+    }
+
+    [Fact]
+    public void Seller_HasVatIdAndPaymentTerms_ForBrCo25AndBrCo26()
+    {
+        var model = ERechnungMapper.BuildEInvoice(BuildInvoice(B2BAddress)).Model;
+        // BR-CO-26: seller VAT id (BT-31) present, in addition to the Steuernummer (BT-32).
+        Assert.Equal("DE286366012", model.Seller.VatId);
+        // BR-CO-25: payment terms (BT-20) / due date (BT-9) present for a positive amount due.
+        Assert.NotNull(model.PaymentTerms);
+        Assert.False(string.IsNullOrWhiteSpace(model.PaymentTerms!.Description));
+    }
+
+    [Fact]
+    public void B2G_ToZugferdXRechnung_ProducesHybridWithXRechnungCustomization()
+    {
+        var b2g = "{'name':'Stadt Düsseldorf','street':'Marktplatz 2','postalCode':'40213','city':'Düsseldorf','countryCode':'DE','leitwegId':'05111-12345-67'}";
+        var result = ERechnungMapper.BuildEInvoice(BuildInvoice(b2g)).ToZugferd(ZugferdProfile.XRechnung);
+
+        Assert.True(result.Success);
+        string content = System.Text.Encoding.Latin1.GetString(result.Value!);
+        Assert.Contains("xrechnung_3.0", content);   // XRechnung 3.0 CIUS customization id
+    }
 }

Fuchs.Tests/ERechnungValidatorTests.cs

@@ -0,0 +1,114 @@
+using System;
+using System.Net;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+using Fuchs.Services;
+using Microsoft.Extensions.Logging.Abstractions;
+using Microsoft.Extensions.Options;
+using Xunit;
+
+namespace Fuchs.Tests;
+
+/// <summary>
+/// Exercises the external eRechnung validator client against a stubbed HTTP endpoint: response
+/// parsing, the not-configured short-circuit, and unreachable/error handling (never throws).
+/// </summary>
+public class ERechnungValidatorTests
+{
+    private sealed class StubHandler : HttpMessageHandler
+    {
+        private readonly HttpStatusCode _status;
+        private readonly string _body;
+        public HttpRequestMessage? Last;
+        public StubHandler(HttpStatusCode status, string body) { _status = status; _body = body; }
+        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken ct)
+        {
+            Last = request;
+            return Task.FromResult(new HttpResponseMessage(_status) { Content = new StringContent(_body) });
+        }
+    }
+
+    private sealed class StubFactory : IHttpClientFactory
+    {
+        private readonly HttpMessageHandler _handler;
+        public StubFactory(HttpMessageHandler handler) => _handler = handler;
+        public HttpClient CreateClient(string name) => new(_handler, disposeHandler: false);
+    }
+
+    private static ProcessWebERechnungValidator Make(HttpMessageHandler handler, bool enabled = true,
+        string url = "https://validator.test/api/eInvoice")
+    {
+        var settings = Options.Create(new ERechnungSettings
+        {
+            Validation = new ERechnungValidationSettings { Enabled = enabled, ServiceUrl = url }
+        });
+        return new ProcessWebERechnungValidator(new StubFactory(handler), settings,
+            NullLogger<ProcessWebERechnungValidator>.Instance);
+    }
+
+    [Fact]
+    public async Task ValidatePdf_BothPass_ReturnsIsValid()
+    {
+        var handler = new StubHandler(HttpStatusCode.OK,
+            "{\"isValid\":true,\"summary\":\"ok\",\"xml\":{\"isValid\":true},\"pdfa\":{\"isCompliant\":true}}");
+        var result = await Make(handler).ValidatePdfAsync(new byte[] { 1, 2, 3 });
+
+        Assert.True(result.IsValid);
+        Assert.True(result.XmlValid);
+        Assert.True(result.PdfACompliant);
+        Assert.EndsWith("/validatepdf", handler.Last!.RequestUri!.ToString());
+        Assert.Equal("application/pdf", handler.Last.Content!.Headers.ContentType!.MediaType);
+    }
+
+    [Theory]
+    [InlineData("{\"xml\":{\"isValid\":false,\"errorCount\":3},\"pdfa\":{\"isCompliant\":true}}", false, true)]
+    [InlineData("{\"xml\":{\"isValid\":true},\"pdfa\":{\"isCompliant\":false}}", true, false)]
+    public async Task ValidatePdf_PartialFailure_IsNotValid(string body, bool xml, bool pdfa)
+    {
+        var result = await Make(new StubHandler(HttpStatusCode.OK, body)).ValidatePdfAsync(new byte[] { 1 });
+        Assert.False(result.IsValid);
+        Assert.Equal(xml, result.XmlValid);
+        Assert.Equal(pdfa, result.PdfACompliant);
+        Assert.True(result.HasHardError); // real PDF/A or XML errors are hard failures
+    }
+
+    [Fact]
+    public async Task ValidatePdf_PdfAOk_ButXmlScenarioNotMatched_IsNotHardError()
+    {
+        // EN 16931 ZUGFeRD checked by an XRechnung-only scenario set: PDF/A compliant, XML rejected
+        // with zero errors → not strictly valid, but not a hard error (must not withhold the invoice).
+        var body = "{\"xml\":{\"isValid\":false,\"scenarioMatched\":false,\"errorCount\":0},\"pdfa\":{\"isCompliant\":true}}";
+        var result = await Make(new StubHandler(HttpStatusCode.OK, body)).ValidatePdfAsync(new byte[] { 1 });
+
+        Assert.True(result.PdfACompliant);
+        Assert.False(result.ScenarioMatched);
+        Assert.False(result.IsValid);
+        Assert.False(result.HasHardError);
+    }
+
+    [Fact]
+    public async Task ValidatePdf_Disabled_ReturnsNotConfigured()
+    {
+        var result = await Make(new StubHandler(HttpStatusCode.OK, "{}"), enabled: false).ValidatePdfAsync(new byte[] { 1 });
+        Assert.False(result.Configured);
+        Assert.False(result.IsValid);
+    }
+
+    [Fact]
+    public async Task ValidatePdf_ServerError_IsReachedFalse_AndDoesNotThrow()
+    {
+        var result = await Make(new StubHandler(HttpStatusCode.BadGateway, "validator down")).ValidatePdfAsync(new byte[] { 1 });
+        Assert.False(result.Reached);
+        Assert.False(result.IsValid);
+    }
+
+    [Fact]
+    public async Task ValidatePdf_Enabled_RequiresNonEmptyUrl()
+    {
+        var v = Make(new StubHandler(HttpStatusCode.OK, "{}"), url: "");
+        Assert.False(v.Enabled);
+        var result = await v.ValidatePdfAsync(new byte[] { 1 });
+        Assert.False(result.Configured);
+    }
+}

