First certified digital mailbox with a complete API

API Integration of the Digital Mailbox for ERP and Integrators

Updated: May 13, 2026Voluntary 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 API with 40+ endpoints, webhooks, OCR, multi-company. Documentation in Slovak and English.

SAPI Enterprise API Connector ERP Test Lab XML validator

SDKs in 6 languages • OpenAPI 3.1 • self-service sandbox at dev.epostak.sk/integrator • production after go-live

TypeScriptPythoncURL

POST /api/v1/documents/send

const token = "eyJhbGciOiJSUzI1NiIs..."

// Sending an e-invoice via Peppol
const response = await fetch("https://epostak.sk/api/v1/documents/send", {
  method: "POST",
  headers: { Authorization: `Bearer ${token}`, "Content-Type": "application/json" },
  body: JSON.stringify({
    receiverPeppolId: "0245:0000000001",
    invoiceNumber: "FAK-2026-001",
    items: [{ description: "Vývoj softvéru", quantity: 8, unitPrice: 125, vatRate: 23 }],
  })
})

console.log(await response.json())

01Platform

Choose Your Interface

SAPI Standard, the full Enterprise API, and Connector as the shortest ERP path into the Peppol network through ePošťák.

FS SR Standard8 endpointov

SAPI Standard

A standardized interface defined by the Financial Administration of the Slovak Republic. OAuth 2.0 authentication, 8 endpoints for sending and receiving e-invoices.

For whom: companies and software that want to easily send and receive e-invoices via API. Implement once, connect to any SAPI-compatible mailbox provider.

Unified standard across providers
OAuth 2.0 + 8 core endpoints
Documentation SK + EN
Platform SLA 99.5%

SAPI

Our API40+ endpoints

Enterprise API

Our own REST API with OAuth 2.0 JWT authentication, webhooks, bulk operations, OCR extraction from PDF, and white-label support.

For whom: integrators managing dozens of companies and ERP software with more demanding requirements — OCR from PDF, webhooks, bulk operations, Platform SLA 99.5%, and multi-company account.

Platform SLA 99.5% + 24/7 support
OCR from PDF, webhooks, bulk operations
White-label multi-company + daily backups

Enterprise API

Fast path1 day

ePošťák Connector

A simple product entry point on top of the Enterprise API. ERP teams do not have to compose Peppol validation, sending, outbox for stage now, send later, status, inbox, and evidence from many endpoints.

For whom: ERP and accounting software vendors that want to connect customers to the Peppol network quickly. When ePošťák is selected as the delivery-service provider, Connector gives them a simple route instead of a complex integration.

Typical test connection of an ERP system to the Peppol network in one day
No required webhooks; status and inbox work through simple polling
Same keys, documentId, evidence, and transition to Enterprise API

Connector

02What'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.

0199.5

Platform SLA 99.5%

Availability of our API platform under the GTC. The status page separates the ePošťák platform from the Peppol network and external delivery.

0224/7

24/7 Support

Email, phone, Slack channel. Average first response under 15 minutes. Direct contact with the engineering team.

03AI

OCR Extraction from PDF

AI parsing of scanned invoices into structured data. Includes a bulk endpoint — built into the price, not a paid add-on.

0410y+

Daily Backups + Archive

UBL, PDF, and transport evidence are available according to the selected plan and the retention rules in the GTC. Daily encrypted backups off-site.

03Integration Process

From Sandbox to Production

Three steps to integrate e-invoicing through a certified digital mailbox.

Get Your Sandbox

Register at dev.epostak.sk/integrator. After email verification and sandbox integrator approval, create test API keys and sandbox firms. Production integrator access is separate and opens only after approved go-live and a signed contract.

Sandbox login

Integrate

SDKs in 6 languages: TypeScript on npm, Python/PHP/.NET/Java/Ruby as source on GitHub.

SAPI docs Enterprise docs

Launch Production

From €0.06/doc, no fixed fee. White-label — your clients do not pay for the mailbox.

Pricing

04Endpoints

What the Digital Mailbox API Integration 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 /api/v1/documents/send
GET /api/v1/documents/inbox
GET /api/v1/documents/{id}/status

Validation & Conversion

UBL validation against Peppol BIS 3.0, JSON↔XML conversion, preflight check.

POST /api/v1/documents/validate
POST /api/v1/documents/convert
POST /api/v1/documents/preflight

AI Extraction

Extraction of invoice data from PDF and images. Individually or in bulk (50 files).

POST /api/v1/extract
POST /api/v1/extract/batch

Webhooks

Real-time notifications, HTTPS validation, delivery history, filtering.

