Invoices and credit notes
Check Peppol BIS Billing 3 in UBL, XRechnung in UBL or CII, and ZUGFeRD / Factur-X as a hybrid PDF or its XML. Use the free browser tools or send a request from your application.
Ironfang Finance
E-invoice validation
Validate.
Understand. Fix.
Check Peppol, XRechnung and ZUGFeRD / Factur-X invoices against EN 16931 and each format's official rules. Find the failure, understand the rule and fix the source document.
Other formats: XRechnung or ZUGFeRD / Factur-X. See pricingNo account needed to try it. Anonymous documents and results are not kept.
invoice.xml
UBL Invoice / validation completed
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 explanationPeppol BIS Billing 3Transient XML checks
Document validation
From your document to a clear result.
Every format is checked the same way: one result brings the document checks and rule findings together, names the ruleset that checked it, and tells an invalid document apart from a service failure.
Every validation layer
See each layer separately: the XML and its schema, the format's business rules and, for a hybrid PDF, the PDF/A and attachment checks. 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
Signed-in and API results are saved for 30 days, with the option to delete them sooner. Download the JSON, or turn a retained result into a signed report anyone can verify.
Your first validation
From a finding to a fix.
Choose your document
Open the validator for your format and try its sample, or upload your own invoice or credit note: XML, or a hybrid PDF for ZUGFeRD / Factur-X. No account needed.
Read the findings
Follow the verdict through each validation layer. Open the available rule explanations to understand what needs to change.
Fix and validate again
Update your source document and validate it again. Keep the result, or bring the same check into your application through the API.
Other formats: XRechnung or ZUGFeRD / Factur-X.
Try anonymously
- A Peppol validator, and a JSON playground for Peppol UBL
- An invoice viewer with PDF download
- An XRechnung validator and viewer for UBL and CII, in English and German
- A ZUGFeRD / Factur-X validator for hybrid PDFs and their XML
- Transient results
- No signup required
New to e-invoicing? Explore the e-invoicing learning hub
Build with Ironfang Finance
- API keys and saved validation history
- Jobs, batches and webhooks
- S3-compatible artifact delivery
- SDKs, CLI and automation tooling
Try Ironfang Finance without an account. Create one when you're ready to integrate it: every account has free validations and generations each month, with no card needed.
Create free accountRule 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.
BR-01
The specification identifier is missing
Invoice and CreditNote documents need a non-empty CustomizationID identifying their specification.
BR-CO-10
Line amounts do not add up
The document-level line total must match the sum of the individual line net amounts.
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. Browse all 242 rule explanations.
Developer workflow
Make validation part of your application.
Send an invoice's XML, or a ZUGFeRD / Factur-X PDF, over HTTPS and receive structured results. List saved validations, read their findings and delete results through the same API.
Use the published Python or TypeScript validation SDK, Python CLI or GitHub Action. For durable work, configure signed webhooks and S3-compatible artifact delivery with independent retries. Delivery to your endpoint or bucket does not send an invoice over Peppol.
Integration examples for your account are in the portal.
Required key scope:finance:einvoices:write
Request
curl --request POST \
'https://api.ironfang.com/finance/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 OKContent-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. XRechnung and ZUGFeRD / Factur-X use the V2 route; see the API quickstart.
Required key scope:finance:einvoices:read
Request
curl 'https://api.ironfang.com/finance/v1/einvoices/results' \
--header 'Authorization: Bearer YOUR_API_KEY' \
--header 'Accept: application/json'Example response
200 OKContent-Type: application/json
Cache-Control: no-store
{
"results": [
{
"operation_id": "019f29a4-3158-7b81-8f64-f1072146de30",
"outcome": "valid",
"ruleset_id": "fwrs_example_invoice_2026a",
"created_at": "2026-09-02T09:15:04Z",
"expires_at": "2026-10-02T09:15:04Z",
"available": true
}
],
"retention_days": 30
}Returns up to 20 results, newest first. If next_cursor is returned, pass its value as ?before=NEXT_CURSOR to request the next page.
Illustrative responses. Authenticated results are saved for 30 days. Synchronous validation does not retain uploaded XML.
Pricing
Free each month, then pay as you go
Every account has these free allowances each month. With Pay as you go switched on, usage past them is charged at the rates below, within the monthly limit you set. Prices exclude VAT.
Validations
Each validation that reaches a valid or invalid result.
250 validations free each month
| Paid units after the free allowance | Rate per 1,000 |
|---|---|
| First 10,000 | £2.00 |
| Next 90,000 | £1.50 |
| Next 900,000 | £1.00 |
| Above 1,000,000 | £0.75 |
Generated invoices and credit notes
Each generated invoice or credit note that passes its own validation. The readable PDF is included.
100 generated documents free each month
| Paid units after the free allowance | Rate per 1,000 |
|---|---|
| First 10,000 | £4.00 |
| Next 90,000 | £3.00 |
| Next 900,000 | £2.00 |
| Above 1,000,000 | £1.50 |
Paid usage of Ironfang Finance needs an approved UK or EU business profile on the account. The free allowances are open to everyone, and the anonymous tools on this site need no account at all.
Operational limits
The same on every account. Paying more never lifts them.
- XML of up to 5 MiB
- Hybrid PDFs of up to 20 MiB
- Hybrid PDFs of up to 200 pages
- Up to 100 documents in one batch
Questions
Know what your result means.
- Do I need an account to try it?
- No. The free Peppol, XRechnung and ZUGFeRD / Factur-X validators accept a sample or your own document without an account. Create an account when you want saved validation history and API integration.
- When do I pay?
- Every account has a free monthly allowance of validations and another of generated invoices and credit notes, renewed on the first day of each UTC calendar month. No card is needed. Past an allowance, that work stops until the next month unless Pay as you go is switched on; then it is charged at the published rates, within the monthly usage limit you set. Paid usage of Ironfang Finance needs an approved UK or EU business profile. The anonymous browser tools stay free, with request and rate limits.
- Will I be charged if I reach my allowance?
- Only with Pay as you go switched on. Without it, new validations or generations stop when their allowance is used up and start again the next month. With it, usage past the allowance is charged, and work that would go past the account's monthly usage limit, or a limit set for Ironfang Finance, is refused before it starts. Prices exclude VAT, which is added on the invoice where it applies. Existing results stay available within their retention period.
- What happens to my invoice?
- Synchronous validation does not retain the uploaded document. Anonymous results are transient; authenticated result JSON and findings are retained for 30 days and can be deleted sooner. Durable API jobs, when enabled, temporarily retain encrypted input until completion, cancellation or 24-hour expiry cleanup.
- Can I download the result?
- Yes. The Peppol validator downloads JSON and an unsigned readable report you can print or save as a PDF from your browser. Through the API, any retained result can be issued as a signed report. 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.
Less to operate. More to ship.
Start with one document.
Try the sample, understand the findings and bring validation into your workflow.
No card is needed for a free account. Validate and generate within the free monthly allowances, and switch on Pay as you go when you need more.