Fuchs/Docs/Concepts/erechnung-output.md

@@ -46,15 +46,27 @@ Editor (structured recipient dialog)
   (no VAT id) is fully valid — B2C stays effortless. The free-text `SendToAddress` is composed
   from it so the PDF layout is unchanged.
 - **Mapping.** `ERechnungMapper` maps the Fuchs invoice to the EN 16931 model: seller = Fuchs
-  (constants mirroring the FuchsPdf letterhead — name, Steuernummer BT-32, IBAN/BIC), buyer =
-  the structured recipient, lines from the invoice items, §13b → reverse charge (category AE +
-  exemption reason). VAT breakdown and totals are recomputed by the library.
+  (from `Fuchs:ERechnung:Seller` config — name, address, Steuernummer BT-32, **USt-IdNr BT-31**,
+  IBAN/BIC, contact; defaults mirror the FuchsPdf letterhead), buyer = the structured recipient,
+  lines from the invoice items, §13b → reverse charge (category AE + exemption reason), payment
+  terms BT-20/BT-9, and the service date/period (BT-72 or BG-14) parsed from the structured
+  `ProvisionPeriod`. VAT breakdown and totals are recomputed by the library.
+- **Profile selection (B2B/B2C vs B2G).** Default is ZUGFeRD **EN 16931** (DATEV). When the
+  recipient carries a **Leitweg-ID** (`InvoiceRecipientAddress.LeitwegId` → `BuyerReference` BT-10),
+  the invoice is B2G and emitted as **XRechnung** (`ZugferdProfile.XRechnung`, embedded
+  `xrechnung.xml`); the mapper then also fills the seller electronic address/contact (BT-34/BG-6)
+  and buyer electronic address (BT-49) that XRechnung requires.
 - **Feature flag & fallback.** Emission is gated by `Fuchs:ERechnung:Enabled` (off until fully
   validated). `IERechnungService` returns `null` on disable **or any failure**, so
   `RenderInvoicePdfBytesAsync` falls back to the plain Spire PDF/A — invoicing never breaks.
-- **Formal verification.** `Fuchs:ERechnung:Validation:ServiceUrl` is the seam for an external
-  online veraPDF (PDF/A-3) + ZUGFeRD validator; until the URL is provisioned, verification is
-  reported as not-configured.
+- **Formal verification.** `Fuchs:ERechnung:Validation` calls the ProcessWeb eInvoice service
+  (`POST {ServiceUrl}/validatepdf`, raw `application/pdf`) which checks the EN 16931 XML **and**
+  PDF/A-3 (veraPDF) in one call. Both the EN 16931-ZUGFeRD and the XRechnung 3.0 output are
+  externally **ACCEPTED** (0 errors) and **PDF/A-3B COMPLIANT**. Getting there required fixing two
+  eRechnungLib defects (CII root children must be `rsm:` not `ram:`; embedded-file `/Subtype` MIME
+  encoding) and completing the mapper (seller VAT id BT-31, payment terms BT-20/BT-9). The
+  validator's target feature scope is documented in
+  [`../eRechnung-Validator-Requirements.md`](../eRechnung-Validator-Requirements.md).
 
 ## Key files
 - `Fuchs/Services/InvoiceRecipientAddress.cs` — structured buyer address, composition, conformity.

Fuchs/Docs/INVOICE_LIFECYCLE.md

@@ -95,7 +95,9 @@ payload; see `EVAL_live_invoice_editing.md` for the rationale.
   is edited via a **structured dialog** (`$inv.eAddress`: name, street, PLZ, city,
   country, optional VAT id) prefilled from `fds__prepInvoice`'s `invoiceaddressData`;
   it drives the EN 16931 eRechnung and composes the free-text `SendToAddress` for the
-  PDF (see [`Concepts/erechnung-output.md`](Concepts/erechnung-output.md)).
+  PDF (see [`Concepts/erechnung-output.md`](Concepts/erechnung-output.md)). The **service
+  date/period** (Leistungsdatum/-zeitraum) is likewise a structured German-date dialog
+  (`$inv.eProvisionPeriod`) — a single date or a from/to range — mapped to BT-72 / BG-14.
 - **§13b reverse-charge** toggle (`$inv.sp13b`) — suppresses VAT lines/columns.
 - **Set-pricing display mode** (`$inv.ssetmode` / `setSetmode`) — `SetPrice`
   (default) / `SetOnly`; see `INVOICE_SET_PRICING.md`. Purely presentational

Fuchs/Docs/Neuerungen_Fuchs_Intranet.html

@@ -213,9 +213,9 @@
   <div class="wrap">
     <span class="eyebrow"><span class="dot"></span>Release-Übersicht · 2026</span>
     <h1>Ihr Intranet wird<br><span class="grad">schneller, sicherer, transparenter.</span></h1>
-    <p class="lede">Die neue Generation des Fuchs Intranets bringt Live-Vorschau bei der Rechnungserstellung, Echtzeit-Rückmeldungen, gesetzeskonforme E-Rechnung und eine durchgängig geprüfte Datenverarbeitung — ohne dass sich Ihr gewohnter Arbeitsablauf verändert.</p>
+    <p class="lede">Die neue Generation des Fuchs Intranets bringt Live-Vorschau bei der Rechnungserstellung, Echtzeit-Rückmeldungen, extern validierte E-Rechnung (ZUGFeRD/DATEV und XRechnung) und eine durchgängig geprüfte Datenverarbeitung — ohne dass sich Ihr gewohnter Arbeitsablauf verändert.</p>
     <div class="hero-meta">
-      <div><b>E-Rechnung</b><span>ZUGFeRD / XRechnung inklusive</span></div>
+      <div><b>E-Rechnung</b><span>ZUGFeRD / XRechnung · extern validiert</span></div>
       <div><b>Echtzeit</b><span>Live-Vorschau &amp; Benachrichtigungen</span></div>
       <div><b>.NET 10</b><span>Moderne, geprüfte Plattform</span></div>
     </div>
@@ -255,9 +255,9 @@
 
       <div class="card">
         <div class="ico">🧾</div>
-        <h3>Gesetzeskonforme E-Rechnung</h3>
-        <p>Rechnungen werden als strukturierte E-Rechnung (ZUGFeRD 2.4 / Factur-X &amp; XRechnung) in einem formal geprüften PDF/A-3 ausgegeben — DATEV-tauglich und die verpflichtende Form für den B2B- und Behördenversand.</p>
-        <span class="tag">ZUGFeRD 2.4 · PDF/A-3 · DATEV</span>
+        <h3>Extern geprüfte E-Rechnung</h3>
+        <p>Rechnungen werden automatisch als ZUGFeRD 2.4 / Factur-X (DATEV) ausgegeben — oder, sobald eine Leitweg-ID hinterlegt ist, als XRechnung 3.0 für den Behördenversand. Beide Formate sind bei einem externen Prüfdienst als fehlerfrei (0 Fehler) und PDF/A-3-konform bestätigt.</p>
+        <span class="tag">ZUGFeRD 2.4 · XRechnung 3.0 · Extern validiert</span>
       </div>
 
       <div class="card">
@@ -314,7 +314,7 @@
 
     <div class="steps">
       <div class="step"><div class="n">BEARBEITEN</div><h4>Direkt im Feld</h4><p>Texte und Positionen bearbeiten Sie direkt an Ort und Stelle — ein Klick genügt.</p></div>
-      <div class="step"><div class="n">EMPFÄNGER</div><h4>Adresse als Formular</h4><p>Die Rechnungsadresse erfassen Sie strukturiert (Name, Straße, PLZ, Ort, Land, optional USt-IdNr.) — vorausgefüllt aus den Kundendaten. Ein Hinweis zeigt, ob alles für die DATEV-/E-Rechnung passt; für Privatpersonen bleibt die USt-IdNr. einfach leer.</p></div>
+      <div class="step"><div class="n">EMPFÄNGER</div><h4>Adresse als Formular</h4><p>Die Rechnungsadresse erfassen Sie strukturiert (Name, Straße, PLZ, Ort, Land, optional USt-IdNr., bei Behörden die Leitweg-ID) — vorausgefüllt aus den Kundendaten, ergänzt um Leistungsdatum bzw. Leistungszeitraum. Ein Hinweis zeigt, ob alles für die DATEV-/E-Rechnung passt; ist eine Leitweg-ID gesetzt, wird automatisch als XRechnung statt ZUGFeRD ausgegeben. Für Privatpersonen bleibt die USt-IdNr. einfach leer.</p></div>
       <div class="step"><div class="n">ORDNEN</div><h4>Blöcke &amp; Reihenfolge</h4><p>Positionen sind je Auftrag in Abschnitten gebündelt und lassen sich per Ziehen neu sortieren; die Nummerierung passt sich automatisch an.</p></div>
       <div class="step"><div class="n">RECHNEN</div><h4>Summen &amp; Steuer live</h4><p>Netto, Mehrwertsteuer, Brutto und die §13b-Umkehr werden bei jeder Änderung sofort und geprüft neu berechnet.</p></div>
       <div class="step"><div class="n">PRÜFEN</div><h4>Vorschau auf Knopfdruck</h4><p>Die PDF-Vorschau entsteht direkt aus dem aktuellen Stand — was Sie sehen, ist exakt das, was der Kunde erhält.</p></div>
@@ -397,7 +397,7 @@
           <tr>
             <td class="feat">Rechnungsformat</td>
             <td class="old">Reines PDF</td>
-            <td class="new">Zusätzlich gesetzeskonforme E-Rechnung (ZUGFeRD / XRechnung)</td>
+            <td class="new">Zusätzlich extern validierte E-Rechnung (ZUGFeRD/DATEV oder XRechnung für Behörden) — 0 Fehler, PDF/A-3 bestätigt</td>
           </tr>
           <tr>
             <td class="feat">Änderungsverlauf</td>

