Pay-per-invoice XRechnung/ZUGFeRD generator with GoBD-konformes Archiv built-in — no subscription, no full-Buchhaltung overhead. Validates EU-Norm EN 16931 in real time, embeds Leitweg-ID for B2G, exports DATEV-CSV for the user's Steuerberater. €0.99/invoice one-shot or €5/mo unlimited.

What we ship

**Core features (MVP)**

• Drag-drop PDF invoice → auto-extract fields → XRechnung 3.0 / ZUGFeRD 2.3 PDF/A-3 output
• Real-time EN 16931 validation + Leitweg-ID picker for B2G recipients (all Bundesländer)
• VIES UStID validation inline (green/red badge before sending)
• Pay-per-invoice meter visible in header (€0.99/invoice) with €5/mo unlimited upgrade option
• GoBD-ready archive with one-click "Download ZIP for period" button (10-year retention, audit-trail)

**Primary user flow**

1. User lands on homepage, drag-drops a PDF draft invoice (or fills the form from scratch)

2. Picks recipient: B2G (Leitweg-ID dropdown by Bundesland) or B2B (UStID + VIES check)

3. Previews validated XRechnung XML + embedded ZUGFeRD PDF — clicks "Bezahlen & Senden" (€0.99 Stripe single-charge)

4. Downloads file, optionally one-click email to recipient; invoice auto-lands in GoBD archive

**What it looks like**

• **Landing**: "XRechnung & ZUGFeRD — €0.99 per invoice, ohne Abo". Hero is a drag-drop PDF zone with live-preview to the right, beneath it a counter "Bereits 2,341 Rechnungen heute erstellt". Trust badges: EN 16931 / GoBD-ready / DATEV-CSV. FAQ on §34a UStDV (KU and B2G).
• **Main app**: 3-column workspace — left invoice list (status: Draft/Validated/Sent/Archived), center invoice editor with inline validation and Leitweg-ID picker, right XRechnung XML preview + ZUGFeRD PDF render. Top bar: pay-per-invoice counter and "Upgrade auf €5/mo unlimited" CTA.
• **Output**: ZIP file with two artifacts — `RECHNUNG_2026-001.xml` (XRechnung 3.0 EN 16931 compliant) and `RECHNUNG_2026-001.pdf` (ZUGFeRD 2.3 PDF/A-3 with embedded XML). Optional DATEV-CSV export for the Steuerberater. GoBD-Archiv page: table of all invoices filterable by year + "Jahresarchiv ZIP herunterladen" button.

**MVP build plan** — 10 days

Source signals

• **SIG-20260425-dach-micro-saas-utility-zugferd-local-converter** — "Da ich keine 20€/Monat für Buchhaltungstools zahlen wollte, habe ich mir ein kleines Tool gebaut" (RECURRING)
• **SIG-20260425-dach-micro-saas-utility-e-rechnung-2028-kleinunternehmer** — "wie groß heute schon der Bedarf nach einfachen E-Rechnungslösungen ist" (RECURRING)
• **SIG-20260425-dach-micro-saas-utility-rechnungspilot-open-source-demand** — AGPL-3.0 wishlist enumerates 4 structural complaints (RECURRING)
• **SIG-20260425-dach-micro-saas-utility-papierkram-free-tier-leverage** — "100% kostenlosen Basic-Plan ideal für Solo-Freelancer" (RECURRING)
• **SIG-20260425-dach-micro-saas-utility-lexoffice-price-fatigue** — "E-Rechnungsfunktion nur im XL-Tarif (32,90€)" (RECURRING)

Reasoning

Five signals converge on one pain: DACH freelancers refuse subscription pricing for a tool they only need a few times a year, and Lexoffice gates the function behind their most expensive tier. The market is explicitly asking for itself (the r/selbststaendig OP literally surveys demand). Stack-fit is clean: Cloudflare Pages + Railway + FastAPI + Postgres + Stripe + open-source XRechnung/ZUGFeRD libraries (KoSIT, Mustang) — buildable in 10 days solo. The competitive distinction is positioning: free competitors (kostenlose-erechnung.de) cap usage at 3/month and hide GoBD-archive behind paywall; we include GoBD-archive in the free tier and only paywall unlimited usage + DATEV export. Honest freemium beats trial-locked freemium in a market where the free tier IS the entry-bar (per SIG-papierkram).

Quick competitive read

5 profiled competitors (CMP files):

• **kostenlose-erechnung.de** — free up to 3/mo, €9.90/mo unlimited + GoBD-archive. Strongest direct competitor.
• **easybill** — €9 Solo full suite includes XRechnung+GoBD; €19/€39 upmarket.
• **Lexoffice (Lexware Office)** — €32.90 XL gates XRechnung; canonical pain-point we exploit.
• **sevDesk E-Rechnungsgenerator** — free generator as honeypot for €13.90+ Buchhaltung.
• **RechnungsPilot (AGPL-3.0)** — self-host for developer-freelancers, not our non-technical Kleinunternehmer.

Market density: **medium (saturated free-tier)** but **white-space at honest pay-per-invoice + GoBD-archive in free**. No competitor monetizes per-invoice — they all push subscription or free-with-paywall-archive. Regulatory soft-block (GoBD cert €5K) is the moat — small, but real for episodic clones. Competitive_pressure: 3 (low-medium).

Initial pricing hypothesis

Freemium mandatory per DACH norms: €0 (3 invoices/mo, GoBD-archive included) → €0.99 per-invoice one-shot → €5/mo unlimited + DATEV-CSV + multi-Mandant → €15/mo Pro for micro-agencies. Deliberately below the €10-100/mo developed-tier WTP band to capture price-sensitive Kleinunternehmer and lead-gen for upsell.

Distribution hypothesis

Primary: SEO (XRechnung erstellen, Kleinunternehmer §19 UStG long-tail) + r/selbststaendig + r/Steuern community presence + DATEV-Partnerprogramm integration (per SIG-circula one-partner-to-millions-ARR pattern in DACH). Secondary: Product Hunt DE + Indie Hackers launch.