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Ironfang

Financewolf

E-invoice validation

Validate.
Understand. Fix.

Check UBL invoices and credit notes against EN 16931 and Peppol BIS Billing 3 rules. Find the failure, understand the rule and fix the source document.

Try the free validator Read the guide

No account needed to try it. Raw invoice XML is never stored.

Financewolf / validation resultExample output

invoice.xml

UBL Invoice / validation completed

Invalid
XML syntaxPassed
UBL schemaPassed
EN 169311 finding
Peppol rulesPassed

BR-CO-10

Line amounts do not add up

The document-level line total must match the sum of the individual line net amounts.

Read the rule explanation
Peppol BIS Billing 3XML never stored

Document validation

A clear path from XML to answers.

One validation result brings the document checks and rule findings together, with the detail you need to take the next step.

Invoices and credit notes

Check UBL Invoice and CreditNote XML against the supported Peppol BIS Billing 3 rulesets. Use the free browser tool or send a request from your application.

Every validation layer

See XML syntax, UBL schema, EN 16931 and Peppol rule results separately. Distinguish an invalid document from a validation service failure.

Findings you can act on

Read the rule identifier and finding, then follow a reviewed explanation where available. Fix the source document and validate it again.

Results you can keep

Download result JSON and a readable report. Signed-in and API results are saved for 30 days, with the option to delete them sooner.

Your first validation

From a finding to a fix.

  1. Choose your document

    Try the sample or upload invoice or credit note XML, up to 5 MiB. The free validator works without an account.

  2. Read the findings

    Follow the verdict through each validation layer. Open the available rule explanations to understand what needs to change.

  3. Fix and validate again

    Update your source document, rerun validation and download the results. Open the readable report to print or save it as a PDF.

Open the free validator

Rule explanations

Understand what went wrong.

Start with the rule, follow its meaning and work back to your document. Explanations come from the same reviewed catalogue as the validator.

Browse the validation guide

BR-CO-10

Line amounts do not add up

The document-level line total must match the sum of the individual line net amounts.

BR-01

The specification identifier is missing

Invoice and CreditNote documents need a non-empty CustomizationID identifying their specification.

PEPPOL-EN16931-R004

Check the billing specification identifier

This rule checks the Peppol Billing identifier prefix and rejects a double-colon sequence in the identifier.

Other rules retain their engine finding and identifier. Explanations are shown where reviewed guidance is available.

Developer workflow

Make validation part of your application.

Send XML over HTTPS and receive structured results. List saved validations, read their findings and delete results through the same API.

OpenAPI contract Integration examples
Financewolf / API workflow

Required key scope:financewolf:einvoices:write

Request

curl --request POST 'https://api.ironfang.uk/financewolf/v1/einvoices/validate' \
  --header 'Authorization: Bearer YOUR_API_KEY' \
  --header 'Content-Type: application/xml' \
  --header 'Accept: application/json' \
  --header 'Idempotency-Key: invoice-2026-001' \
  --data-binary '@invoice.xml'

Example response - excerpt

200 OK
Content-Type: application/json

{
  "operation_id": "019f29a4-3158-7b81-8f64-f1072146de30",
  "status": "completed",
  "outcome": "valid",
  "ruleset": {
    "id": "fwrs_example_invoice_2026a"
  },
  "findings": [],
  "findings_summary": {
    "returned": 0, "total": 0,
    "cap": 1000, "truncated": false
  }
}

Send your XML file as the request body. The optional Idempotency-Key lets you retry the same request without a second validation or charge. Invalid documents also return 200, with outcome: invalid and their findings.

Illustrative responses. Authenticated results are saved for 30 days. Raw XML is never stored.

Questions

Know what your result means.

Do I need an account to try it?
No. The free Peppol validator accepts a sample or your own XML without an account. Create an account when you want saved validation history and API integration.
What happens to my invoice XML?
Raw invoice XML is never stored. Anonymous XML and results are processed transiently. Signed-in and API result JSON and findings are stored for 30 days and can be deleted sooner.
Can I download the result?
Yes. Download JSON and an unsigned readable report. The report can be printed or saved as a PDF from your browser. Downloaded copies stay under your control.
Does a passing result send or certify my invoice?
No. Validation checks supported structured-document rules. It does not send invoices over Peppol, establish participant registration or certify legal or tax compliance.
Read more about saved results and privacy

Less to operate. More to ship.

Start with one document.

Try the sample, understand the findings and bring validation into your workflow.

Try the free validator Create a free account

No account needed for the free validator. Create an account for saved history and API integration.