Belgium: Details on capital gains tax

Two Royal Decrees provide more detail on the withholding tax, exit tax, and reporting obligation for intermediaries under the newly introduced capital gains tax.

The Royal Decrees become effective on June 1, 2026, but the provisions relating to reporting obligations for intermediaries and certification obligations for the exit tax apply retroactively from April 16, 2026.

Withholding tax credit

Financial institutions established in Belgium are generally required to withhold taxes on realized capital gains when they process qualifying transactions. When applying the withholding tax, they will not take into account the following rules that may reduce the tax base:

• First-tranche annual exemption of €10,000-15,000 (subject to indexation)
• Step-up mechanism for historical gains accrued prior to January 1, 2026
• Offsetting qualifying capital losses

Taxpayers can apply these rules through their personal income tax (PIT) return. In such cases, the taxes withheld will be offset against the final tax liability.

In terms of supporting documentation, the Royal Decree introduces explicit evidence requirements for taxpayers. They must be able to document (upon request of the tax authorities):

• Amount of the realized gains
• Amount of withholding tax effectively withheld
• When relevant, the historic acquisition value or the total amount of insurance premiums paid up to December 31, 2025
• When relevant, the amount of capital losses that have been claimed

Opt-out mechanism

The withholding tax mechanism is optional. Individual taxpayers can choose to opt out of the withholding tax, in which case no tax is withheld and the capital gains are fully settled via the annual individual (personal) income tax (PIT) return. The second Royal Decree specifies the details of this opt-out procedure:

• Form: The choice must be made unambiguously and in writing, which includes technologically governed choice processes
• Deadline: For financial assets, the choice must be made upon opening an account or by the deadline imposed by the broker, which must precede any realizations on the account. For insurance products, the choice is due at the latest upon partial or full liquidation of the product. For realizations between June 1, 2026, and August 31, 2026, the opt-out is due by the deadline imposed by the broker, ultimately by August 31, 2026
• Choices past the deadline: Opt-outs past the deadline will apply beginning the next tax period
• Presumed opt-out for insurance contracts: A presumption of opt-out applies for contracts between June 1, 2026, and August 31, 2026, unless the beneficiary explicitly requests withholding in writing at the latest upon liquidation
• Voluntary payments: For capital gains realized between January 1, 2026, and May 31, 2026, the withholding tax obligation does not apply due to the delayed approval of the legislation. Taxpayers who wish to have voluntary withholding tax applied must request this in writing and unambiguously by the deadline set by the broker and at the latest by August 31, 2026. This request implies that the taxpayer can no longer opt out for the remainder of 2026 for that account or product
• Revoking a previous opt-out: An opt-out that is validly made will apply to all capital gains relating to that account or contract for the relevant tax year. Revoking the opt-out is only possible once per tax year, must be made unambiguously and in writing, and takes effect from the following tax year.

The opt-out is accompanied by reporting obligations for Belgian financial intermediaries (banks, brokers, and insurance companies). When an individual has opted out, the financial institution must file an annual form with the Belgian tax administration by March 1 of the following year. For gains realized prior to June 1, 2026, no reporting is required.

Exit tax: Annual certification requirement for payment deferral

For emigrating taxpayers, an exit tax applies on all latent capital gains on the date of departure. However, the legislation allows for a payment deferral of this exit tax, subject to certain conditions. If no gains are realized within 24 months of departure, the exit tax is definitively canceled.

In case of payment deferral, the tax code imposes an annual certification requirement related to this 24-month monitoring period. Taxpayers who have been granted a deferral must submit the certificate to the Belgian tax administration, either electronically or on paper, no later than the last day of the 14th and 26th month following the month of the date of departure.

The first certificate (due at the end of the 14th month) covers a period of 12 months from the date of emigration. The second covers the period from month 13 to month 24.

Read a May 2026 report prepared by the KPMG member firm in Belgium