API Integration of the Digital Mailbox for ERP and Integrators
·Voluntary e-invoicing 2026 · Mandatory from January 1, 2027
ePošťák is the first certified Slovak digital mailbox with a public REST API. Use the free sandbox and the SAPI/Enterprise API to send e-invoices via Peppol BIS 3.0 to 39 countries — from €0.06 per delivered document.
API integration of the digital mailbox for connecting ERP, accounting software, and custom solutions to the Peppol network. Invoicing automation via SAPI Standard(Financial Administration of the Slovak Republic), Enterprise APIwith 40+ endpoints, webhooks, OCR, multi-company. Documentation in Slovak and English.
SDK in 6 languages • Sandbox within 24h for free
Platform
Choose Your Interface
Two APIs, one certified digital mailbox. Choose according to your needs.
What's Included
Why Enterprise API Is Worth It
Pay-per-success pricing from €0.06 per document does not mean "cheap API." Every price includes full operational responsibility.
SLA 99.5%
Guaranteed API availability. Status page with realtime uptime, compensation for SLA breaches.
24/7 Support
Email, phone, Slack channel. Average first response under 15 minutes. Direct contact with the engineering team.
OCR Extraction from PDF
AI parsing of scanned invoices into structured data. Includes a bulk endpoint — included in the price, not as an addon.
Daily Backups + Archive
All UBL, PDF, and MLS artifacts are archived for 10+ years (legal requirement). Daily encrypted backups off-site.
Integration Process
From Sandbox to Production
Three steps to integrate e-invoicing through a certified digital mailbox.
Get Your Sandbox
Write to info@epostak.sk. API keys and OAuth credentials within 24 hours for free.
Integrate
Enterprise SDK in 6 languages, complete documentation in SK + EN, technical support.
Launch Production
From €0.06/doc, no fixed fee. White-label — your clients do not pay for the mailbox.
Endpoints
What the API Integration of the Digital Mailbox Covers
Current status as of May 2026. Sandbox and all endpoints are available today — ready for mandatory e-invoicing from January 1, 2027.
Documents
Sending and receiving e-invoices via Peppol, status tracking, AS4 confirmations.
POST /send GET /inbox GET /status
Validation & Conversion
UBL validation against Peppol BIS 3.0, JSON↔XML conversion, preflight check.
POST /validate /convert /preflight
AI Extraction
Extraction of invoice data from PDF and images. Individually or in bulk (50 files).
POST /extract /extract/batch
Webhooks
Real-time notifications, HTTPS validation, delivery history, filtering.
CRUD /webhooks GET /deliveries
Company Management
Multi-company access, assignment by company ID, Peppol ID registration, bulk.
GET /firms POST /assign /batch
Peppol Network
SMP lookup, Peppol Directory (3.6M+ records), company ID verification.
GET /participants /directory
SDK
SDK in 6 Languages
Install and integrate e-invoicing in minutes.
Code Examples
API Integration Examples — cURL, Python, Node.js
Updated May 2026. A real POST /api/v1/invoices request and a webhook payload example for the document.delivered event. Full reference in SAPI documentation or Enterprise API documentation.
curl -X POST https://epostak.sk/api/v1/invoices \
-H "Authorization: Bearer sk_live_..." \
-H "Content-Type: application/json" \
-d '{
"recipientId": "0245:2020298610",
"documentType": "invoice",
"ublXml": "<?xml version=\"1.0\"?>..."
}'Comparison
SAPI vs Enterprise API
Two interfaces for API integration of the digital mailbox. SAPI is the standardized interface of the Financial Administration of the Slovak Republic; Enterprise API is our own extended interface for integrators.
| Feature | SAPI Standard | Enterprise API |
|---|---|---|
| Authentication | OAuth 2.0 | API key (Bearer) |
| Number of endpoints | 8 (core) | 40+ (extended) |
| Webhooks | — | ✓ (HMAC SHA-512) |
| OCR from PDF | — | ✓ (AI extraction) |
| UBL ↔ PDF conversion | — | ✓ |
| Multi-company (white-label) | — | ✓ (unlimited) |
| Bulk operations | — | ✓ (up to 500/request) |
| SDK | TS, Python, PHP, C#, Java, Ruby | TS, Python, PHP, C#, Java, Ruby |
| SLA | 99.5% | 99.5% |
| Price | from €0.06/doc | from €0.06/doc |
| Best for | software with SAPI implementation | ERP, integrators, white-label |
Full reference: SAPI documentation · Enterprise API documentation
Current
Current as of May 2026
Latest milestones of the API integration for the digital mailbox. We follow the Peppol roadmap and the regulatory calendar of the Financial Administration of the Slovak Republic.
