◆ ePošťák API

How do you want to connect your ERP?

A few simple ways to connect an application or ERP to the Peppol network. Choose what your software can produce.

What can your software produce?

Your choice: Connector

Connector accepts business JSON and manages the standard ERP workflow through delivery, receiving, and business responses.

Why Connector

  • 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

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.

Connector · business JSONillustrative
POST /api/v1/connector/documents
Idempotency-Key: invoice-2026-0042

{
  "customerRef": "erp-vzor",
  "externalId": "invoice-2026-0042",
  "delivery": "send",
  "type": "invoice",
  "number": "2026-0042",
  "issueDate": "2026-07-15",
  "dueDate": "2026-07-29",
  "currency": "EUR",
  "buyerReference": "ODD-IT",
  "recipient": { "country": "SK", "taxId": "2120123456" },
  "lines": [{
    "description": "Mesačná licencia",
    "quantity": 1,
    "unit": "C62",
    "unitPrice": 100,
    "vatRate": 23,
    "taxTreatment": "standard"
  }]
}

Connector is free to try in a sandbox with two test companies.

Request a sandboxOpen Connector documentation

Who are you connecting and who pays?

Who pays for the API
Your company — by usage

The owner or an admin orders the API in Settings → API and integrations and creates a key right away.

Open API settings
Your decision

Connector · I am connecting my own company

Who pays: Your company — by usage.

  1. Order the API in Settings and create an sk_live_* key.
  2. Connect your ERP using the Connector documentation.
  3. Pay only for sent and received documents.
Open API settings
REST API free for testing

Three interfaces. One price.

The sandbox is free. In production you pay only for sent and received documents — no monthly fee and no setup fee.

Full API pricing
BandSendReceive
Band 01
1 – 1 000 docs/mo.
Send0.10 €
Receive0.08 €
Band 02
1 001 – 2 000 docs/mo.
Send0.08 €
Receive0.07 €
Band 03
2 001 – 5 000 docs/mo.
Send0.06 €
Receive0.06 €
Band 04
5 001 – 20 000 docs/mo.
Send0.05 €
Receive0.05 €
Band 05
20 001+ docs/mo.
Send0.04 €
Receive0.04 €

Kaja Solutions is not VAT registered yet, so the listed amounts are final. The application for VAT registration has been filed.

Enterprise add-on — AMQPS/RabbitMQ, Kafka or Edge Connector. An optional Enterprise API extension for AMQPS queues in RabbitMQ, Kafka topics, or a hybrid or on-premise Edge Connector. Implementation, operations, and licence are priced individually based on scope.

How to start

From sandbox request to production

First test the integration safely on the Peppol test network. The agreement and billing come afterwards.

  1. Request a sandbox

    Send us the access email. Company, API and purpose are optional.

  2. Get free sandbox access

    An operator creates the account and two test companies. The sandbox is separate from production and creates no commitment.

  3. Test the full flow and choose an API

    Verify sending, receiving and statuses on the Peppol test network. Choose Connector, SAPI, or Enterprise API.

  4. Request production access

    Choose whether the integrator or the individual companies pay. We review the request, agreement and permissions.

Request a sandboxOpen production activationThe full onboarding guide

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.

◆ Practical questions

What integrators ask most often

Can an ERP automate invitation creation and track its status?

Yes. Enterprise Core API lets an ERP create an invitation for a specific company and track its status using existing partner access. The SAPI standard remains unchanged. An authorized company representative must explicitly accept. Accepted consent does not yet confirm activation and billing are complete. Store the one-time link securely; do not retry invitation creation blindly after an uncertain response. The API documentation provides the workflow and examples under Client onboarding — ERP automation.

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.

Start with a sandbox request

An access email is enough. ePošťák verifies you and an operator manually creates access with two test companies.

info@epostak.skRequest production access
Technical resourcesAPI documentationSDKs in 6 languagesEnterprise Core OpenAPIEnterprise Full OpenAPIERP Test LabeInvoice validatorE-invoice visualizationPricing

The 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.