# KoSIT

German coordination body; commonly refers to the BR-DE validation rules/validator for XRechnung.

## Definition

German coordination body; commonly refers to the BR-DE validation rules/validator for XRechnung.

## Why this term matters

KoSIT publishes the official validator and Schematron rule sets that German federal/state portals (ZRE, OZG-RE) execute on every incoming XRechnung. Reproducing KoSIT validation locally before sending is the single most effective way to avoid B2G rejections and downstream cash-flow delays.

## Explanation

Validation errors are commonly referenced by BR-DE rule IDs.

Useful for troubleshooting why an invoice is rejected.

## Common mistakes

- Validating against the wrong KoSIT scenario — XRechnung-UBL-Invoice and XRechnung-CII have separate Schematron rules; using the UBL ruleset on a CII document hides BR-CO/BR-DE failures.
- Running an out-of-date validator JAR — KoSIT releases follow XRechnung versions (e.g. 1.5.x for XRechnung 3.0.x), and old JARs miss new BR-DE rules.
- Treating warnings as informational — many BR-DE warnings (e.g., suspicious BT-32 SellerTaxRegistrationIdentifier formats) become hard errors in the next XRechnung minor.
- Not bundling the EN 16931 codelist files with the validator — codelist mismatches surface as cryptic CL-* failures rather than business-rule errors.

## Frequently asked questions

### Is the KoSIT validator free?
Yes — KoSIT publishes the validator and rule sets under the Apache 2.0 licence on GitHub (itplr-kosit/validator and itplr-kosit/validator-configuration-xrechnung). It is the same engine ZRE/OZG-RE run server-side.

### How do I read a KoSIT report?
KoSIT outputs an XML report with a top-level acceptance result and per-rule failedAssert entries. Each entry references the rule ID (BR-*, BR-DE-*, BR-CO-*), location (XPath), and a human-readable message — the rule ID is the key to look up the spec.

### Does KoSIT cover Peppol BIS Billing 3.0 too?
KoSIT focuses on XRechnung. For Peppol BIS Billing 3.0 you should additionally run the OpenPEPPOL Schematron rules (PEPPOL-EN16931-*). Many German recipients accept either profile and validate accordingly.

## Related resources

- [KoSIT validator errors](/resources/kosit-validator-errors)

## Related terms

- [Validation](/resources/glossary/validation): Process of checking an e-invoice against syntax rules and business rules.
- [XRechnung](/resources/glossary/xrechnung): German e-invoicing specification for the public sector based on EN 16931.