POST /api/v1/webhooks
GET /api/v1/webhooks/{id}/deliveries
POST /api/v1/webhooks/{id}/test

Company Management

Multi-company access, assignment by company ID, Peppol ID registration, bulk.

GET /api/v1/firms
POST /api/v1/firms/assign
POST /api/v1/firms/assign/batch

Peppol Network

SMP lookup, Peppol Directory (3.6M+ records), company ID verification.

GET /api/v1/peppol/participants/resolve
POST /api/v1/peppol/participants/batch
GET /api/v1/peppol/directory/search

05SDK

SDKs in 6 Languages

The TypeScript SDK is published on npm. Python, PHP, .NET, Java, and Ruby SDKs are available as source on GitHub.

staniduris/epostak-sdk

01TypeScript / JavaScriptnpm i @epostak/sdk

02PythonSource on GitHub

03PHPSource on GitHub

04C# / .NETSource on GitHub

05JavaSource on GitHub

06RubySource on GitHub

06Code Examples

API Integration Examples — cURL, Python, Node.js

Updated May 2026. A real POST /api/v1/documents/send 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/documents/send \
  -H "Authorization: Bearer eyJhbGciOiJSUzI1NiIs..." \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: inv-2026-001" \
  -d '{
    "receiverPeppolId": "0245:0000000001",
    "invoiceNumber": "FAK-2026-001",
    "currency": "EUR",
    "items": [
      {"description": "Vývoj softvéru", "quantity": 8, "unitPrice": 125, "vatRate": 23}
    ]
  }'

07Comparison

SAPI vs Enterprise API vs Connector

SAPI is the standardized interface of the Financial Administration of the Slovak Republic. Enterprise API is the full ePošťák technical surface. Connector is a simple managed flow on top of Enterprise API for fast ERP integration.

Feature	SAPI Standard	Enterprise API	Connector
01Authentication	OAuth 2.0	API key exchanged for JWT via /api/v1/auth/token	Same Enterprise API credentials
02Number of endpoints	8 (core)	40+ (extended)	Short managed flow for send, outbox for stage now/send later, status, inbox, events, and ack
03Webhooks	—	✓ (HMAC SHA-512)	Optional; polling works without webhook setup
04OCR from PDF	—	✓ (AI extraction)	Via Enterprise API when the integrator needs it
05UBL ↔ PDF conversion	—	✓	Via the same documentId in Enterprise API
06Multi-company (white-label)	—	✓ (unlimited)	Uses the same integrator permissions
07Bulk operations	—	✓ (up to 500/request)	Optimized for the most common ERP flow and full invoice lifecycle
08Client libraries	OpenAPI + HTTP examples	6 SDKs: npm + GitHub source	Connector namespace in SDK including outbox + HTTP examples
09SLA	platform 99.5%	platform 99.5%	Same infrastructure and platform SLA as Enterprise API
10Price	from €0.06/doc	from €0.06/doc	Same volume model, less integration work
11Best for	software with SAPI implementation	ERP, integrators, white-label	ERP teams that want a fast test connection to the Peppol network

Full reference:SAPI documentation Enterprise API documentation Connector for integrators

08Current

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 202601

SDKs in 6 Languages and OpenAPI Updated

The public docs now use the current /api/v1/documents/send and /api/v1/documents/* endpoints, JWT authentication, and distinguish the npm-published TypeScript SDK from GitHub-source SDKs for Python/PHP/.NET/Java/Ruby.

April 202602

Peppol Testbed: 10/10 Passed

All 10 SK Peppol test scenarios (billing and self-billing) passed. Ready for production.

March 202603

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.

09Pricing

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.

Sandbox

Free

Full API access in the test environment with no commitment

Sandbox login

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.

10For 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.

11FAQ

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 where you exchange an API key for a short-lived JWT via /api/v1/auth/token. It adds 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 is free. Production API/integrator usage is billed from June 1, 2026 based on documents actually sent and received.

Open https://dev.epostak.sk/integrator, enter your work email, verify it, and wait for sandbox integrator approval. In the sandbox integrator panel you can then create test API keys and sandbox firms for test SMP. The production integrator at https://epostak.sk/integrator is for approved go-live after a signed contract.

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.

SDKs are available in 6 languages: TypeScript/JavaScript, Python, PHP, C#/.NET, Java, and Ruby. The TypeScript SDK is published on npm as @epostak/sdk; the other SDKs are available as source on GitHub.

ePošťák was the first digital mailbox provider 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, SDKs in 6 languages, documentation in SK + EN, technical support.

Sandbox login View Documentation