📖 Guide8 min read
Best E-Invoicing APIs for ERP & CRM Integration in 2026
A developer's guide to the best REST APIs for generating XRechnung, FatturaPA, ZUGFeRD, and Peppol invoices programmatically — with code examples and integration patterns.
By EU E-Invoicing Hub
If you are building an ERP, CRM, or e-commerce platform that needs to generate compliant EU e-invoices, you need a reliable API. Here is our assessment of the best options available in 2026.
What to Look For in an E-Invoicing API
- Format coverage: Does it support all formats you need? (XRechnung, ZUGFeRD, FatturaPA, Peppol BIS)
- Validation before delivery: Does it validate against EN 16931 before sending?
- Webhook support: For SDI/Peppol status updates without polling
- Multi-country: If you invoice across borders, you need one API for all EU formats
- Rate limits: Check limits for bulk invoice generation
Top APIs Compared
easybill API (Germany-focused)
- Base URL: api.easybill.de
- Authentication: Bearer token
- Format support: XRechnung (UBL + CII), ZUGFeRD 2.3, Peppol BIS
- Rate limit: 300 req/5 min on Plus plan
- Webhook: Yes (Peppol delivery status)
POST /rest/v1/documents
{
"type": "INVOICE",
"customer_id": 12345,
"document_date": "2026-04-01",
"items": [{"description": "Consulting", "unit_price": 1500.00, "vat_percent": 19}]
}
Billomat API (Germany, API-first)
- Similar coverage, slightly lower rate limits
- Strong recurring invoice and subscription management endpoints
- Zapier / Make.com native integrations
Fattura24 API (Italy)
- FatturaPA generation and SDI submission
- SDI delivery status webhooks
- WooCommerce and Shopify native plugins available
Integration Patterns
Pattern 1: Trigger on payment — Generate invoice when payment confirmed (e-commerce) Pattern 2: Trigger on order — Generate and send on B2B order (ERP) Pattern 3: Batch generation — End-of-day bulk creation for high-volume retailers
apidevelopererpcrmintegration2026restwebhook
