Choose one API. Not three layers.
How do you want to connect your ERP?
Connector, SAPI, and Enterprise API are not three layers you must implement together. Choose one interface based on what your ERP already sends and how many technical steps you want to control.
Digital mailbox API and e-invoice API in one integration
A digital mailbox API lets an ERP send, receive, and track e-invoices over the Peppol network. An e-invoice API serves the same practical goal: it connects accounting or invoicing software to a certified delivery service without manually re-entering document data.
A simple rule: if the ERP submits invoice data as JSON, start with Connector. If it already produces ready UBL 2.1 and needs a portable standard, choose SAPI. Use Enterprise API when you need to control individual technical steps.
Your choice: Connector
Connector
Connector accepts business JSON and manages the standard ERP workflow through delivery, receiving, and business responses.
- What you send
- Business JSON containing document data. ePošťák creates the standard document and hides the Peppol mechanics.
- Who can pay
- An end company can order and pay for its own Connector, or a managed integrator can pay for authorized companies on a consolidated basis. Technical delegation with per-company billing is available through SAPI or Enterprise API.
- The recommended path for new ERP business JSON
- customerRef without X-Firm-Id and ordinary recipient IDs
- Managed send, stage, receiving, status, and business responses
- Existing SAPI and Enterprise API integrations remain supported
ConnectorOne connection. We handle the complexity.
Updated: July 19, 2026
Connector takes over the complex part of integration
Without Connector
With Connector
ConnectorOne integration point. ePošťák handles the rest of the workflow.
How to start
From sandbox request to production
The sandbox is free for every approved applicant. First test the integration safely on the Peppol test network; contracts, billing, and production access come afterwards.
- 1
Request a sandbox
Email us from your work address with your company name, requested API, and a short integration purpose. We manually verify and approve the request.
- 2
Get free sandbox access
An operator creates the integrator account, test companies, and required access. The sandbox is separate from production and creates no paid commitment.
- 3
Test the full flow and choose an API
Verify sending, receiving, statuses, and company handling on the Peppol test network. During testing, choose Connector, SAPI, or Enterprise API.
- 4
Request production access
After completing the sandbox, choose on the activation page whether the integrator or individual companies pay. We then review the request, agreement, and production permissions.
Practical questions
What integrators ask most often
These answers reflect recurring customer questions and the current public interface contract.
Which integration interface should I choose?
Connector is the recommended managed route when an ERP submits business JSON. Choose SAPI if you already create ready-made UBL 2.1 and need the portable Slovak Financial Administration standard. Enterprise API is for integrations that need step-level control, webhooks, preflight, bulk operations, or multi-company management.
What is the difference between Connector, SAPI, and Enterprise API?
Connector turns business JSON into a standard document and manages the usual send, stage, inbox, status, and business-response flow. SAPI transports ready-made UBL 2.1 in its standard envelope and does not create an invoice from business JSON. Enterprise API exposes advanced steps, events, batch operations, and multi-company permissions directly to the integrator.
How do I get sandbox access?
Email info@epostak.sk from your work address and include the company name and integration purpose. ePošťák verifies the partner and an operator manually creates sandbox access, test companies, and web inboxes where needed. The sandbox is free and does not start a production commitment. Production is activated separately after the go-live review, signature of the selected partner-mode agreement, and Kaja Solutions' countersignature.
Which formats can I send through the API?
Connector accepts business JSON, SAPI transports ready-made UBL 2.1, and Enterprise API accepts structured JSON or ready-made UBL XML depending on the operation. A PDF alone is not an e-invoice; Enterprise tools may use it as an extraction source, but the resulting structured document must still be reviewed and validated.
Does the API cover sending, receiving, and delivery status?
Yes. Connector and Enterprise API cover sending, inbox, events, and document status; SAPI provides its standard sending and receiving operations. Request acceptance or validation is not yet proof of delivery. The integration should follow the subsequent transport status or event.
What happens if the recipient is not on Peppol or does not support the document?
Recipient capability checks and preflight report whether delivery is possible and distinguish a missing Peppol ID, unsupported document type, or temporary lookup failure. If the recipient does not support the required document, ePošťák does not present it as delivered.
Can one integration manage multiple companies?
Yes. A technical partner and a managed integrator can use one central sk_int_* with SAPI, Enterprise API, and Connector for companies that granted specific revocable consent. Under technical delegation, each company pays under its own API order; in managed mode, the integrator pays on a consolidated basis. Access is always bound to a company and approved scopes; the partner never receives a firm's sk_live_* secret.
Who orders and pays for the API service?
There are three modes. A direct customer signs and pays directly and uses sk_live_*. A technical partner signs a no-fee partner authorization and uses a central sk_int_*, while every end company separately signs its own API order, pays Kaja Solutions for its own usage, and grants revocable consent. In managed mode, the integrator signs the Integrator Agreement and pays on a consolidated basis. The sandbox is free; production use has been billed since June 1, 2026 under the price list and actual document volume.
Does the ePošťák API support invoice attachments?
Yes. Enterprise API supports up to 20 attachments, 10 MB per file, and 15 MB in total after decoding. An attachment such as a PDF or delivery note supplements the structured invoice but does not replace the UBL document.
Which programming languages have SDKs?
SDKs are available for TypeScript/JavaScript, Python, PHP, C#/.NET, Java, and Ruby. The TypeScript package is published as @epostak/sdk; for the other languages, verify the current version and endpoint coverage in the SDK repository before deployment.
If you already have your own integration architecture
Start with a sandbox request
Request sandbox by emailePošťák verifies you and an operator manually creates access.
Request production accessThe commercial mode is independent of the payload format. With firm-scoped sk_live_*, the end company signs and pays. With a technical sk_int_*, the software vendor signs the Technical Partner Agreement, while every company separately signs its own API order, pays Kaja Solutions for its own usage, and grants revocable consent. With managed sk_int_*, the integrator signs the Integrator Agreement and pays on a consolidated basis. Integrator Agreement · Terms / DPA · Pricing