German Travel Expense Law. Deterministically Automated.
We have encoded §9 Abs. 4a EStG, 180+ BMF country-specific per diem rates, the three-month rule, meal deduction logic and collective agreement provisions into an auditable rule engine. No LLM decides on amounts — deterministic decision tables, versioned and audit-proof.
The Engine
One Rule Engine. Every Industry.
The core is always the same: German tax law, deterministically cast into decision tables. Complexity comes from the industry — collective agreements, border crossings, project logic or sheer volume. The engine handles all of them.
Deterministic Decision Tables
Versioned rule sets for per diems, deductions, tax exemptions. Same input + same rule version = same result. No randomness, no LLM output, no black box.
Micro-Decision Audit Trail
Every case is decomposed into 40–120 individual decisions. Each documented: rule, input, result, timestamp, actor. Append-only, reproducible via input hash.
AI Extraction, Not AI Decisions
LLMs read receipts, classify edge cases, generate reasoning text. But amounts, per diems, tax treatment — that is decided exclusively by the rule engine.
BMF Country Per Diems (180+ Countries)
Updated annually, historically versioned. Daily and overnight rates, third-country special rules, pro-rata calculation for midnight border crossings.
Three-Month Rule & Deduction Logic
Automatic monitoring of the 3-month threshold under §9 Abs. 4a EStG. Interruption logic, deductions for employer-provided meals, benefit-in-kind values — all rule-based.
Retroactive Changes
Collective agreement renegotiations, BMF updates, works agreement amendments — the engine recalculates retroactively with a complete audit trail.
Decide, Don't Escalate
The agent books and documents its reasoning. No review gate, no approval workflow. Employees have veto rights — not an obligation to confirm.
Minimal Queries
Only when an audit-proof decision is impossible without information. Then one question, mobile-optimized, with pre-filled options. No 20-field form.
Audit by Design
Every micro-decision generates a decision record — append-only, signed, reproducible. Not documented after the fact, but created within the process.
Process
From Receipt to Posting — in Seconds
Four steps. No manual entry, no lookups, no waiting for approvals.
Data Consolidation
Source systems deliver automatically: duty rosters, credit card feeds, hotel data, receipts. The agent matches — not the employee.
Micro-Decisions
The engine decomposes every case into individual decisions: per diem, deduction, tax exemption, collective agreement. Each deterministic, each documented.
Query Only When Required
Only when an audit-proof decision is impossible without information. Mobile, one question, pre-filled options. Otherwise: posting + notification + veto option.
Export & Audit Pack
Posting-ready export to SAP, DATEV or any ERP system. Complete decision record for every case — tax audit ready at any time.
Crew Rosters, Collective Agreements, 180 Country Per Diems — Fully Automated
When cockpit, cabin and ground crew travel by definition, travel expense processing is not a form problem — it is a governance problem. The engine calculates automatically from duty rosters, applies collective agreement provisions and generates audit-proof postings.