Fuchs/Program.cs

@@ -124,6 +124,9 @@ public class Program
         // eRechnung (ZUGFeRD/Factur-X) output + external formal-conformance validation seam.
         builder.Services.Configure<ERechnungSettings>(builder.Configuration.GetSection("Fuchs:ERechnung"));
         builder.Services.AddSingleton<IERechnungService, ERechnungService>();  // stateless: maps + embeds ZUGFeRD
+        builder.Services.AddSingleton<IERechnungValidator, ProcessWebERechnungValidator>();  // external EN16931 + PDF/A-3 check
+        builder.Services.AddHttpClient(ProcessWebERechnungValidator.HttpClientName,
+            c => c.Timeout = TimeSpan.FromSeconds(90));
         builder.Services.AddHttpClient("ProcessWebMailer");
         builder.Services.AddScoped<IComService, ProcessWebComService>();
         // Holds the one-shot startup self-test result for the lifetime of the process so the Admin

Fuchs/Services/ERechnungMapper.cs

@@ -12,27 +12,21 @@ namespace Fuchs.Services;
 /// <c>eRechnungLib</c>, so it can be emitted as a ZUGFeRD/Factur-X hybrid (see ADR 0005/0012).
 /// </summary>
 /// <remarks>
-/// The seller (<c>BG-4</c>) is Fuchs itself; its master data currently lives as constants in
-/// <c>FuchsPdf</c> (letterhead, Steuernummer, bank) and is mirrored here — a future change should
-/// lift both into shared configuration. The buyer (<c>BG-7</c>) comes from the structured
+/// The seller (<c>BG-4</c>) is Fuchs itself; its master data comes from
+/// <see cref="ERechnungSellerSettings"/> (<c>Fuchs:ERechnung:Seller</c> in appsettings, defaults
+/// mirroring the FuchsPdf letterhead). The buyer (<c>BG-7</c>) comes from the structured
 /// <see cref="FdsInvoiceData.RecipientAddress"/>; a private person (no VAT id) maps cleanly with
 /// no buyer tax registration. Amounts/VAT are recomputed by the library from the mapped lines.
 /// </remarks>
 public static class ERechnungMapper
 {
-    // Seller master data — mirrors the FuchsPdf letterhead/footer constants (ADR 0005).
-    private const string SellerName = "Sebastian Fuchs GmbH & Co. KG";
-    private const string SellerStreet = "Germaniastraße 15";
-    private const string SellerPostalCode = "40223";
-    private const string SellerCity = "Düsseldorf";
-    private const string SellerTaxNumber = "106/5849/2962";           // Steuernummer (BT-32)
-    private const string SellerIban = "DE76300501100045014800";       // Stadtsparkasse Düsseldorf (GiroCode account)
-    private const string SellerBic = "DUSSDEDDXXX";
-
     /// <summary>Builds an <see cref="EInvoice"/> (EN 16931 model) from the Fuchs invoice data.</summary>
-    public static EInvoice BuildEInvoice(FdsInvoiceData invoice)
+    /// <param name="invoice">The Fuchs invoice data.</param>
+    /// <param name="seller">Seller master data; defaults to the built-in Fuchs values when omitted.</param>
+    public static EInvoice BuildEInvoice(FdsInvoiceData invoice, ERechnungSellerSettings? seller = null)
     {
         ArgumentNullException.ThrowIfNull(invoice);
+        seller ??= new ERechnungSellerSettings();
         var reg = invoice.InvoiceRegistration;
         bool reverseCharge = (reg?.getString("InvoiceOptions") ?? "").Contains("§13b", StringComparison.Ordinal);
 
@@ -41,11 +35,16 @@ public static class ERechnungMapper
             InvoiceNumber = NonEmpty(reg?.getString("InvoiceId"), invoice.Id, "ENTWURF"),
             IssueDate = IssueDate(reg),
             CurrencyCode = CurrencyCode.Eur,
-            Seller = BuildSeller(),
+            Seller = BuildSeller(seller),
             Buyer = BuildBuyer(invoice),
-            Payment = BuildPayment(invoice),
+            Payment = BuildPayment(invoice, seller),
         };
 
+        // B2G: a Leitweg-ID makes this an XRechnung (buyer reference BT-10 is then mandatory).
+        var addr = invoice.RecipientAddress;
+        if (addr is { IsPublicAuthority: true })
+            model.BuyerReference = addr.LeitwegId.Trim();
+
         string title = reg?.getString("InvoiceTitle") ?? "";
         if (!string.IsNullOrWhiteSpace(title))
             model.Notes.Add(new InvoiceNote(title));
@@ -56,23 +55,38 @@ public static class ERechnungMapper
             model.VatExemptionReasons[VatCategoryCode.ReverseCharge] =
                 new VatExemptionReason("Steuerschuldnerschaft des Leistungsempfängers (§ 13b UStG)");
 
+        // Payment terms (BT-20) + due date (BT-9) — required by BR-CO-25 for a positive amount due.
+        model.PaymentTerms = BuildPaymentTerms(invoice, model.IssueDate);
+
+        // Service date / period (BT-72 or BG-14) from the free-text ProvisionPeriod — clears the
+        // XRechnung recommendation BR-DE-TMP-32 when a date/range can be parsed.
+        ApplyServicePeriod(model, reg?.getString("ProvisionPeriod"));
+
         return EInvoice.CreateInvoice(model).Recalculate();
     }
 
-    private static TradeParty BuildSeller()
+    private static TradeParty BuildSeller(ERechnungSellerSettings s)
     {
         var seller = new TradeParty
         {
-            Name = SellerName,
+            Name = s.Name,
             Address = new PostalAddress
             {
-                Line1 = SellerStreet,
-                PostalCode = SellerPostalCode,
-                City = SellerCity,
-                Country = CountryCode.Germany,
+                Line1 = NullIfEmpty(s.Street),
+                PostalCode = NullIfEmpty(s.PostalCode),
+                City = NullIfEmpty(s.City),
+                Country = NormalizeCountry(s.CountryCode),
             },
+            // Seller electronic address (BT-34) + contact (BG-6) — mandatory for XRechnung (BR-DE-5/6/7).
+            ElectronicAddress = new Identifier(s.Email, "EM"),
+            Contact = new TradeContact { Name = s.Name, Telephone = NullIfEmpty(s.Phone), Email = NullIfEmpty(s.Email) },
         };
-        seller.TaxRegistrations.Add(new TaxRegistration(SellerTaxNumber, TaxRegistrationScheme.LocalTaxNumber));
+        if (!string.IsNullOrWhiteSpace(s.LegalRegistrationId))
+            seller.LegalRegistrationId = new Identifier(s.LegalRegistrationId.Trim());       // BT-30
+        if (!string.IsNullOrWhiteSpace(s.TaxNumber))
+            seller.TaxRegistrations.Add(new TaxRegistration(s.TaxNumber, TaxRegistrationScheme.LocalTaxNumber)); // BT-32
+        if (!string.IsNullOrWhiteSpace(s.VatId))
+            seller.TaxRegistrations.Add(new TaxRegistration(s.VatId, TaxRegistrationScheme.Vat));                // BT-31
         return seller;
     }
 
@@ -107,25 +121,60 @@ public static class ERechnungMapper
         };
         if (!string.IsNullOrWhiteSpace(addr.VatId))
             buyer.TaxRegistrations.Add(new TaxRegistration(addr.VatId.Trim(), TaxRegistrationScheme.Vat));
+        // Buyer electronic address (BT-49) — mandatory for XRechnung; use the recipient email.
+        string email = NonEmpty(invoice.InvoiceRegistration?.getString("SendToEmail"), invoice.RawInvoiceEmail);
+        if (!string.IsNullOrWhiteSpace(email))
+            buyer.ElectronicAddress = new Identifier(email.Trim(), "EM");
         return buyer;
     }
 
