KoSIT Validator: How to Validate ZUGFeRD and XRechnung Files

The KoSIT Validator (Koordinierungsstelle für IT-Standards — Coordination Office for IT Standards) is the official tool of the German administration for validating e-invoices. Anyone sending ZUGFeRD or XRechnung files should validate them beforehand — a rejected invoice delays payment and causes unnecessary extra work.

> Quick answer: The KoSIT Validator checks e-invoices against XSD schemas, business rules, and German CIUS rules. You can use it as a local Java tool or alternatively use the free ZUGFeRD & XRechnung Validator directly in your browser.

What exactly does the KoSIT Validator check?

The Validator performs five sequential checks:

1. Syntax check: Is the XML well-formed?
2. Schema check: Does the structure conform to the UBL 2.1 or CII schema?
3. Business rules (BR): Are all required fields present? (BR-01 to BR-65)
4. Calculation rules (BR-CO): Do the totals add up? (Net + Tax = Gross)
5. CIUS rules: German-specific rules for XRechnung (BR-DE-01 to BR-DE-25)

Only when all five levels pass is the e-invoice considered valid. A single error at any level results in rejection.

How can I use the KoSIT Validator?

Option 1: Online Validator

Various providers offer the KoSIT Validator as an online tool. You upload your XML file and immediately receive a validation result. The downside: your invoice data is transmitted to an external server.

Option 2: Command line (Java)

The official Validator is a Java program:

1. Install Java Runtime (JRE 11+)
2. Download the Validator ZIP
3. Load the configuration (Scenarios) for XRechnung or ZUGFeRD
4. Run the command: java -jar validationtool.jar -s scenarios.xml file.xml

Option 3: Free browser-based Validator

The ZUGFeRD & XRechnung Validator on our website checks your XML file directly in the browser against all EN 16931 required fields. No installation, no upload — the file never leaves your computer.

What are the most common validation errors?

A complete overview of required fields can be found in EN 16931: All Required Fields.

Why should I validate before sending?

An invalid e-invoice is immediately rejected by government agencies via the ZRE. Companies with automated invoice receipt systems also reject faulty files. The result: delayed payments and unnecessary correction effort.

Validate every e-invoice before sending with the free ZUGFeRD & XRechnung Validator — directly in your browser, without uploading to a server. Alternatively, you can create an XRechnung via the form-based XRechnung Generator — validation is built in.

How does TaxLayer validate automatically?

TaxLayer automatically validates every generated e-invoice against all EN 16931 required fields before the file is available for download. This way, you avoid rejections by the recipient — without a manual validation step. The first two conversions per month are free.