May 2026
SDK Complete in 6 Languages
TypeScript, Python, PHP, C#/.NET, Java, and Ruby — all on GitHub as open-source. Java SDK GA.
April 2026
Peppol Testbed: 10/10 Passed
All 10 SK Peppol test scenarios (billing and self-billing) passed. Ready for production.
March 2026
OpenPeppol Member
ePošťák is a certified Peppol Access Point and member of OpenPeppol. We deliver to 39 countries.
Find the complete timeline and deployment plan in the roadmap. For context on why ePošťák exists and who is behind it, see certified digital mailbox.
Pricing
Transparent Pricing Without Hidden Fees
Valid for voluntary e-invoicing in 2026 and mandatory e-invoicing from January 1, 2027. The integrator pays for all companies — client companies pay nothing for the digital mailbox. Volume is calculated across all managed companies.
2026 Promotion
You only pay for actually delivered invoices. If you send an invoice via API and the recipient is not yet on the Peppol network, you pay nothing — we bill only after successful delivery.
Sandbox
Free
Full API access in the test environment with no commitment
Sent
| Volume | Price/doc |
|---|---|
| 1 – 1 000 | 0,10 € |
| 1 001 – 2 000 | 0,08 € |
| 2 001+ | 0,06 € |
| 5 000+ | Custom |
Received via API
| Volume | Price/doc |
|---|---|
| 1 – 1 000 | 0,08 € |
| 1 001 – 2 000 | 0,07 € |
| 2 001+ | 0,06 € |
| 5 000+ | Custom |
Volume across companies — volume discounts are calculated across all managed companies, not per company. If you manage 20 companies and each sends 100 documents per month, the total volume is 2,000 documents.
For Whom
Who Is the API Integration for?
Integrators and ERP providers who need to connect their accounting software to the Peppol network — or automate invoicing for their companies and clients.
ERP Systems
Automatic sending and receiving of e-invoices directly from your ERP via Peppol.
Billing Software
Add Peppol to your application. White-label — your clients see your brand.
Accounting Platforms
Multi-company API access. Manage dozens of companies from a single account.
Custom Applications
REST API with documentation in SK + EN. Build your own solution.
Frequently Asked Questions
SAPI (Standard API for Integration) is a voluntary standardized interface designed by the working group at the Financial Administration of the Slovak Republic for unified e-invoicing integration. Implementation is not mandatory — certified mailbox providers choose whether to offer it. ePošťák was the first mailbox to fully implement and make SAPI available to developers. Thanks to this, you write the integration once and connect to any SAPI-compatible provider. Documentation in Slovak and English.
SAPI is a standardized interface with OAuth 2.0 authentication, defined by the Financial Administration of the Slovak Republic — suitable for companies and software that want to simply send and receive e-invoices via API. Enterprise API is our own interface with API key, webhooks, bulk operations, AI extraction from PDF, UBL→PDF conversion, and white-label support — 40+ endpoints for integrators managing multiple companies and ERP software with more demanding requirements.
The sandbox for testing is free. During 2026, you only pay for actually delivered invoices — if you send an invoice via API and the recipient is not yet on the Peppol network, you pay nothing. In production, you pay according to volume pricing from €0.06 per document at higher volumes. No fixed monthly fee.
Contact us at info@epostak.sk or through the contact form. We will create a sandbox environment with full API access within 24 hours. Test API keys and OAuth credentials are provided immediately.
Yes. ePošťák is a certified Peppol Access Point and member of OpenPeppol since March 2026. Through the API, we support Peppol BIS 3.0, AS4 protocol, SMP lookup, and sending e-invoices to 39 countries.
Yes. Enterprise API supports multi-company access — from one integration account, you manage an unlimited number of companies. Your clients do not pay for the digital mailbox.
Official SDKs are available in 6 languages: TypeScript/JavaScript, Python, PHP, C#/.NET, Java, and Ruby. All are open-source on GitHub.
ePošťák was the first digital mailbox in Slovakia to offer a complete REST API for e-invoicing integration. While other certified providers offer only a web interface, ePošťák enables full automation via SAPI and its own Enterprise API with 40+ endpoints.
first certified digital mailbox with API
Integrate e-invoicing into your software today
Free sandbox, SDK in 6 languages, documentation in SK + EN, technical support.