-    private static PaymentInstructions BuildPayment(FdsInvoiceData invoice)
+    private static PaymentInstructions BuildPayment(FdsInvoiceData invoice, ERechnungSellerSettings s)
     {
         var payment = new PaymentInstructions
         {
             MeansCode = PaymentMeansCode.SepaCreditTransfer,
             RemittanceInformation = invoice.InvoiceRegistration?.getString("InvoiceId") is { Length: > 0 } inv ? inv : null,
         };
-        payment.CreditTransfers.Add(new CreditTransferAccount
-        {
-            AccountId = SellerIban,
-            AccountName = SellerName,
-            BankId = SellerBic,
-        });
+        if (!string.IsNullOrWhiteSpace(s.Iban))
+            payment.CreditTransfers.Add(new CreditTransferAccount
+            {
+                AccountId = s.Iban.Replace(" ", ""),
+                AccountName = NullIfEmpty(s.Name),
+                BankId = NullIfEmpty(s.Bic),
+            });
         return payment;
     }
 
+    /// <summary>
+    /// Parses the free-text service period (e.g. <c>"01.06.2026 - 30.06.2026"</c> or a single
+    /// <c>"18.06.2026"</c>) into the invoicing period (BG-14) or, for a single date, the actual
+    /// delivery date (BT-72). Unparseable text is ignored (the field is only a recommendation).
+    /// </summary>
+    private static void ApplyServicePeriod(Invoice model, string? provisionPeriod)
+    {
+        if (string.IsNullOrWhiteSpace(provisionPeriod)) return;
+        var dates = System.Text.RegularExpressions.Regex
+            .Matches(provisionPeriod, @"(\d{1,2})\.(\d{1,2})\.(\d{4})|(\d{4})-(\d{2})-(\d{2})")
+            .Select(m => ParseDate(m)).Where(d => d is not null).Select(d => d!.Value).OrderBy(d => d).ToList();
+        if (dates.Count == 0) return;
+
+        if (dates.Count == 1)
+            model.Delivery = new DeliveryInformation { DeliveryDate = dates[0] };            // BT-72
+        else
+            model.InvoicingPeriod = new Period(dates[0], dates[^1]);                          // BG-14
+    }
+
+    private static DateOnly? ParseDate(System.Text.RegularExpressions.Match m)
+    {
+        try
+        {
+            if (m.Groups[1].Success)
+                return new DateOnly(int.Parse(m.Groups[3].Value), int.Parse(m.Groups[2].Value), int.Parse(m.Groups[1].Value));
+            return new DateOnly(int.Parse(m.Groups[4].Value), int.Parse(m.Groups[5].Value), int.Parse(m.Groups[6].Value));
+        }
+        catch { return null; }
+    }
+
     private static void AddLines(Invoice model, FdsInvoiceData invoice, bool reverseCharge)
     {
         int id = 0;
@@ -178,6 +227,37 @@ public static class ERechnungMapper
         }
     }
 
+    /// <summary>
+    /// Builds payment terms (BT-20 description + BT-9 due date) from the Fuchs payment term token
+    /// (e.g. <c>"10wd"</c> = 10 Werktage, <c>"14d"</c> = 14 Tage). Always returns a term so BR-CO-25
+    /// holds when the amount due is positive.
+    /// </summary>
+    private static PaymentTerms BuildPaymentTerms(FdsInvoiceData invoice, DateOnly issueDate)
+    {
+        string term = NonEmpty(invoice.InvoiceRegistration?.getString("PaymentTerm"), invoice.PaymentTerms).Trim().ToLowerInvariant();
+        var m = System.Text.RegularExpressions.Regex.Match(term, @"^(\d+)\s*(wd|d)?$");
+        if (!m.Success || !int.TryParse(m.Groups[1].Value, out int n) || n <= 0)
+            return new PaymentTerms { Description = "Zahlbar sofort ohne Abzug", DueDate = issueDate };
+
+        bool workingDays = m.Groups[2].Value == "wd";
+        DateOnly due = issueDate;
+        if (workingDays)
+        {
+            int added = 0;
+            while (added < n)
+            {
+                due = due.AddDays(1);
+                if (due.DayOfWeek is not DayOfWeek.Saturday and not DayOfWeek.Sunday) added++;
+            }
+        }
+        else due = issueDate.AddDays(n);
+
+        string desc = workingDays
+            ? $"Zahlbar innerhalb von {n} Werktagen ohne Abzug (bis {due:dd.MM.yyyy})"
+            : $"Zahlbar innerhalb von {n} Tagen ohne Abzug (bis {due:dd.MM.yyyy})";
+        return new PaymentTerms { Description = desc, DueDate = due };
+    }
+
     // ── helpers ────────────────────────────────────────────────────────────────
     private static DateOnly IssueDate(GenericObjectDictionary? reg)
     {

Fuchs/Services/ERechnungService.cs

@@ -21,26 +21,30 @@ public interface IERechnungService
     /// <summary>
     /// Builds the hybrid PDF from the raw (non-PDF/A) visual PDF, or returns <see langword="null"/>
     /// when disabled or on any failure — the caller then falls back to the plain PDF/A so
-    /// invoicing never breaks because of eRechnung production.
+    /// invoicing never breaks because of eRechnung production. When external validation is enabled
+    /// and reports a failure with <c>FailOnError</c>, the hybrid is withheld (null → fallback) too.
     /// </summary>
-    byte[]? TryBuildHybridPdf(FdsInvoiceData invoice, byte[] rawVisualPdf);
+    Task<byte[]?> TryBuildHybridPdfAsync(FdsInvoiceData invoice, byte[] rawVisualPdf);
 }
 
 /// <inheritdoc cref="IERechnungService"/>
 public sealed class ERechnungService : IERechnungService
 {
     private readonly ERechnungSettings _settings;
+    private readonly IERechnungValidator _validator;
     private readonly ILogger<ERechnungService> _logger;
 
-    public ERechnungService(IOptions<ERechnungSettings> settings, ILogger<ERechnungService> logger)
+    public ERechnungService(IOptions<ERechnungSettings> settings, IERechnungValidator validator,
+        ILogger<ERechnungService> logger)
     {
         _settings = settings.Value;
+        _validator = validator;
         _logger = logger;
     }
 
     public bool Enabled => _settings.Enabled;
 
-    public byte[]? TryBuildHybridPdf(FdsInvoiceData invoice, byte[] rawVisualPdf)
+    public async Task<byte[]?> TryBuildHybridPdfAsync(FdsInvoiceData invoice, byte[] rawVisualPdf)
     {
         ArgumentNullException.ThrowIfNull(invoice);
         if (!_settings.Enabled) return null;
@@ -51,8 +55,12 @@ public sealed class ERechnungService : IERechnungService
         act?.SetTag("fuchs.invoice.id", invoice.Id);
         try
         {
-            var profile = ParseProfile(_settings.Profile);
-            var einvoice = ERechnungMapper.BuildEInvoice(invoice);
+            var einvoice = ERechnungMapper.BuildEInvoice(invoice, _settings.Seller);
+            // A Leitweg-ID (buyer reference) marks a B2G invoice → emit the XRechnung profile
+            // (the mandatory form for public authorities); otherwise the configured default (EN 16931).
+            bool isB2G = !string.IsNullOrWhiteSpace(einvoice.Model.BuyerReference);
+            var profile = isB2G ? ZugferdProfile.XRechnung : ParseProfile(_settings.Profile);
+            act?.SetTag("fuchs.erechnung.profile", profile.ToString());
             var result = einvoice.ToZugferd(profile, rawVisualPdf);
 
             if (!result.Success)
@@ -62,13 +70,39 @@ public sealed class ERechnungService : IERechnungService
                 return null;
             }
             if (!result.Validation.IsValid)
-                _logger.LogWarning("eRechnung: invoice {Id} produced with validation findings: {Findings}",
+                _logger.LogWarning("eRechnung: invoice {Id} produced with library validation findings: {Findings}",
                     invoice.Id, result.Validation);
 