Crew Duty Logic
- Duty roster import from crew planning systems (AIMS, Jeppesen, CKMS)
- Layover detection — city, country, duration automatically from rotation plan
- Split-duty handling — duty interruption, rest period logic, split assignments
- Deadhead recognition — positioning flights, tax treatment as business travel
- IROP automation — delays, hotel changes, crew repositioning, additional layovers
- Crew meal recognition — provided onboard catering → automatic per diem deduction
- Night flight logic — date changes at border crossing, pro-rata per diems
- Reserve crew handling — standby assignment vs. actual flight
Collective Agreements & Works Council
- Union group mapping — cockpit (VC), cabin (UFO), ground, maintenance with separate rule sets
- Union override tables — collectively agreed expense rates override statutory per diems
- Layover provisions per collective agreement — hotel standards, meal supplements, rest period requirements
- Works agreement layer — carrier-wide additional rules on top
- Versioned decision tables — retroactive recalculation after collective agreement renegotiation
- Historization — which agreement version applied at the time of travel? Fully documented
- Multi-carrier logic — different subsidiaries, different agreements, one engine
- Works council reporting — transparency on applied rules per union group
Tax & Finance
- Per diem engine — 180+ country rates, BMF annual updates, historically versioned
- Three-month rule — automatic monitoring, interruption logic, threshold warning
- Meal deductions — breakfast/lunch/dinner, employer-provided vs. self-paid, benefit-in-kind values
- Staff travel benefit-in-kind — §8 Abs. 2 vs. §8 Abs. 3 EStG, discount threshold calculation
- Multi-currency — credit card rate → ECB reference rate → daily rate, rate hierarchy
- EU VAT recovery — automatic identification of recoverable hotel invoices
- Shadow payroll trigger — permanent establishment detection, 183-day rule for international bases
- Tax-free vs. taxable components — clean separation for payroll export
- Corporate card matching — AirPlus, Amex, Visa Business feed, advance settlement
- Hotel direct billing — contracted hotel vs. self-booked, ancillary cost separation
Anomaly Detection
- Comparison against crew collective — statistical outliers in expenses
- Hotel price anomalies — deviation from contracted hotel level
- Duplicate claim detection — same route, same date, different case
- Unusual layover patterns — deviation from roster
- Anomaly as signal — ML detects, rule engine decides
Source System Integration
- Crew planning systems (AIMS, Jeppesen, CKMS)
- Corporate card feeds (AirPlus, Amex, Visa Business)
- Hotel contract management systems
- SAP HR / SAP HCM / SuccessFactors
- SAP FI — posting-ready export
Employee Experience
- Zero-touch crew mode — settlement from roster, no manual entry
- Push notification — "Your travel expenses for rotation FRA–JFK–FRA have been calculated"
- Veto model instead of approval — employee does not confirm, but can object
- Mobile queries — one question, pre-filled, answered in 10 seconds
- Transparent calculation — every per diem, every deduction visible
Client Logic, Cost Pass-Through, Hierarchy-Based Policies
In consulting firms, every trip has dual allocation: tax-compliant and client-billable. The engine separates both automatically and applies travel policies by hierarchy level, project and client contract.
Project & Client
- Project allocation per trip — automatic from calendar, booking system or manual
- Client-specific cost logic — what is billable, what does the firm absorb?
- Client-contractual travel rules — caps, permitted classes, pre-approval
- Split billing — internal / client / project overhead cleanly separated
- Project controlling integration — travel costs flow into contribution margin
- Cross-charge between entities / offices
Policy & Hierarchy
- Travel policy per hierarchy level — Partner, Manager, Consultant, Analyst
- First/business class rules — from which flight duration, which level, which project?
- Hotel price limits per city — dynamic or fixed, with exception logic
- Approval thresholds by cost — automatic vs. approval
- Entertainment expense validation — 70/30 rule, mandatory field checks
- Frequent flyer policy — private use of business miles
Tax & Compliance
- 3-month rule monitoring for changing project locations
- Double household logic — detection, cost allocation, tax allowances
- Input VAT extraction — domestic, EU, third-country differentiated
- Corporate card reconciliation with receipt matching
- DATEV / SAP / Oracle FI export
- Anomaly detection for unusual travel patterns
- Audit documentation for client engagements
Anomaly & Compliance Intelligence
- Travel pattern analysis per consultant — deviations from project cluster norms
- Policy violation scoring — not binary (yes/no), but weighted by severity
- Entertainment compliance — attendee list, occasion, 70/30 split automatically verified
- Duplicate booking detection — same client, same date, different cost centers
- Seasonal patterns — quarter-end spikes, budget burn-down effects
- Benchmark against hierarchy peers — Partner vs. Partner, Manager vs. Manager
Source System Integration
- ERP systems (SAP, Oracle, Microsoft Dynamics)
- Travel booking systems (BCD, CWT, Amex GBT)
- Calendar integration (Outlook, Google) for project allocation
- Credit card feeds (Amex, Visa Business, Diners Club)
- HR master data (SuccessFactors, Workday, Personio)
- DATEV / SAP FI — posting-ready export with client split
Consultant Experience
- Project mode — trip automatically assigned to active project
- Photo receipt instead of form — smartphone photo, OCR, done
- Approval status tracker — where is my expense report stuck?
