Effective 1 June 2026, the Royal Decree of 18 May 2026 introduces an opt-out mechanism for capital gains on financial instruments and certain life insurance contracts.
Belgium’s Ministry of Finance has published a Royal Decree implementing the Capital Gains Tax on shares and crypto assets from 2026. The decree of 18 May 2026 was officially published in Official Gazette No. 2026003829 on 27 May 2026.
A central feature of this legislation is an “opt-out” mechanism, allowing taxpayers to choose whether they want their financial intermediaries to withhold taxes automatically or if they prefer to handle the reporting themselves. These regulations establish strict administrative requirements, including the mandate that any choice to bypass withholding must be made in writing and unequivocally within specific timeframes.
Furthermore, transitional measures are outlined to facilitate the shift to this new tax regime between June and August 2026. Ultimately, the decree seeks to standardise how financial institutions report realised gains and identify account holders to the federal government.
Below are the additional details for each section regarding the Royal Decree of 18 May 2026, and its implementation of the optional withholding tax:
The “opt-out” mechanism
The primary goal of this mechanism is to allow taxpayers to avoid the “pre-financing” of taxes by choosing to settle their tax liability through their annual tax return rather than through immediate withholding at the source.
The decree defines “written” broadly as any form of durable registration that allows for the unambiguous verification of the taxpayer’s intent. The expression of this choice is considered neutral under Article 5.30 of the Civil Code. This includes checking a box in a digital application or submitting a form, whether physical or electronic.
Scope of assets
While the broader capital gains tax introduced by the Law of 6 April 2026 covers four categories—financial instruments, insurance contracts, crypto-assets, and gold/currency—the optional withholding tax system is narrower.
- Included assets: It only applies to financial instruments (Art. 92, § 1, a) WIB 92) and specific life insurance contracts (Art. 92, § 1, b) WIB 92).
- Excluded assets: Consequently, capital gains on crypto-assets and investment gold or currency are not eligible for this optional withholding system.
Timing for the exercise of choice
The timing for making this choice is strictly regulated to ensure administrative clarity:
- Financial instrument accounts: The choice must be made when the account is opened or, at the discretion of the debtor (e.g., the bank), on a specific date determined by them, provided it is before the first taxable capital gain transaction is executed on that account.
- Insurance contracts: The choice must be expressed at the latest when the contract is liquidated.
- Legal entities: For legal entities subject to the tax on legal entities (rechtspersonenbelasting), the same opt-out choice is available and must be managed via their specific account/contract arrangements.
Transitional measures for 2026
These measures were established to allow financial intermediaries (banks and insurers) sufficient time to prepare operationally for the new system.
For accounts where a gain is realised before 1 September 2026, the choice to opt out must be made by 31 August 2026. This choice then retroactively applies to the entire 2026 income year.
For insurance gains paid between 1 June and 31 August 2026, an automatic opt-out is presumed to protect taxpayers while systems are being updated.
If no taxable transaction occurs during this transition period (June-August 2026), the standard rules for opening new accounts apply.
Revocation of choice
Taxpayers are not permanently bound by their initial choice, but changes are restricted to ensure administrative stability. Any revocation can only be made once per calendar year and must be submitted in writing. Moreover, any change does not take immediate effect and will only apply from the following taxable period.
Administrative reporting (The annual sheet)
When the opt-out is exercised, the debtor (the financial intermediary) must ensure the tax administration receives the necessary data via an annual information sheet.
The sheet must be sent electronically in a format determined by the Minister of Finance or their delegate. The report must include the total amount of capital gains realised, the identification data of the account holder/beneficiary, and the specific account or contract number.
This must be submitted by March 1st of the year following the realisation of the gains.
Data protection and privacy
The decree was reviewed by the Data Protection Authority (GBA) to ensure compliance with constitutional requirements on the essential elements of data processing. Following advice from the Council of State, the requirement to report taxpayers’ date of birth was removed due to the absence of a clear legal basis under WIB 92.
Debtors must retain records of taxpayers’ choices and related gains for the standard statutory retention periods under Articles 315 and 315bis of WIB 92. Required identification data is limited to name, address, and national register or company (KBO/CBE) numbers.
The decree was signed by the King on 18 May 2026, and officially entered into force on 1 June 2026. This date was chosen to align with the implementation timeline set by the Law of 6 April 2026.
