Serbia: SEF Update 4.2.0 Reaches the Demo Environment and the Internal Technical Instruction Is Reissued on 1 October 2026

KGT Country Update | 2 October 2026 | VAT, e-invoicing and SAF-T monitor

On 1 October 2026 the Serbian Ministry of Finance e-invoicing portal (efaktura.gov.rs) announced that update 4.2.0 of the System of Electronic Invoices (SEF) is available on the demo environment, and on the same day published a refreshed “Interno tehničko uputstvo”, the internal technical instruction, dated 1 October 2026. No production date for 4.2.0 has been stated.

This is a technical release within the existing legal framework. It does not change the obligation to issue or receive e-invoices, but SEF versions are binding in practice because every connected ERP and intermediary must work against the version running in production.

Background

SEF is the central system through which all Serbian domestic B2B and B2G invoices are issued, received and reported. The portal publishes numbered versions, first on the demo environment and then in production.

Recent releases were version 4.1.0 (demo 31 July, production 2 August 2026), version 4.1.1 (demo 20 August, production 21 August 2026) and Admin module 2.1.0 (demo 23 September, production 28 September 2026). The amendments to the e-invoicing law in the Official Gazette (No. 80/2026) were announced on 1 September 2026.

The Legislative Change

There is no legislative change. SEF 4.2.0 operates within the existing e-invoicing framework and the Ministry’s technical instruction. It is nonetheless binding in practice: invoices that do not conform to the production system’s behavior are rejected, which is why version releases carry the force of a deadline for integrators even though no penalty is attached.

Scope

According to the document “SEF details of the new version 4.2.0”, published with the announcement, the release contains the following:

• Automatic status update in the Central Invoice Register (CRF). When an invoice is rejected in SEF, the obligation connected to it in the Central Invoice Register automatically moves to the status “Rejected” if it was previously “Active”.

• Exception. The status is not changed where the obligation is already “Started” or “Settled” in the CRF. In that case the invoice becomes “Rejected” in SEF while the CRF status is unchanged.

• Re-acceptance. If an invoice that was rejected is later accepted in SEF, the system automatically notifies the CRF and submits a request to reactivate the corresponding obligation. The request is handled under the CRF’s business rules, whatever the obligation’s current status.

• Performance. The application was optimized to improve overall performance.

The release document does not describe any API changes, validation changes or new fields.

The refreshed Internal Technical Instruction of 1 October 2026 is published as a PDF through the announcement.

The announcement does not say what changed from the previous version, and we have not been able to establish this by comparing the texts. The current instruction covers the EN 16931 Serbian specification identifier, VAT category codes, the electronic address scheme and the application interface methods.

Timeline

• 31 July / 2 August 2026 — version 4.1.0, demo and production.

• 20 / 21 August 2026 — version 4.1.1, demo and production.

• 23 / 28 September 2026 — Admin module 2.1.0, demo and production.

• 1 October 2026 — SEF 4.2.0 on the demo environment; refreshed Internal Technical Instruction published.

• Production date of 4.2.0 — not announced. Earlier releases in this series reached production one to two days after demo, but version 4.0.0 was postponed, so no date should be assumed.

Businesses Affected

Every business and intermediary connected to SEF by API is affected, together with organizations that use the CRF to manage public sector obligations. Businesses that only use the SEF web interface are affected only through changed statuses visible to them.

Required Actions

• Test the rejection and re-acceptance flows against the demo environment if your ERP reads SEF statuses or links invoices to obligations in the CRF.

• Check how your integration treats an invoice that returns from “Rejected” to accepted, since the system will now trigger a reactivation request automatically.

• Download the refreshed Internal Technical Instruction and compare it with the version your integration was built on; the announcement does not list the changes.

• Monitor the SEF portal for the production date and prepare to regression-test on release.

Practical Implications

The status automation reduces manual reconciliation between SEF and the CRF, but it also means that an ERP that previously handled the CRF side manually might now see changes it did not initiate. Where the supplier’s own system pushes status updates to the CRF, there is a risk of duplicate or conflicting updates after production release.

Expected Next Steps

The next step is the production release of 4.2.0, followed by a production notice on the portal. The subordinate acts under the Law on Amendments to the Law on Electronic Invoicing (80/2026) remain to be issued and will be reported separately.

How Can KGT Support You?

KGT delivers SAP-integrated e-invoicing add-ons and SAP Document and Reporting Compliance services, including Serbian SEF connectivity. We regression-test each SEF release against client SAP flows, maintain interface versions as configurable parameters, and monitor the portal so that production cutovers do not disrupt invoicing.

This country update is provided for general information only and does not constitute tax, legal or professional advice.