- Multi-project weeks — automatic split when switching projects within a week
- Weekly settlement mode — all trips of a week bundled
- Transparent calculation — every policy application, every deduction visible
Border Crossings, Shift Models, EU Mobility Package
When truck drivers cross multiple country borders daily, every minute becomes a tax event. The engine calculates per diems to the second based on location — GPS-based, shift-model integrated, EU Mobility Package compliant.
Route & Time
- GPS-based country detection — automatic location determination
- Border crossing timestamp tracking — to-the-second for per diem calculation
- 24h vs. calendar day logic — both calculation methods configurable
- Multi-day tour handling — connected tours as one case
- Tachograph data integration for driving time verification
- Night driving logic — date change during transit
Labor Law & EU
- EU Mobility Package compliance — Posted Workers Directive, cabotage, documentation
- Driver shift model integration — driving and rest periods
- Vehicle overnight vs. hotel — different reimbursement rates
- Night supplement recognition — automatic from shift data
- Weekend/holiday logic — country-specific
- Authority compliance export — BAG, BALM, EU inspections
Per Diems & Payroll
- Per diems by deployment country — automatically derived from GPS data
- Tax-free allowances — correct separation tax-free / taxable
- Meal allowances with deduction logic
- Payroll interface — tax-free components correctly transmitted
- Retroactive legislative updates — EU package, BMF, national rules
- Complete decision reasoning per trip
Anomaly & Fraud Detection
- Route plausibility — GPS track vs. reported route
- Fuel receipts vs. driving distance — consumption plausibility
- Overnight anomalies — hotel invoice vs. vehicle location
- Duplicate claim detection — same route, same date
- Collective comparison — driver peer group analysis
- Anomaly as signal — ML detects, rule engine decides on escalation
Source System Integration
- Telematics systems (Fleetboard, TomTom, Trimble)
- Dispatch systems (Transporeon, TimoCom, CarLo)
- Tachograph data (VDO, Stoneridge)
- Fuel card feeds (DKV, UTA, Shell Card)
- HR systems (SAP HR, DATEV Payroll, Sage)
- SAP FI / DATEV — posting-ready export with cost center split
Driver Experience
- Zero-touch driver mode — settlement from telematics + GPS, no form
- Push notification — "Your per diems for tour DE–PL–CZ have been calculated"
- Veto model — driver can object, does not have to confirm
- Language-independent — interface in driver's language, settlement in company language
- Mobile-first — one question, pre-filled, answered in 10 seconds
- Transparent calculation — every per diem, every border crossing visible
High Volume, Strict Policies, Automatic Compliance
Thousands of field employees, each with a company car, hotel stays and entertainment receipts. Individual complexity is lower, but at 10,000+ cases per month the automation rate decides millions.
