Belgium Employee Payroll — Bedrijfsvoorheffing, ONSS & Fiches 281.10

Collect all master data needed before any payroll computation can begin: employment contract type, joint committee (paritair comité / commission paritaire), gross agreed salary, family situation for withholding, and any sector-specific benefits. The applicable PC/CP determines minimum wage scales, 13th-month obligations, meal-voucher rules, and overtime premiums that override the national defaults.

Calculate both the employee personal ONSS deduction (13.07% of gross, no cap) and the employer ONSS contribution (~27–28% depending on sector), applying the structural reduction formula and any applicable target-group reductions (first-hire exemption, under-26, 55+, long-term unemployed). From 1 July 2025 the basic employer contribution is capped at EUR 85,000 gross per quarter per employee. Also apply the werkbonus / bonus à l'emploi for employees earning below approximately EUR 2,900/month.

Apply Annex III of AR/CIR 92 to the post-ONSS taxable base to determine the monthly withholding tax. The computation uses the employee's family situation code and dependent-child reductions (EUR 48/month for the 1st child, EUR 133 for the 2nd, EUR 299 for each additional). Special rates apply to holiday pay (vakantiegeld/pécule de vacances), the 13th month, and double holiday pay (dubbel vakantiegeld — upper portion withheld at 85%). The fiscal work bonus reduces the withholding proportionally to the social work bonus granted in phase 2.

Compute the final net salary by subtracting employee ONSS (net of werkbonus) and bedrijfsvoorheffing from gross, then add any non-taxable reimbursements: commuting allowance (fietsvergoeding or public transport), meal vouchers (max EUR 6.91 employer share / EUR 8 total), eco-cheques (max EUR 250/year), and the employer contribution to group insurance (groepsverzekering). Verify the net is at or above the applicable minimum wage net equivalent. Produce the legally required payslip.

File the quarterly DmfA (Déclaration multifonctionnelle / Multifunctionele Aangifte) with ONSS/RSZ within the legal deadline (end of the month following the quarter: 30 April, 31 July, 31 October, 31 January). Remit the bedrijfsvoorheffing to SPF Finances / FOD Financiën by the 15th of the month following payment (or the next working day). Small employers qualifying as kleine onderneming may file BV quarterly. Confirm IBAN and payment reference (structured communication using employer ONSS number).

At year-end, compile the annual fiche 281.10 (salary fiche for employees) summarising total gross remuneration, total bedrijfsvoorheffing withheld, ONSS paid, benefits in kind, and other codes required by SPF Finances. Submit all fiches 281.10 electronically via Belcotax-on-Web (BOW) by 28 February of the following year. Also prepare the récapitulatif / samenvattende opgave (form 325.10) that accompanies the fiches. Employee copies must be provided so they can verify pre-populated elements of their personal Tax-on-Web declaration.