SEF, Sistem elektronskih faktura, is the central electronic invoice system of the Serbian Ministry of Finance. Domestic e-invoices between businesses and with the public sector pass through it, under the Law on Electronic Invoicing. Invoices are UBL 2.1 files that follow a Serbian specification of the European standard EN 16931, and each has a status in SEF. Klarbon plans to open and check SEF invoices; this is not available yet.
What is in a SEF invoice?
| Property | Value |
|---|---|
| Syntax | UBL 2.1 Invoice and CreditNote |
| Specification identifier | urn:cen.eu:en16931:2017#compliant#urn:mfin.gov.rs:srbdt:2022 |
| With the extension | ...#conformant#urn:mfin.gov.rs:srbdtext:2022 |
| National rules | Serbian tax identifier (PIB), public funds user number (JBKJS), VAT categories and exemption reasons |
| Specification | version of 18 December 2025 |
| Owner | Ministry of Finance of the Republic of Serbia |
The Ministry's specification defines the CIUS, the optional extension and the identifiers (Ministry of Finance specification). The eFaktura site publishes the API specification, the internal technical manual, XML examples, a validation service and the laws and rulebooks (eFaktura, regulations).
What SEF adds beyond the file
| UBL file | SEF | |
|---|---|---|
| Holds | the invoice data | the invoice, its status and its history |
| Actions | none | send, accept, reject, cancel, storno |
| VAT | VAT on the invoice | electronic VAT records, individual and summary |
What does Klarbon do with SEF invoices?
Opening and checking SEF invoices against the Serbian rules is planned, not available yet. Klarbon does not connect to SEF. It opens UBL invoices that follow EN 16931; see the invoice viewer.
Related
Frequently asked questions
What is SEF?
Sistem elektronskih faktura, the electronic invoice system of the Serbian Ministry of Finance. Domestic e-invoices between businesses and with the public sector are exchanged through it, under the Law on Electronic Invoicing.
Which format does SEF use?
UBL 2.1 Invoice and CreditNote that follow the Serbian adaptation of EN 16931, identified as urn:cen.eu:en16931:2017#compliant#urn:mfin.gov.rs:srbdt:2022, with an optional Serbian extension.
Is a valid EN 16931 invoice enough for SEF?
No. SEF applies Serbian rules, tax identifiers and categories, and an invoice has a status in SEF that changes as it is sent, accepted, rejected or cancelled, which EN 16931 validity does not show.
Can software connect to SEF directly?
Yes. The Ministry publishes an application interface for direct access, with an API key, to send UBL files, fetch invoices, and accept or reject incoming ones.
Sources
- Ministry of Finance, SEF API documentation, 31 July 2026 (PDF, in Serbian) efaktura.gov.rs
- Ministry of Finance, eFaktura (in Serbian) efaktura.gov.rs
- Ministry of Finance, specification of the EN 16931-1 adaptation for domestic e-invoices in Serbia, 18 December 2025 (PDF, in Serbian) efaktura.gov.rs
- Ministry of Finance, electronic invoicing regulations efaktura.gov.rs