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Under the hood. LightKasse is designed so you don't have to think about any of this. But if you or your accountant want to know what's in the box — here it is.

1. German legal standards

• KassenSichV · §146a AO — every receipt is signed by a certified Technical Security Element (TSE). We use Fiskaly Cloud TSE.
• GoBD — immutable audit log. Every setting change, every correction (Storno), every void is recorded and cannot be rewritten.
• Belegausgabepflicht — receipts include all 13 mandatory fields.
• DSFinV-K v2.4 — one-click export for tax-office audits (20 CSVs + index.xml + DTD).
• DATEV EXTF v700 — standard Buchungsstapel for your accountant.
• TSE offline rule — up to 48 h offline buffer with automatic re-signing when the cloud TSE is reachable again.

2. Architecture

Sales are written to a local SQLite database first — instant, no spinner, no network dependency. A background worker continuously replicates every transaction to PostgreSQL in the cloud (Supabase or your own Postgres). Two independent copies of every record, every day.

If the internet is down, the register keeps running normally. When the connection returns, the outbox catches up on its own — sales, receipts, TSE signatures, DATEV entries — in the correct order.

3. Payments & hardware

• Card payments — SumUp Cloud API. No extra terminal required beyond a SumUp reader.
• Printers — standard ESC/POS thermal printers are auto-discovered on the local network.
• Register — any modern Mac.

4. API & integrations

• REST / JSON — every sale, product, report and export reachable through a clean, versioned HTTP API.
• Webhooks — subscribe to sale, day-close, storno and inventory events.
• MCP server — a dedicated Model Context Protocol endpoint you can attach to Claude or ChatGPT to ask natural-language questions about your data.
• Weekly release cadence — updates roll out quietly in the background; nothing for you to install.

5. Data & privacy

• Primary data lives on your register (local SQLite).
• Replica lives in the EU (Supabase, Frankfurt · AWS eu-central-1) — or your own PostgreSQL.
• TSE signing happens via Fiskaly (Germany).
• Full export & deletion on request. Your data stays yours.

6. Pricing

€50 / month, per register. Everything above is included — TSE, replication, DSFinV-K & DATEV exports, SumUp integration, printer support, API access, updates. No setup fee. No per-transaction fee. Cancel anytime.

LightKasse is in pre-launch. Details may refine as we harden the product before general availability (Q3 2026).