Two official Belgian sources were updated after they were first published: the ONSS rate files for the 3rd quarter of 2026, and the FOD Financiën brochure for Belcotax-on-web, income year 2025. If you downloaded either one earlier, replace your copy.
DmfA: rates for the 3rd quarter of 2026
ONSS first published the Q3 2026 rate files on 24/07/2026 as provisional (“sous réserve”). The final version came out on 15/09/2026. Compared with the provisional one:
- Some contribution rates were removed and others added. Employer categories 134 and 350 lose some rates (contribution worker codes 812, 813 and 889). New rates appear mainly for employer category 006, plus categories 417 and 755 to 759.
- Some worker code and employer category combinations changed. New combinations concern categories 006 and 040 (worker codes 016, 017, 675 and 678). Combinations were removed for categories 040, 224, 226, 244, 254 and 497.
- Everything else is unchanged. The reductions and the Decava rates are the same as in the provisional file, and the DmfA file structure has not changed.
What to do: if your Q3 2026 DmfA was prepared with the 24/07/2026 file, check whether any of your employers fall in the categories listed above. If so, check their worker codes and rates against the final file.
Belcotax-on-web: brochure for income year 2025
The brochure now exists in three versions:
- Version 1.0 (05.12.2025): first version.
- Version 2.0 (19.12.2025): fiches 281.63 and 281.87 are removed, and fiches 281.61 and 281.84 are modified, following the law of 18/12/2025 (Belgian Official Gazette of 30/12/2025).
- Version 3.0 (14.01.2026): two corrections to validation rules. In fiche 281.10, the check on the student-job maximum now refers to the right zone (2.227 instead of 2.207). In fiche 281.11, the check on the pension bonus (zone 2.088) is removed.
What to do: work from version 3.0. For standard employee wage certificates (fiche 281.10), only the corrected student-job check affects you.
Looking ahead: FOD Financiën will launch a new Belcotax-on-web from February 2027, for income year 2026. The current application stays in use for income year 2025.
Official sources
These documents are published by ONSS and FOD Financiën. Download them directly from the authorities; they are available in Dutch and French.
- Rate files 2026/3 (final version of 15/09/2026), Excel and XML, in the “Bijdragevoeten / Fichiers des taux” section of the ONSS TechLib page: Dutch · French
- Belcotax-on-web brochure, income year 2025, version 3.0: Dutch (PDF) · French (PDF)
- Belcotax-on-web technical documentation (FOD Financiën): Dutch · French
FiscFort monitors these sources on a fixed schedule and applies changes only after review.
See the platform
Dedicated, EU-hosted infrastructure with an isolated Odoo instance and portal for every client.