Vehicle & Mileage
- Company car vs. private car — automatic detection from master data
- 1% rule vs. logbook — trigger logic when logbook is more favorable
- Mileage allowance engine — €0.30/km, tiered rates, limits
- CRM integration — client visit → trip automatically linked
- Route plausibility check — distance vs. reported kilometers
Policy & Governance
- Hotel & flight price policy checks — automatically validated against limits
- Cost center auto-mapping — from org structure, project, region
- Manager approval logic — from threshold, via push
- Budget limit monitoring — per cost center, employee, period
- Entertainment expense ratio 70/30 — automatic split and validation
- Fraud pattern detection — duplicate bookings, patterns, outliers
Tax & Export
- Digital receipt verification — OCR + plausibility + mandatory field checks
- Input VAT verification — domestic, EU, third-country, reverse charge
- Domestic/international per diems — BMF-compliant calculation
- Credit card reconciliation — corporate card feed, receipt matching
- DATEV / SAP / Oracle FI export
- Dashboard for HR & Finance — costs, compliance, anomalies
Anomaly & Compliance Intelligence
- Travel pattern analysis per sales territory — deviations from region norms
- Entertainment compliance — attendee list, business occasion, 70/30 split automatically verified
- Mileage plausibility — GPS vs. reported, jumps, gaps
- Hotel price anomalies — deviation from city limits
- Budget burn rate warning — per cost center, per employee
- Quarterly pattern detection — quarter-end peaks, unusual clusters
Source System Integration
- CRM systems (Salesforce, Microsoft Dynamics, SAP CRM)
- Fleet management (LeasePlan, ALD, Alphabet)
- Credit card feeds (Amex, Visa Business, Mastercard Corporate)
- Travel booking systems (BCD, CWT, Amex GBT)
- HR systems (SAP HR, SuccessFactors, Workday)
- SAP FI / DATEV / Oracle FI — posting-ready export
Field Sales Experience
- Photo receipt instead of form — smartphone photo, OCR, automatic assignment
- CRM link — client visit → trip automatically linked and categorized
- Weekly settlement mode — all trips of a week bundled, one click
- Push status — "Your expense report for CW 12 has been posted"
- Veto model — employee can object, does not have to confirm
- Transparent calculation — every per diem, every policy application visible
Security & Compliance
Enterprise Security. Not Retrofitted.
Built from the ground up for regulated environments. Not bolted on as a feature — engineered as an architectural principle.
EU Data Residency
All data remains in EU data centers. No processing in the US. No US Cloud Act exposure for personal employee data. Hosted on European infrastructure.
GDPR by Design
Anonymization instead of deletion — compatible with tax retention periods (10 years, AO §147) and GDPR Art. 17. Granular consent management. No conflict between tax law and data protection.
EU AI Act Compliant
Clear architectural separation: LLM for data extraction, rule engine for decisions. No black box over tax matters. Field-level traceability — every decision reconstructable.
Audit Trail (append-only)
Every micro-decision generates a signed decision record. Input hash + rule version = reproducible result. Sealed audit packs (JSON + PDF, SHA-256). Tax audit ready at any time.
ISO 27001 / PS 951
Architecture is cert-ready — integrated controls registry, automated evidence runs, versioned policies. No retroactive documenting — compliance in live operations.
SSO & Tenant Isolation
Integration with existing identity providers. Tenant isolation at database level (row-level security). Role model: admin, auditor, clerk, employee — granularly configurable.
How Complex Is Your Travel Expense Challenge?
In 30 minutes we analyze your collective agreements, legal jurisdictions and receipt types — and show you what the engine already covers today.
Free Potential AnalysisFrequently Asked Questions
Does the engine replace existing ERP systems like SAP or DATEV?
No. The engine sits between source systems and ERP. It reads data from duty rosters, credit card feeds and receipts, makes deterministic decisions and delivers posting-ready results to SAP, DATEV or Oracle FI.
What happens when German tax law changes or new BMF per diem rates are published?
Decision tables are versioned. New rule sets are deployed as separate versions — with validity periods. Retroactive changes (e.g., collective agreement renegotiations) trigger automatic recalculation of all affected cases.
How does the engine differ from SAP Concur or other expense tools?
Concur is a capture and workflow tool. The Gosign engine is a decision engine for German tax law. Concur requires employees to fill forms and approvers to sign off. The engine needs neither — it decides deterministically from source system data.
Is the system compatible with German works council requirements?
Yes. Every decision is auditable, the rule set is inspectable, and the complete audit trail is accessible to the works council. The engine makes no opaque AI decisions — it applies documented rules.
Does data leave the organization?
No. The engine runs in EU data centers with full data residency. Personal data is processed exclusively within the EU. No US Cloud Act exposure.