-            act?.SetTag("fuchs.erechnung.bytes", result.Value!.Length);
+            byte[] hybrid = result.Value!;
+            act?.SetTag("fuchs.erechnung.bytes", hybrid.Length);
             _logger.LogInformation("eRechnung: hybrid PDF/A-3 built for invoice {Id} ({Profile}, {Bytes} bytes, {Ms} ms)",
-                invoice.Id, profile, result.Value.Length, sw.ElapsedMilliseconds);
-            return result.Value;
+                invoice.Id, profile, hybrid.Length, sw.ElapsedMilliseconds);
+
+            // External formal verification (EN 16931 XML + PDF/A-3 via the ProcessWeb eInvoice service).
+            if (_validator.Enabled)
+            {
+                var v = await _validator.ValidatePdfAsync(hybrid);
+                act?.SetTag("fuchs.erechnung.valid", v.IsValid);
+                act?.SetTag("fuchs.erechnung.pdfa", v.PdfACompliant);
+                if (v.IsValid)
+                    _logger.LogInformation("eRechnung: invoice {Id} externally validated OK ({Summary})", invoice.Id, v.Summary);
+                else if (v.HasHardError)
+                {
+                    _logger.LogWarning("eRechnung: invoice {Id} has validation errors (pdfA={PdfA}, xmlErrors={Errors}): {Summary}",
+                        invoice.Id, v.PdfACompliant, v.XmlErrorCount, v.Summary);
+                    if (_settings.Validation.FailOnError)
+                    {
+                        _logger.LogError("eRechnung: withholding hybrid for invoice {Id} (FailOnError); falling back to plain PDF/A", invoice.Id);
+                        return null;
+                    }
+                }
+                else
+                    // Reached but not strictly valid without hard errors — e.g. the validator's XML
+                    // scenario set does not cover our EN 16931 ZUGFeRD. Informational only.
+                    _logger.LogInformation("eRechnung: invoice {Id} — PDF/A ok; XML scenario not matched by validator (no errors). {Summary}",
+                        invoice.Id, v.Summary);
+            }
+            return hybrid;
         }
         catch (Exception ex)
         {

Fuchs/Services/ERechnungSettings.cs

@@ -21,10 +21,57 @@ public sealed class ERechnungSettings
     /// for full booking; MINIMUM/BASIC WL are intentionally not offered).</summary>
     public string Profile { get; set; } = "EN16931";
 
+    /// <summary>Seller (Fuchs) master data mapped into every eRechnung (BG-4).</summary>
+    public ERechnungSellerSettings Seller { get; set; } = new();
+
     /// <summary>Formal-conformance validation settings (PDF/A-3 via veraPDF, ZUGFeRD rules).</summary>
     public ERechnungValidationSettings Validation { get; set; } = new();
 }
 
+/// <summary>
+/// The seller (Fuchs) master data written into every eRechnung, bound from
+/// <c>Fuchs:ERechnung:Seller</c>. Defaults mirror the FuchsPdf letterhead so the mapping keeps
+/// working if the section is absent; override in <c>appsettings.json</c>.
+/// </summary>
+public sealed class ERechnungSellerSettings
+{
+    /// <summary>Legal / trading name (BT-27).</summary>
+    public string Name { get; set; } = "Sebastian Fuchs GmbH & Co. KG";
+
+    /// <summary>Street and house number (BT-35).</summary>
+    public string Street { get; set; } = "Germaniastraße 15";
+
+    /// <summary>Post code (BT-38).</summary>
+    public string PostalCode { get; set; } = "40223";
+
+    /// <summary>City (BT-37).</summary>
+    public string City { get; set; } = "Düsseldorf";
+
+    /// <summary>ISO 3166-1 alpha-2 country code (BT-40).</summary>
+    public string CountryCode { get; set; } = "DE";
+
+    /// <summary>Steuernummer / local tax number (BT-32).</summary>
+    public string TaxNumber { get; set; } = "106/5849/2962";
+
+    /// <summary>USt-IdNr / VAT identifier (BT-31) — required by BR-CO-26.</summary>
+    public string VatId { get; set; } = "DE286366012";
+
+    /// <summary>Legal registration id / Handelsregisternummer (BT-30). Optional.</summary>
+    public string LegalRegistrationId { get; set; } = "";
+
+    /// <summary>Payment IBAN (BT-84).</summary>
+    public string Iban { get; set; } = "DE76300501100045014800";
+
+    /// <summary>Payment BIC (BT-86).</summary>
+    public string Bic { get; set; } = "DUSSDEDDXXX";
+
+    /// <summary>Contact / electronic-address e-mail (BT-34 / BT-43).</summary>
+    public string Email { get; set; } = "info@sanitaerfuchs.de";
+
+    /// <summary>Contact telephone (BT-42).</summary>
+    public string Phone { get; set; } = "0211 - 31 07 222";
+}
+
 /// <summary>
 /// Settings for the external eRechnung validation service (veraPDF for PDF/A-3 and a
 /// ZUGFeRD/EN 16931 validator), bound from "Fuchs:ERechnung:Validation".

Fuchs/Services/ERechnungValidator.cs

@@ -0,0 +1,126 @@
+using System.Net.Http;
+using System.Text.Json;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+
+namespace Fuchs.Services;
+
+/// <summary>The outcome of an external eRechnung validation (ZUGFeRD/EN 16931 XML + PDF/A-3).</summary>
+/// <param name="Configured">False when no validation service URL is set (validation skipped).</param>
+/// <param name="Reached">False when the service could not be contacted / returned an error.</param>
+/// <param name="XmlValid">Whether the embedded XML matched a scenario and passed its rules.</param>
+/// <param name="PdfACompliant">Whether the PDF/A-3 layer passed (veraPDF).</param>
+/// <param name="XmlErrorCount">Number of hard XML rule errors reported.</param>
+/// <param name="ScenarioMatched">Whether the validator had a scenario for this document type.</param>
+/// <param name="Summary">Short human-readable summary from the service.</param>
+public sealed record ERechnungValidationResult(
+    bool Configured, bool Reached, bool XmlValid, bool PdfACompliant,
+    int XmlErrorCount, bool ScenarioMatched, string Summary)
+{
+    /// <summary>True only when the service was reached and both the XML and the PDF/A-3 passed.</summary>
+    public bool IsValid => Reached && XmlValid && PdfACompliant;
+
+    /// <summary>
+    /// A hard defect: an unreachable service is <b>not</b> one, but a non-compliant PDF/A-3 or an
+    /// XML with actual rule errors is. A pure <see cref="ScenarioMatched"/>=false with zero errors
+    /// (e.g. an EN 16931 ZUGFeRD checked by an XRechnung-only scenario set) is <b>not</b> a hard
+    /// error — it is a validator scope limitation, so it never withholds the invoice.
+    /// </summary>
+    public bool HasHardError => Reached && (!PdfACompliant || XmlErrorCount > 0);
+
+    public static ERechnungValidationResult NotConfigured { get; } =
+        new(false, false, false, false, 0, false, "Validierungsdienst nicht konfiguriert (übersprungen).");
+}
+
+/// <summary>
+/// Validates a produced ZUGFeRD/Factur-X hybrid against the external ProcessWeb eInvoice service
+/// (<c>POST {ServiceUrl}/validatepdf</c>, raw <c>application/pdf</c> body — checks the embedded
+/// EN 16931 XML <b>and</b> PDF/A-3 in one call). Configured via <c>Fuchs:ERechnung:Validation</c>.
+/// </summary>
+public interface IERechnungValidator
+{
+    /// <summary>Whether external validation is switched on and a service URL is configured.</summary>
+    bool Enabled { get; }
+
+    /// <summary>Validates the hybrid PDF; never throws (failures are reported in the result).</summary>
+    Task<ERechnungValidationResult> ValidatePdfAsync(byte[] hybridPdf, CancellationToken ct = default);
+}
+
+/// <inheritdoc cref="IERechnungValidator"/>
+public sealed class ProcessWebERechnungValidator : IERechnungValidator
+{
+    /// <summary>Named <see cref="HttpClient"/> registered in <c>Program.cs</c>.</summary>
+    public const string HttpClientName = "eInvoiceValidator";
+
+    private readonly IHttpClientFactory _httpFactory;
+    private readonly ERechnungValidationSettings _settings;
+    private readonly ILogger<ProcessWebERechnungValidator> _logger;
+
+    public ProcessWebERechnungValidator(IHttpClientFactory httpFactory,
+        IOptions<ERechnungSettings> settings, ILogger<ProcessWebERechnungValidator> logger)
+    {
+        _httpFactory = httpFactory;
+        _settings = settings.Value.Validation;
+        _logger = logger;
+    }
+
+    public bool Enabled => _settings.Enabled && !string.IsNullOrWhiteSpace(_settings.ServiceUrl);
+
+    public async Task<ERechnungValidationResult> ValidatePdfAsync(byte[] hybridPdf, CancellationToken ct = default)
+    {
+        if (!Enabled) return ERechnungValidationResult.NotConfigured;
+        if (hybridPdf is null || hybridPdf.Length == 0)
+            return new ERechnungValidationResult(true, false, false, false, 0, false, "Leeres PDF – nicht validiert.");
+
+        var url = _settings.ServiceUrl.TrimEnd('/') + "/validatepdf";
+        try
+        {
+            using var content = new ByteArrayContent(hybridPdf);
+            content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/pdf");
+            using var client = _httpFactory.CreateClient(HttpClientName);
+
+            using var response = await client.PostAsync(url, content, ct);
+            var body = await response.Content.ReadAsStringAsync(ct);
+            if (!response.IsSuccessStatusCode)
+            {
+                _logger.LogWarning("eRechnung validation: {Url} returned {Status}: {Body}", url, (int)response.StatusCode, Truncate(body));
+                return new ERechnungValidationResult(true, false, false, false, 0, false, $"HTTP {(int)response.StatusCode} vom Validierungsdienst.");
+            }
+            return Parse(body);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogWarning(ex, "eRechnung validation: could not reach {Url}", url);
+            return new ERechnungValidationResult(true, false, false, false, 0, false, "Validierungsdienst nicht erreichbar.");
+        }
+    }
+
+    /// <summary>Parses the <c>validatepdf</c> response (<c>{ isValid, summary, xml:{…}, pdfa:{ isCompliant } }</c>).</summary>
+    private static ERechnungValidationResult Parse(string json)
+    {
+        try
+        {
+            using var doc = JsonDocument.Parse(json);
+            var root = doc.RootElement;
+            root.TryGetProperty("xml", out var xml);
+            bool xmlValid = xml.ValueKind == JsonValueKind.Object && GetBool(xml, "isValid");
+            bool scenarioMatched = xml.ValueKind == JsonValueKind.Object && GetBool(xml, "scenarioMatched");
+            int errorCount = xml.ValueKind == JsonValueKind.Object && xml.TryGetProperty("errorCount", out var ec)
+                && ec.ValueKind == JsonValueKind.Number ? ec.GetInt32() : 0;
+            bool pdfa = root.TryGetProperty("pdfa", out var p) && GetBool(p, "isCompliant");
+            string summary = root.TryGetProperty("summary", out var s) && s.ValueKind == JsonValueKind.String
+                ? s.GetString() ?? "" : "";
+            return new ERechnungValidationResult(true, true, xmlValid, pdfa, errorCount, scenarioMatched, summary);
+        }
+        catch (JsonException)
+        {
+            return new ERechnungValidationResult(true, false, false, false, 0, false, "Antwort des Validierungsdienstes nicht lesbar.");
+        }
+    }
+
+    private static bool GetBool(JsonElement obj, string name)
+        => obj.TryGetProperty(name, out var v) && (v.ValueKind == JsonValueKind.True
+           || (v.ValueKind == JsonValueKind.String && bool.TryParse(v.GetString(), out var b) && b));
+
+    private static string Truncate(string s) => s.Length <= 300 ? s : s[..300];
+}

