Services / SEF e-invoicing
SEF e-invoicing integration for companies operating in Serbia
Serbian e-invoicing integration for companies that create invoices in their own software and then retype them into SEF, the government e-invoicing system, or upload them by hand. The service I built for the BKC Soft point of sale software has sent more than 10,000 invoices straight from the software since 2023, the first year e-invoicing was mandatory between businesses.
- invoices sent through the service
- 10,000+
- routes (types of request) in the service
- 50+
- running, updated with every law change
- since 2023
What Serbian e-invoicing integration includes
Invoices sent from your own software
An outgoing invoice goes to SEF from the program it was created in, and into the Central Invoice Register where that applies. Nobody retypes it in a browser.
Incoming invoices
Incoming invoices are downloaded as XML and PDF and accepted or rejected from your software.
Status tracking
Your software always knows whether a sent invoice was delivered, accepted or rejected.
VAT records
The BKC Soft service also files individual electronic VAT records, which the law requires alongside e-invoices.
Checks before sending
The XML (the format SEF accepts) is validated before sending, so errors are fixed while the invoice can still be changed.
A test environment
Almost every route has a test version that sends to the demo SEF, so the full flow is tried before a real invoice goes out.
E-delivery notes in the same service
The same service sends and receives Serbian electronic delivery notes, so your software needs nothing else.
Law changes handled
I follow every amendment as it is published, build it into the service and test it on the demo environment. The changes that apply from January 1, 2027, are already in.
Who this is for, and who it is not for
A good fit if
- your company or Serbian subsidiary issues invoices in its own software and someone then enters them into SEF by hand.
- you make software used by several companies. At BKC Soft, when the government changes the specification, users receive one new file and the software stays the same.
- you send both e-invoices and e-delivery notes and want both handled in one place.
Not a fit if
- you send a few invoices a month. Entering them directly in SEF through a browser is simpler.
- your software cannot be extended to send and receive requests through an API (an address programs use to exchange data). Then the e-invoicing portal I am preparing is the better option.
- you need the connection within days. An integration takes 20 days or more.
How I work
- 01
About your software
Tell me the name of the software, how it creates invoices and who maintains it. Messages sent before 5 pm CET get a same day reply.
- 02
Specification
We agree which messages it sends and receives: invoices, statuses, incoming invoices, VAT records, delivery notes.
- 03
An API for your software
I build an API your software calls, or connect the software directly if it allows that.
- 04
Test on the demo SEF
The whole flow runs through the Ministry of Finance demo environment before a single real invoice is sent.
- 05
Go live
You enter the API key, generated in SEF, and the software starts sending real invoices.
- 06
Law changes
When the rules change, I update the service, test it on the demo environment, and the change is ready for production.
Who must use SEF, and since when
SEF is the Serbian Ministry of Finance's electronic invoicing system, governed by the Law on Electronic Invoicing, amended six times since 2021, most recently in August 2026. Under the law, the private sector means every VAT payer; businesses outside the VAT system can register as voluntary users. That includes Serbian subsidiaries of foreign companies registered for VAT.
| Obligation | Applies from |
|---|---|
| public sector receives and stores e-invoices and issues them to other public bodies | May 1, 2022 |
| private sector issues e-invoices to the public sector | May 1, 2022 |
| public sector issues e-invoices to the private sector | July 1, 2022 |
| private sector receives and stores e-invoices | July 1, 2022 |
| e-invoices between private sector companies | January 1, 2023 |
| amendments in Official Gazette no. 80/2026 | January 1, 2027; purchases from farmers and export customs declarations from July 1, 2027 |
A private sector e-invoice must be kept for 10 years from the end of the year it was issued, in SEF or with an information intermediary. For what applies to your company specifically, ask your accountant; my job is making sure the software does it correctly.
A real example: the efakture.exe service for BKC Soft
BKC Soft makes point of sale software accredited with the Serbian Tax Administration under registration number 88. It has run in shops and cafés for years, and it was written to talk to a local database and a fiscal printer, not to a government system that wants UBL XML (the prescribed invoice format), an API key and an encrypted connection. Rewriting it was not an option.
So everything that leaves the venue was moved into a separate service written in Go: one executable file, no installation. The software calls the service on the same computer and gets an answer; it knows nothing about XML or keys. The service sends invoices to SEF, downloads incoming ones, tracks statuses, files VAT records and sends e-delivery notes, and it also carries email and daily reports.
The service has run since 2023. It now has more than 50 routes and has sent more than 10,000 invoices. The full story is in the efakture.exe case study. When the government changes the specification, users receive one new file and the point of sale software stays untouched.
10,000+
invoices sent
50+
routes, with test versions
1
file per update, no reinstall
Technology and why
SEF accepts invoices in UBL 2.1 (an international XML standard for invoices), through an API authenticated with a key the company generates in SEF. The Ministry of Finance runs a separate demo environment for testing and last updated its API documentation on July 31, 2026.
The BKC Soft service is written in Go because it compiles to a single executable with no dependencies: it is copied onto the venue computer and started. For software that runs on a server or in a browser, I build the API in PHP or Laravel, depending on what your software already uses. The BKC Soft service is theirs for now, but it can be adapted for other companies.
SEF integration pricing and timelines
Connecting your software to SEF is quoted per project and starts at around 300 EUR, depending on what the software needs to send and receive. If you need a website that sends e-invoices itself, a complete site starts at 350 EUR.
An integration takes 20 days or more, mostly depending on how quickly I get documentation and answers about your software. The e-invoicing portal I am preparing will have a free 3 month trial, followed by a monthly subscription.
SEF e-invoicing questions
What do I need to connect my software to SEF?
Software that can be extended to send and receive requests through an API I build, and an API key, which you generate in SEF. Accounting software works too; send me its name and who maintains it, and I check before I quote.
How long does an integration take?
Twenty days or more. It depends mostly on how quickly I receive documentation about your software and answers to my questions.
What happens when the rules change?
I follow amendments as they are published, build them into the service and test them on the demo environment. The amendments from Official Gazette no. 80/2026, which apply from January 1, 2027, are already in.
Can I use the service you built for BKC Soft?
Right now only BKC Soft uses it. It can be adapted for other companies; tell me which software you use and what it needs to send.
We do not have our own software. What then?
For delivery notes, the e-delivery notes portal already works, and an e-invoicing portal is in preparation. You will only enter your API key, and the first 3 months will be free.
Sources (checked October 4, 2026)
- Electronic Invoicing System, efaktura.gov.rs: official site, legal basis and system access.
- Law on Electronic Invoicing, consolidated text (Official Gazette nos. 44/2021 to 80/2026), Articles 2, 15 and 24.
- Amendments, Official Gazette no. 80/2026, Ministry of Finance notice of September 1, 2026.
- SEF API specification, documentation updated July 31, 2026.
Tell me which software you use
Send the name of your software, who maintains it and what it needs to send to SEF. Messages sent before 5 pm CET get a same day reply with an assessment of whether and how it can be connected.