ADR-002: Financial & Ledger Strategy

Strategic Intent (The "Why")

• Separation of Concerns: Busflow strictly separates operational controlling (sub-ledger) from legal financial accounting (general ledger) to maintain agility and operational flexibility for SMB operators.
• Risk Mitigation: Building a native general ledger introduces massive liability, GoBD certification requirements, and the immense overhead of maintaining constantly changing ELSTER/tax taxonomies.
• Resource Allocation: Engineering resources are explicitly diverted away from monolithic accounting features toward high-impact "10% Differentiators" such as AI-driven automation (Magic Upload), e-commerce checkouts, and dynamic pricing algorithms.

High-Level Architecture & Components

• Operational Sub-Ledger:
  • The system utilizes a CostingSheet for initial margin planning and pre-calculation (Vorabkalkulation).
  • A FinancialLedger handles post-calculation (Nachkalkulation) by aggregating real-time booking revenues, onboard sales, and OCR-extracted expense receipts to provide instant profitability metrics (Soll/Ist-Vergleich) for internal management.
• Automated Tax Engine:
  • A dedicated TaxStrategyType evaluates procurement data autonomously to ensure compliance with European travel tax law.
  • It applies standard VAT (STANDARD_VAT) to internally fulfilled capabilities and own services (Eigenleistungen).
  • It automatically calculates the highly complex margin taxation scheme according to § 25 UStG (MARGIN_SCHEME_25) whenever third-party tourist services (Fremdleistungen) the system detects in the booking.
• Immutability & State Management: To resolve the conflict between dynamic, real-time dispatch modifications and strict accounting compliance, operational records the system subjects to a hard period close (freeze state). Modifications post-freeze the system restricts to explicit cancellation/storno workflows.

External API & Integration Surface

• DATEV & Financial Exports: Fully calculated and tax-resolved transaction records the system bundles at the end of the reporting period and handed off via DATEV-compliant CSV exports or APIs.
• Delegation of Custody: The legal custody, balance sheet generation, and direct communication with tax authorities are explicitly offloaded to the operator's certified tax advisor and external accounting software.

Out of Scope (Explicit Anti-Goals)

• Native General Ledger: Busflow will not operate as a full Double-Entry Bookkeeping system.
• Replacing or Decoupling from DATEV: Busflow does not aim to replace certified external accounting software (DATEV, Agenda, etc.). The platform delegates legal custody, balance sheet generation, and tax authority communication to the operator's Steuerberater.
• Direct Tax Authority APIs: No direct ELSTER or regional tax office data transfer modules will be built.

In Scope (Explicit Inclusions)

• DATEV Integration & Sync: Bidirectional data exchange with DATEV (export of tax-resolved records, import of BWA/SuSa for reconciliation) is a valid and desired integration — it complements the external accounting system instead of replacing it. An automated sync is the natural evolution of the manual Reconciliation Upload (Phase 1 → Phase 2).
• Asynchronous Legal Reporting: Legal accounting data is processed via asynchronous batch aggregation. Real-time millisecond updates are not required for compliance exports.