Serbia: SEF Update 4.2.0 Reaches Production on 2 October 2026 with Automatic SEF–CRF Status Synchronization, and the Ministry Presents the Preliminary VAT Return on 8 October

On 2 October 2026 the Serbian Ministry of Finance e-invoicing portal announced that update 4.2.0 of the System of Electronic Invoices (SEF) is available in the production environment, one day after it appeared on the demo environment on 1 October 2026.

The accompanying details document, dated 2 October 2026, describes two changes to the link between SEF and the Central Invoice Register (CRF) and a performance optimization. Separately, the Ministry is presenting the Preliminary VAT Return within SEF at a workshop on Thursday 8 October 2026, announced on 6 October 2026.

Background

SEF is the central system through which 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.

KGT reported on 2 October 2026 that version 4.2.0 was on demo and that no production date had been announced; that gap is now closed. KGT also reported on 30 September 2026 on the SEF Admin module 2.1.0, which the portal lists as available on demo on 23 September and in production on 28 September 2026, and on 11 August 2026 on the amended e-invoicing rulebook and the Preliminary VAT Return.

The Legislative Change

There is no legislative change. SEF 4.2.0 is a technical release operating within the existing e-invoicing framework and the Ministry’s technical instruction, which the portal re-issued in a version dated 1 October 2026. It is nonetheless binding in practice: invoices that do not conform to the behavior of the production system are rejected, so a version release carries the force of a deadline for integrators even though no penalty attaches to it.

Scope

The details document for 4.2.0 lists three items.

• Automatic status update after rejection. When an invoice is rejected in SEF, the related obligation in the CRF changes to “Rejected” only if it was “Active”. If the CRF obligation is already “Started” or “Settled”, its status stays unchanged, although the SEF invoice still becomes “Rejected”.
• Reactivation after re-acceptance. If a rejected invoice is later accepted in SEF, SEF notifies the CRF and requests reactivation of the related obligation, which the CRF processes under its own business rules regardless of the obligation’s status at that moment.
• Corrections. The application was optimized to improve performance, with no functional details given.

The document does not describe any change to the API, the user interface or validation rules. What changed in the refreshed internal technical instruction of 1 October 2026 relative to its predecessor has not been established.

On the workshop, the portal states that the Preliminary VAT Return will be presented within SEF on Thursday 8 October 2026 from 14:00 to 16:00 at the Ministry of Finance in Belgrade, with a live stream on the portal for those who cannot attend. Registration closed on 7 October 2026 at 12:00 and the question form closed at 16:00 the same day. The content of the presentation has not been published.

Timeline

• 23 September 2026 — SEF Admin module 2.1.0 on demo; 28 September 2026 — in production.
• 1 October 2026 — SEF 4.2.0 on demo; internal technical instruction re-issued.
• 2 October 2026 — SEF 4.2.0 in production; details document dated the same day.
• 6 October 2026 — workshop announced.
• 8 October 2026, 14:00 to 16:00 — workshop on the Preliminary VAT Return within SEF.

Businesses Affected

Every business that issues or receives invoices through SEF, directly or through an ERP or intermediary. The CRF synchronization matters most to businesses that are party to obligations registered in the CRF, because a rejection or re-acceptance of an invoice now changes the linked obligation without any action on their side.

Required Actions

• Regression-test the SEF interface in the demo and production environments against 4.2.0, in particular rejection and re-acceptance flows.
• Review ERP logic that updates CRF obligations itself, because automatic SEF-to-CRF updates may now duplicate or conflict with those updates.
• Compare the 1 October 2026 internal technical instruction with the version in use and document differences.
• Follow the workshop stream and prepare for the Preliminary VAT Return, which links VAT reporting to SEF data.

Practical Implications

The release moves reconciliation work from the business to the system. That reduces manual effort but also removes a control: an obligation can change status because of a rejection that happened elsewhere in the process. For SAP landscapes, accounts payable and receivable teams should know which system is the master for obligation status and should monitor for unexpected status changes after production releases.

Expected Next Steps

The portal is expected to publish further releases, and the subordinate acts under the amended Law on Electronic Invoicing (Official Gazette 80/2026) remain to be issued and will be reported separately. Material from the workshop may clarify the Preliminary VAT Return.

How Can KGT Support You?

KGT is a specialist indirect tax technology firm. We implement and run SAP Document and Reporting Compliance (SAP DRC) and deliver SAP-integrated e-invoicing add-ons where DRC does not yet cover a requirement or where a transformation programme makes a DRC rollout impractical in the available window. Our work is done inside the SAP landscape rather than around it, so VAT determination, document creation, transmission, status handling and reconciliation stay in one place.

For Serbia KGT regression-tests each SEF release against client SAP flows, maintains interface versions as configurable parameters and monitors the portal so that production cutovers do not disrupt invoicing.

This Country Update is provided for general information only and is not tax, legal or professional advice. No reliance should be placed on it without specific advice on the facts of your situation.