SAPI-SK: One Standard API for All Digital Access Points

Starting on 1 January 2027, electronic invoicing (eInvoice) will become mandatory for selected business transactions in Slovakia. Companies and ERP vendors will need to exchange electronic invoices through the Peppol network.

For software vendors, this raises an important question:

Should an ERP system integrate separately with every Peppol Access Point, or is there a common interface?

The answer is SAPI-SK (Standardised Access Point Interface – Slovakia), a standardized communication interface designed to simplify integration between ERP systems and certified Peppol Access Points.

What is SAPI-SK?

SAPI-SK is a standardized API specification that enables ERP systems to communicate with certified digital access point providers through a single interface.

Without such a standard, every provider could expose its own proprietary API, forcing ERP vendors to develop and maintain multiple integrations.

By implementing SAPI-SK once, an ERP system can communicate with different certified providers without changing its business logic.

How Does It Work?

ERP System
      │
      │  SAPI-SK
      ▼
Digital Access Point
      │
      ▼
 Peppol Network
      │
      ▼
Business Partner

The ERP system communicates only through the SAPI-SK interface.

The certified Access Point is responsible for:

• validating electronic invoices,
• communicating with the Peppol network,
• delivering invoices to recipients,
• complying with Slovak and European eInvoicing regulations.

Why Is a Standard Important?

Implementing a common interface provides significant advantages for ERP vendors and their customers:

• one integration instead of many,
• easier replacement of Access Point providers,
• lower development and maintenance costs,
• simplified compliance with future legislative changes,
• long-term interoperability.

Instead of building provider-specific integrations, software vendors can focus on business functionality while relying on a standardized communication layer.

Public Technical Specification

One of the strengths of the SAPI-SK initiative is the availability of public technical documentation.

Developers can access:

• OpenAPI 3.0 specification,
• Swagger documentation,
• authentication endpoints,
• document submission endpoints,
• document retrieval endpoints,
• communication workflows between ERP systems and certified Access Points.

This significantly reduces the complexity of implementing electronic invoicing support.

Our Approach at 4B Software

At 4B Software, we are preparing our ERP solutions for electronic invoicing with a strong focus on flexibility and long-term sustainability.

Our implementation strategy is based on three principles:

• compliance with the SAPI-SK standard,
• independence from any specific Access Point provider,
• a modular integration layer that allows providers to be changed with minimal effort.

This architecture ensures that our customers remain flexible as the electronic invoicing ecosystem continues to evolve.

Looking Ahead

Electronic invoicing represents one of the most significant changes in business software in recent years.

SAPI-SK provides a standardized foundation that simplifies communication between ERP systems and certified Peppol Access Points while reducing implementation complexity for software vendors.

At 4B Software, we continue to monitor legislative and technical developments to ensure our solutions remain fully compliant and ready for the future of electronic invoicing in Slovakia.