Fuchs/Services/InvoiceRecipientAddress.cs

@@ -35,9 +35,18 @@ public sealed class InvoiceRecipientAddress
     /// <summary>Buyer VAT identifier (BT-48). Empty for a private person (B2C).</summary>
     public string VatId { get; set; } = "";
 
+    /// <summary>
+    /// Leitweg-ID / buyer reference (BT-10). When set, the invoice is treated as B2G and emitted
+    /// as <b>XRechnung</b> (the mandatory form for German public authorities); empty for B2B/B2C.
+    /// </summary>
+    public string LeitwegId { get; set; } = "";
+
     /// <summary>True when no VAT id is set — a private person / B2C recipient.</summary>
     public bool IsPrivatePerson => string.IsNullOrWhiteSpace(VatId);
 
+    /// <summary>True when a Leitweg-ID is present — a B2G recipient (→ XRechnung).</summary>
+    public bool IsPublicAuthority => !string.IsNullOrWhiteSpace(LeitwegId);
+
     /// <summary>Reads a structured address from a JSON object (tolerant of missing keys).</summary>
     public static InvoiceRecipientAddress FromJson(JObject? o)
     {
@@ -52,6 +61,7 @@ public sealed class InvoiceRecipientAddress
             City = S(o, "city", "ort"),
             CountryCode = S(o, "countryCode", "country").ToUpperInvariant() is { Length: > 0 } cc ? cc : "DE",
             VatId = S(o, "vatId", "ustid"),
+            LeitwegId = S(o, "leitwegId", "leitweg", "buyerReference"),
         };
     }
 
@@ -78,6 +88,7 @@ public sealed class InvoiceRecipientAddress
         ["city"] = City,
         ["countryCode"] = CountryCode,
         ["vatId"] = VatId,
+        ["leitwegId"] = LeitwegId,
     };
 
     /// <summary>

Fuchs/Services/InvoiceService.cs

@@ -284,7 +284,7 @@ public class InvoiceService : IInvoiceService
         return doc;
     }
 
-    public Task<byte[]> RenderInvoicePdfBytesAsync(FdsInvoiceData invoice, bool draft)
+    public async Task<byte[]> RenderInvoicePdfBytesAsync(FdsInvoiceData invoice, bool draft)
     {
         var doc = GenerateInvoicePdf(invoice, draft);
         // Finalized invoices are emitted as a ZUGFeRD/Factur-X hybrid when eRechnung is enabled:
@@ -292,10 +292,10 @@ public class InvoiceService : IInvoiceService
         // PDF/A-3 layer (ADR 0012). Drafts/previews keep the plain PDF/A. Any failure falls back.
         if (!draft && _erechnung.Enabled)
         {
-            var hybrid = _erechnung.TryBuildHybridPdf(invoice, _pdf.DocToPdfBytesRaw(doc));
-            if (hybrid is { Length: > 0 }) return Task.FromResult(hybrid);
+            var hybrid = await _erechnung.TryBuildHybridPdfAsync(invoice, _pdf.DocToPdfBytesRaw(doc));
+            if (hybrid is { Length: > 0 }) return hybrid;
         }
-        return Task.FromResult(_pdf.DocToPdfBytes(doc));
+        return _pdf.DocToPdfBytes(doc);
     }
 
     public async Task<byte[]> StoreInvoiceDocumentFileAsync(FdsInvoiceData invoice, bool draft,

Fuchs/appsettings.json

@@ -73,9 +73,23 @@
     "ERechnung": {
       "Enabled": false,
       "Profile": "EN16931",
+      "Seller": {
+        "Name": "Sebastian Fuchs GmbH & Co. KG",
+        "Street": "Germaniastraße 15",
+        "PostalCode": "40223",
+        "City": "Düsseldorf",
+        "CountryCode": "DE",
+        "TaxNumber": "106/5849/2962",
+        "VatId": "DE286366012",
+        "LegalRegistrationId": "",
+        "Iban": "DE76300501100045014800",
+        "Bic": "DUSSDEDDXXX",
+        "Email": "info@sanitaerfuchs.de",
+        "Phone": "0211 - 31 07 222"
+      },
       "Validation": {
-        "Enabled": false,
-        "ServiceUrl": "",
+        "Enabled": true,
+        "ServiceUrl": "https://api.processweb.de/api/eInvoice",
         "FailOnError": false
       }
     }

