[Roadmap 21.9] DATEV skill (Unternehmen Online + Belegtransfer + Buchhaltung)

[furukama]

DATEV skill — DATEV is the dominant German SME accounting / payroll / tax-prep platform. Tens of thousands of German Steuerberater (tax advisors) and SMEs run on DATEV daily. An agent that integrates with DATEV unlocks the entire German Mittelstand bookkeeping workflow.

Manifesto: Principle I — the skills are the product. For German SMEs, DATEV is the work.

Why this is high-value

• German SMEs typically split bookkeeping between an in-house operator and an external Steuerberater (tax advisor) — DATEV is the shared exchange surface.
• "Submit the receipts to my Steuerberater" is a daily SME chore that's manual today.
• DATEV API + DATEV Unternehmen Online + DATEV Belegtransfer expose programmable interfaces; OAuth + machine-credential auth supported.
• Strategic moat: US-anchored agent platforms don't speak DATEV. This is a defensibility lever for the German market.

Use cases

• "Pull the open AR positions from DATEV and post a reminder Slack message to the sales team."
• "Submit time-tracking entries for the bookkeeping period (Lohn und Gehalt)."
• "Sync incoming invoice PDFs to DATEV Belegtransfer with the right Buchungskonto."
• "Generate the BWA (Betriebswirtschaftliche Auswertung) for the management meeting."
• "Export the journal entries for the Q4 tax filing."
• "Forward this scanned receipt to my Steuerberater via DATEV Unternehmen Online."

Modules in scope

• DATEV Unternehmen Online — cloud document/data exchange (highest-frequency surface for SME operators).
• DATEV Belegtransfer — receipt/invoice exchange with the Steuerberater.
• DATEV Buchhaltung API (REST) — for read/write to bookkeeping where available.
• Out of scope (initial): DATEV Lohn und Gehalt full payroll automation, DATEV Anwalt — these are large enough to justify their own follow-up tickets if demand emerges.

Acceptance criteria

• R21.1-compliant SKILL.md package; metadata.hybridclaw.category: development (or new accounting).
• DATEV OAuth + API credentials in the encrypted runtime secret store; tokens never seen by the model (Principle VII).
• Conservative-by-default writes (booking entries, payroll submissions require explicit operator grant or confirm-each autonomy).
• Eval suite: 30+ representative scenarios across receipt-transfer, AR/AP queries, and reporting paths.
• Cost-per-run measured in UsageTotals.
• Operator docs covering DATEV tenant setup, API enablement, role/permission scoping.

Depends on

• R21.1 #579 ✅ — skill packaging + lifecycle framework
• R21.2 #580 (PR #642) — OAuth token-binding pattern this reuses

Priority

P1 — strategic for German B2B/SME positioning. Pairs naturally with R25 (EU deployment) for sovereign-cloud-anchored German prospects.