Belgium Tax Filing Procedures Guide

Online Portals

• MyMinfin / Tax-on-Web (individuals): The online platform for personal income tax (personenbelasting / IPP). Available at MyMinfin.be or via the Tax-on-Web application. Features: (a) pre-filled return (vooringevulde aangifte / déclaration préremplie) from early May, (b) online filing by 15 July (15 October for tax intermediaries), (c) view assessment notices (aanslagbiljet), (d) make payments or request instalments, (e) update personal details (address, bank account). The system is accessible via eID (electronic ID card), itsme app, or a token.
• BizTax / Belcotax (companies): The corporate tax filing portal. BizTax is used for: (a) filing the corporate tax return (Vennootschapsbelasting — ISOC), (b) filing the annual accounts (in integrated format), (c) making payments and viewing assessments. The portal supports the "Vennootschapsbelasting 2" form. Filing is mandatory electronic for all companies.
• Intervat (VAT): The VAT return portal. Used for: (a) filing periodic VAT returns (monthly or quarterly), (b) filing the annual BTW-listing, (c) filing the ICAR (Intracommunautaire Aangifte). Intervat is accessible via eID or itsme. The system is integrated with accounting software through the "Intervat Connect" API.
• DMFA (payroll — RSZ/ONSS): The social security declaration portal. Employers file the multifunctional declaration (DMFA/DmfA) monthly — reporting all employees' wages, social contributions, and withholding tax. The portal is accessible via the social secretariat (social secretariaat / secrétariat social) or directly.

Key Deadlines

• Personal income tax: Tax year = current year (e.g., income year 2025 → tax year 2026). Paper return: 30 June. Online return (Tax-on-Web): 15 July. Via accredited intermediary: 15 October. The assessment notice is issued between June and October of the following year. Payment is due within 2 months of the assessment date.
• Corporate tax: The return is due within 6 months of the balance sheet date (7 months for electronic filing). Prepayments (voorafbetalingen): 10 April, 10 July, 10 October, 20 December. Underpayment penalty: 6.75% (increasing to 9% from 2027).
• VAT: Monthly or quarterly return due by the 20th of the following month. Payment due by the same date. BTW-listing: 31 May annually. ICAR: 20th of the following month (monthly if supplies exceed €100K/year, quarterly if below).
• Payroll (DMFA): Monthly, due by the 15th of the following month. Bedrijfsvoorheffing (withholding tax) payment due by the 15th.

Prepayment System (Voorafbetalingen / Versements Anticipatifs)

• Personal income tax: Individuals with significant non-withheld income (freelance, rental, foreign income, capital gains) should make quarterly prepayments to avoid a 2.25% penalty on the tax due (the "verhoging van de belasting" / "majoration de l'impôt"). The prepayment is calculated as a percentage of the estimated tax due. Four instalments: 10 April, 10 July, 10 October, 20 December. The penalty is avoided if prepayments equal at least 105% of the final tax (for personal income).
• Corporate tax: Companies must make quarterly prepayments. The penalty for insufficient prepayments is 6.75% (increasing to 9% from 2027 on the shortfall). The prepayment is calculated as: estimated tax liability × mandatory percentage. The penalty is fixed — it cannot be waived for cash flow reasons.

Assessment Notice and Objections

• Assessment notice (Aanslagbiljet / Avis d'imposition): After filing the return, the tax authorities issue an assessment notice. The notice shows: taxable income, tax calculated, prepayments made, tax credits claimed, and the amount due or refund due. The assessment must be checked carefully for errors (especially the pre-filled data — banks, employers, insurers).
• Objection (Bezwaar / Réclamation): If the assessment is incorrect, the taxpayer can file an objection within 6 months of the assessment date (the date on the aanslagbiljet). The objection must be in writing (via MyMinfin or by registered letter) and must state the grounds for the objection. The tax authorities have 6 months to respond. If they reject the objection, the taxpayer can appeal to the Rechtbank van eerste aanleg / Tribunal de première instance (court of first instance).
• Tax ruling (SDA / DVB — Dienst Voorafgaande Beslissingen / Service des Décisions Anticipées): Belgium's advance tax ruling system allows taxpayers to obtain binding confirmation from the tax authorities on the tax treatment of a specific transaction or structure. The ruling is valid for 5 years (certain cases: renewable). The ruling can cover: transfer pricing methodology, VVPR-bis application, expat regime eligibility, NID calculation, and restructuring. The ruling request must be submitted before the transaction takes place and must include a full description of the facts and legal analysis. The SDA/DVB typically responds within 3–4 months.

For related reading, see our Personal Tax Guide →, Corporate Tax Guide →, and VAT/BTW Guide →.