Fuchs/js/intranet/modules/fis.inv_shared.js

@@ -1026,12 +1026,14 @@ $inv.eAddress = function (ev) {
         { name: 'postalCode', label: 'PLZ', type: 'text', value: cur.postalCode || '' },
         { name: 'city', label: 'Ort', type: 'text', value: cur.city || '' },
         { name: 'countryCode', label: 'Land', type: 'select', url: $inv.adrCountries, value: (cur.countryCode || 'DE') },
-        { name: 'vatId', label: 'USt-IdNr. (nur bei Firmen)', type: 'text', value: cur.vatId || '' }
+        { name: 'vatId', label: 'USt-IdNr. (nur bei Firmen)', type: 'text', value: cur.vatId || '' },
+        { name: 'leitwegId', label: 'Leitweg-ID (nur Behörden / B2G)', type: 'text', value: cur.leitwegId || '' }
     ];
     let hint = $$.dc('adr-conformity').append([
         $$.dc('hd').text('Hinweis zur DATEV-/eRechnungs-Konformität'),
         $$.dc('tx').text('Pflicht: Name, Straße, PLZ, Ort und Land. Die USt-IdNr. nur bei Firmen angeben — '
-            + 'für eine Rechnung an eine Privatperson einfach leer lassen.')
+            + 'für eine Rechnung an eine Privatperson einfach leer lassen. Eine Leitweg-ID nur bei '
+            + 'Behörden (B2G) — dann wird die Rechnung automatisch als XRechnung erzeugt.')
     ]);
     $ocms.dlgform(flds, {
         title: 'Rechnungsempfänger',
@@ -1040,7 +1042,8 @@ $inv.eAddress = function (ev) {
             let a = {
                 name: res.name || '', contact: res.contact || '', line2: res.line2 || '',
                 street: res.street || '', postalCode: res.postalCode || '', city: res.city || '',
-                countryCode: (res.countryCode || 'DE'), vatId: ('' + (res.vatId || '')).trim()
+                countryCode: (res.countryCode || 'DE'), vatId: ('' + (res.vatId || '')).trim(),
+                leitwegId: ('' + (res.leitwegId || '')).trim()
             };
             let txt = $inv.composeAddress(a);
             if (ev.data && ev.data.t) { ev.data.t.rwText(txt); }
@@ -1051,12 +1054,46 @@ $inv.eAddress = function (ev) {
     });
 };
 
+/* Leistungsdatum / -zeitraum: structured German-date entry only (no free text). A single date =
+   Leistungsdatum (BT-72); a from+to date = Leistungszeitraum (BG-14). The composed value is a
+   German dd.MM.yyyy string ("18.06.2026" or "01.06.2026 - 30.06.2026") that the PDF shows and the
+   backend maps to the eRechnung service date/period. */
+$inv.provToIso = function (dmy) {
+    let m = ('' + (dmy || '')).match(/(\d{1,2})\.(\d{1,2})\.(\d{4})/);
+    return m ? (m[3] + '-' + ('0' + m[2]).slice(-2) + '-' + ('0' + m[1]).slice(-2)) : '';
+};
+$inv.eProvisionPeriod = function (ev) {
+    let cur = ('' + (ev.data && ev.data.t ? ev.data.t.text() : '')).trim();
+    let dates = cur.match(/\d{1,2}\.\d{1,2}\.\d{4}/g) || [];
+    let flds = [
+        { name: 'von', label: 'Leistungsdatum', type: 'date', value: $inv.provToIso(dates[0] || '') },
+        { name: 'bis', label: 'Leistungszeitraum – bis (optional)', type: 'date', value: $inv.provToIso(dates[1] || '') }
+    ];
+    let hint = $$.dc('adr-conformity').append([
+        $$.dc('hd').text('Leistungsdatum / -zeitraum'),
+        $$.dc('tx').text('Für ein einzelnes Datum nur „Leistungsdatum" ausfüllen; für einen Zeitraum '
+            + 'zusätzlich das Bis-Datum. Nur strukturierte Datumsauswahl — für die E-Rechnung empfohlen.')
+    ]);
+    $ocms.dlgform(flds, {
+        title: 'Leistungsdatum / -zeitraum',
+        addcontent: hint,
+        success: function (res) {
+            let v = ('' + (res.von || '')).trim(), b = ('' + (res.bis || '')).trim();
+            let txt = v === '' ? '' : ((b === '' || b === v) ? v : (v + ' - ' + b));
+            if (ev.data && ev.data.t) { ev.data.t.rwText(txt); }
+            if (typeof (ev.data || {}).change === 'function') { ev.data.change(txt); }
+            $inv.d.sync({ Target: 'provisionperiod', Value: txt });
+        }
+    });
+};
+
 $inv.eHtml = function (ev) {
-    /* The recipient address is edited through the structured dialog whenever an invoice draft is
-       active; reminders (no invoice draft token) keep the plain free-text editor. */
-    if (ev.data && !(ev.data instanceof jQuery) && ev.data.nme === 'invoiceaddress'
-        && $inv.d && typeof $inv.d.token === 'function' && $inv.d.token() !== '') {
-        return $inv.eAddress.call(this, ev);
+    /* The recipient address and the service date/period are edited through structured dialogs
+       whenever an invoice draft is active; reminders (no invoice draft token) keep the plain
+       free-text editor. */
+    if (ev.data && !(ev.data instanceof jQuery) && $inv.d && typeof $inv.d.token === 'function' && $inv.d.token() !== '') {
+        if (ev.data.nme === 'invoiceaddress') { return $inv.eAddress.call(this, ev); }
+        if (ev.data.nme === 'provisionperiod') { return $inv.eProvisionPeriod.call(this, ev); }
     }
     let t = $(this), frmct = ev.data instanceof jQuery ? ev.data : ev.data.t;
     /* Single-line fields must stay plain text — the TinyMCE/html editor wraps the value in <p>

Fuchs/wwwroot/web/fis.inv.de.js

@@ -1569,12 +1569,14 @@ $inv.eAddress = function (ev) {
         { name: 'postalCode', label: 'PLZ', type: 'text', value: cur.postalCode || '' },
         { name: 'city', label: 'Ort', type: 'text', value: cur.city || '' },
         { name: 'countryCode', label: 'Land', type: 'select', url: $inv.adrCountries, value: (cur.countryCode || 'DE') },
-        { name: 'vatId', label: 'USt-IdNr. (nur bei Firmen)', type: 'text', value: cur.vatId || '' }
+        { name: 'vatId', label: 'USt-IdNr. (nur bei Firmen)', type: 'text', value: cur.vatId || '' },
+        { name: 'leitwegId', label: 'Leitweg-ID (nur Behörden / B2G)', type: 'text', value: cur.leitwegId || '' }
     ];
     let hint = $$.dc('adr-conformity').append([
         $$.dc('hd').text('Hinweis zur DATEV-/eRechnungs-Konformität'),
         $$.dc('tx').text('Pflicht: Name, Straße, PLZ, Ort und Land. Die USt-IdNr. nur bei Firmen angeben — '
-            + 'für eine Rechnung an eine Privatperson einfach leer lassen.')
+            + 'für eine Rechnung an eine Privatperson einfach leer lassen. Eine Leitweg-ID nur bei '
+            + 'Behörden (B2G) — dann wird die Rechnung automatisch als XRechnung erzeugt.')
     ]);
     $ocms.dlgform(flds, {
         title: 'Rechnungsempfänger',
@@ -1583,7 +1585,8 @@ $inv.eAddress = function (ev) {
             let a = {
                 name: res.name || '', contact: res.contact || '', line2: res.line2 || '',
                 street: res.street || '', postalCode: res.postalCode || '', city: res.city || '',
-                countryCode: (res.countryCode || 'DE'), vatId: ('' + (res.vatId || '')).trim()
+                countryCode: (res.countryCode || 'DE'), vatId: ('' + (res.vatId || '')).trim(),
+                leitwegId: ('' + (res.leitwegId || '')).trim()
             };
             let txt = $inv.composeAddress(a);
             if (ev.data && ev.data.t) { ev.data.t.rwText(txt); }
@@ -1594,12 +1597,46 @@ $inv.eAddress = function (ev) {
     });
 };
 
+/* Leistungsdatum / -zeitraum: structured German-date entry only (no free text). A single date =
+   Leistungsdatum (BT-72); a from+to date = Leistungszeitraum (BG-14). The composed value is a
+   German dd.MM.yyyy string ("18.06.2026" or "01.06.2026 - 30.06.2026") that the PDF shows and the
+   backend maps to the eRechnung service date/period. */
+$inv.provToIso = function (dmy) {
+    let m = ('' + (dmy || '')).match(/(\d{1,2})\.(\d{1,2})\.(\d{4})/);
+    return m ? (m[3] + '-' + ('0' + m[2]).slice(-2) + '-' + ('0' + m[1]).slice(-2)) : '';
+};
+$inv.eProvisionPeriod = function (ev) {
+    let cur = ('' + (ev.data && ev.data.t ? ev.data.t.text() : '')).trim();
+    let dates = cur.match(/\d{1,2}\.\d{1,2}\.\d{4}/g) || [];
+    let flds = [
+        { name: 'von', label: 'Leistungsdatum', type: 'date', value: $inv.provToIso(dates[0] || '') },
+        { name: 'bis', label: 'Leistungszeitraum – bis (optional)', type: 'date', value: $inv.provToIso(dates[1] || '') }
+    ];
+    let hint = $$.dc('adr-conformity').append([
+        $$.dc('hd').text('Leistungsdatum / -zeitraum'),
+        $$.dc('tx').text('Für ein einzelnes Datum nur „Leistungsdatum" ausfüllen; für einen Zeitraum '
+            + 'zusätzlich das Bis-Datum. Nur strukturierte Datumsauswahl — für die E-Rechnung empfohlen.')
+    ]);
+    $ocms.dlgform(flds, {
+        title: 'Leistungsdatum / -zeitraum',
+        addcontent: hint,
+        success: function (res) {
+            let v = ('' + (res.von || '')).trim(), b = ('' + (res.bis || '')).trim();
+            let txt = v === '' ? '' : ((b === '' || b === v) ? v : (v + ' - ' + b));
+            if (ev.data && ev.data.t) { ev.data.t.rwText(txt); }
+            if (typeof (ev.data || {}).change === 'function') { ev.data.change(txt); }
+            $inv.d.sync({ Target: 'provisionperiod', Value: txt });
+        }
+    });
+};
+
 $inv.eHtml = function (ev) {
-    /* The recipient address is edited through the structured dialog whenever an invoice draft is
-       active; reminders (no invoice draft token) keep the plain free-text editor. */
-    if (ev.data && !(ev.data instanceof jQuery) && ev.data.nme === 'invoiceaddress'
-        && $inv.d && typeof $inv.d.token === 'function' && $inv.d.token() !== '') {
-        return $inv.eAddress.call(this, ev);
+    /* The recipient address and the service date/period are edited through structured dialogs
+       whenever an invoice draft is active; reminders (no invoice draft token) keep the plain
+       free-text editor. */
+    if (ev.data && !(ev.data instanceof jQuery) && $inv.d && typeof $inv.d.token === 'function' && $inv.d.token() !== '') {
+        if (ev.data.nme === 'invoiceaddress') { return $inv.eAddress.call(this, ev); }
+        if (ev.data.nme === 'provisionperiod') { return $inv.eProvisionPeriod.call(this, ev); }
     }
     let t = $(this), frmct = ev.data instanceof jQuery ? ev.data : ev.data.t;
     /* Single-line fields must stay plain text — the TinyMCE/html editor wraps the value in <p>

Fuchs/wwwroot/web/fis.req.de.js

@@ -1550,12 +1550,14 @@ $inv.eAddress = function (ev) {
         { name: 'postalCode', label: 'PLZ', type: 'text', value: cur.postalCode || '' },
         { name: 'city', label: 'Ort', type: 'text', value: cur.city || '' },
         { name: 'countryCode', label: 'Land', type: 'select', url: $inv.adrCountries, value: (cur.countryCode || 'DE') },
-        { name: 'vatId', label: 'USt-IdNr. (nur bei Firmen)', type: 'text', value: cur.vatId || '' }
+        { name: 'vatId', label: 'USt-IdNr. (nur bei Firmen)', type: 'text', value: cur.vatId || '' },
+        { name: 'leitwegId', label: 'Leitweg-ID (nur Behörden / B2G)', type: 'text', value: cur.leitwegId || '' }
     ];
     let hint = $$.dc('adr-conformity').append([
         $$.dc('hd').text('Hinweis zur DATEV-/eRechnungs-Konformität'),
         $$.dc('tx').text('Pflicht: Name, Straße, PLZ, Ort und Land. Die USt-IdNr. nur bei Firmen angeben — '
-            + 'für eine Rechnung an eine Privatperson einfach leer lassen.')
+            + 'für eine Rechnung an eine Privatperson einfach leer lassen. Eine Leitweg-ID nur bei '
+            + 'Behörden (B2G) — dann wird die Rechnung automatisch als XRechnung erzeugt.')
     ]);
     $ocms.dlgform(flds, {
         title: 'Rechnungsempfänger',
@@ -1564,7 +1566,8 @@ $inv.eAddress = function (ev) {
             let a = {
                 name: res.name || '', contact: res.contact || '', line2: res.line2 || '',
                 street: res.street || '', postalCode: res.postalCode || '', city: res.city || '',
-                countryCode: (res.countryCode || 'DE'), vatId: ('' + (res.vatId || '')).trim()
+                countryCode: (res.countryCode || 'DE'), vatId: ('' + (res.vatId || '')).trim(),
+                leitwegId: ('' + (res.leitwegId || '')).trim()
             };
             let txt = $inv.composeAddress(a);
             if (ev.data && ev.data.t) { ev.data.t.rwText(txt); }
@@ -1575,12 +1578,46 @@ $inv.eAddress = function (ev) {
     });
 };
 
+/* Leistungsdatum / -zeitraum: structured German-date entry only (no free text). A single date =
+   Leistungsdatum (BT-72); a from+to date = Leistungszeitraum (BG-14). The composed value is a
+   German dd.MM.yyyy string ("18.06.2026" or "01.06.2026 - 30.06.2026") that the PDF shows and the
+   backend maps to the eRechnung service date/period. */
+$inv.provToIso = function (dmy) {
+    let m = ('' + (dmy || '')).match(/(\d{1,2})\.(\d{1,2})\.(\d{4})/);
+    return m ? (m[3] + '-' + ('0' + m[2]).slice(-2) + '-' + ('0' + m[1]).slice(-2)) : '';
+};
+$inv.eProvisionPeriod = function (ev) {
+    let cur = ('' + (ev.data && ev.data.t ? ev.data.t.text() : '')).trim();
+    let dates = cur.match(/\d{1,2}\.\d{1,2}\.\d{4}/g) || [];
+    let flds = [
+        { name: 'von', label: 'Leistungsdatum', type: 'date', value: $inv.provToIso(dates[0] || '') },
+        { name: 'bis', label: 'Leistungszeitraum – bis (optional)', type: 'date', value: $inv.provToIso(dates[1] || '') }
+    ];
+    let hint = $$.dc('adr-conformity').append([
+        $$.dc('hd').text('Leistungsdatum / -zeitraum'),
+        $$.dc('tx').text('Für ein einzelnes Datum nur „Leistungsdatum" ausfüllen; für einen Zeitraum '
+            + 'zusätzlich das Bis-Datum. Nur strukturierte Datumsauswahl — für die E-Rechnung empfohlen.')
+    ]);
+    $ocms.dlgform(flds, {
+        title: 'Leistungsdatum / -zeitraum',
+        addcontent: hint,
+        success: function (res) {
+            let v = ('' + (res.von || '')).trim(), b = ('' + (res.bis || '')).trim();
+            let txt = v === '' ? '' : ((b === '' || b === v) ? v : (v + ' - ' + b));
+            if (ev.data && ev.data.t) { ev.data.t.rwText(txt); }
+            if (typeof (ev.data || {}).change === 'function') { ev.data.change(txt); }
+            $inv.d.sync({ Target: 'provisionperiod', Value: txt });
+        }
+    });
+};
+
 $inv.eHtml = function (ev) {
-    /* The recipient address is edited through the structured dialog whenever an invoice draft is
-       active; reminders (no invoice draft token) keep the plain free-text editor. */
-    if (ev.data && !(ev.data instanceof jQuery) && ev.data.nme === 'invoiceaddress'
-        && $inv.d && typeof $inv.d.token === 'function' && $inv.d.token() !== '') {
-        return $inv.eAddress.call(this, ev);
+    /* The recipient address and the service date/period are edited through structured dialogs
+       whenever an invoice draft is active; reminders (no invoice draft token) keep the plain
+       free-text editor. */
+    if (ev.data && !(ev.data instanceof jQuery) && $inv.d && typeof $inv.d.token === 'function' && $inv.d.token() !== '') {
+        if (ev.data.nme === 'invoiceaddress') { return $inv.eAddress.call(this, ev); }
+        if (ev.data.nme === 'provisionperiod') { return $inv.eProvisionPeriod.call(this, ev); }
     }
     let t = $(this), frmct = ev.data instanceof jQuery ? ev.data : ev.data.t;
     /* Single-line fields must stay plain text — the TinyMCE/html editor wraps the value in <p>