How MeerwaardeTool computes your capital gains tax

Realised capital gains on financial assets are taxed at a flat 10%, unless adding them to your other income (globalisation) is more favourable.

No municipal surcharge is added to this tax. The 10% really is 10%.

The first € 10,000 of gains each year is exempt. That amount applies to income year 2026; it is indexed every year, and the amounts for 2027 onwards are not fixed yet.

The exemption is per person. On a joint return each partner has their own exemption, for the gains he or she has to declare.

In MeerwaardeTool: A couple with common property sets the household status in MeerwaardeTool; your exemption is then doubled to € 20,000.

The first € 1,000 slice of your base exemption can be carried forward: whatever you do not use of it in a year, you may add on top of your exemption the following year. If you use € 200 of exemption in 2026, for example, you carry € 800 into 2027 (€ 1,000 minus € 200). If you use € 1,000 or more, you carry nothing.

The supplementary exemption you build up never expires. You can use at most € 5,000 of it per year, oldest build-up first, and it is used before your base exemption.

The often-quoted "maximum € 15,000 after five years" is the ceiling on what you can exempt in a single year (€ 10,000 base plus € 5,000 supplementary), not an expiry date.

Losses reduce your gains, but only within the same year, for the same taxpayer and within the same category. A loss you cannot offset this year is lost: carrying it forward to a later year is not possible.

For a security you already held before 2026, the loss is measured from its value on 31 December 2025. Such a loss is deductible even if you made a profit over the whole holding period (see the historical purchase price below).

If you bought the same security in several purchases, a sale is deemed to take the oldest purchase first. Units you already held before 2026 go first, at their value on 31 December 2025; later purchases follow at their actual purchase price.

A sale that draws on several purchases stays one transaction with one result: gains and losses on the different units are netted within that sale.

If you hold the same security on more than one securities account, FIFO runs separately on each account. Accounts are never added together, not even at the same broker: two accounts at one broker are two separate queues.

So it matters which account you sell from.

For securities you already held before 1 January 2026, the value on 31 December 2025 counts as the purchase value. For a listed security that is the last closing price of 2025. Only the gain after that date is taxable.

You only have to show that you held the security before 2026; any means of proof will do except an oath.

If you bought a security before 2026 for more than its value on 31 December 2025, you may use your actual purchase price instead of the snapshot value for a sale up to and including 31 December 2030. You must be able to prove that price yourself. It is the average purchase price of the units you still held on 31 December 2025.

That choice can only reduce your gain to zero, never turn it into a deductible loss. A loss against the snapshot value itself does remain deductible, even if you made a profit over the whole holding period. From 2031 the snapshot value always applies.

In MeerwaardeTool: If you already sold part of the position before 2026, MeerwaardeTool uses a running weighted average. The circular gives no example of that case.

Brokerage fees, transaction costs and the stock-exchange tax (TOB) may not be deducted from your gain or added to your purchase price. The gain is computed on the gross purchase and sale price.

If you buy or sell in a foreign currency, both the purchase and the sale are converted to euro at the exchange rate of the day of that transaction. Only the gain in euro counts.

An exchange-rate movement alone can therefore create a taxable gain, even if the dollar price stayed the same. MeerwaardeTool uses the European Central Bank reference rate.

Since 1 June 2026 Belgian banks and brokers withhold 10% withholding tax on your gains on securities (opt-in). They must ignore your exemption, your losses and a higher historical purchase price when doing so. Too much is therefore often withheld.

What was withheld in excess you reclaim through your tax return for the year of the sale, with supporting documents. No return, no refund.

With opt-out nothing is withheld and you declare yourself. You make that choice per account, together with all holders; a later choice or a revocation only takes effect from the following year. With a foreign broker such as DEGIRO or MEXEM nothing is withheld and you always declare yourself.

In MeerwaardeTool: MeerwaardeTool shows your tax under both filing modes: through the broker (opt-in, everything at the reference price of 31/12/2025) and declaring yourself (opt-out, the most favourable tax basis per position), with your exemption and your losses. That way you see which choice costs you the least. What your bank actually withheld is not read from your import: you find that amount on your bank’s tax certificate.

An action by the company itself is only a sale when something leaves your assets in exchange for a counter-value. This is how the common cases are handled:

• AppliedSplit and reverse split: not a sale. Purchase value and snapshot value are spread over the new number of shares; the total stays the same.
• AppliedCash for a fraction of a share: a sale of that fraction on the day of the action.
• AppliedStock dividend or optional dividend taken in shares: a purchase at the value of the shares on the day you receive them, never at zero.
• PartialShare-for-share exchange (merger, exchange offer): tax-neutral. The purchase value carries over to the new shares, with the value of the original shares on 31 December 2025 as a floor. An exchange offer paid entirely in cash is a sale. An offer in cash and shares together has to be entered manually.
• Not yetSpin-off: MeerwaardeTool still gives the new shares a purchase value of zero, while the law prescribes a split of the purchase value or the taxed dividend value.
• PartialReturn of capital: recorded, without lowering the purchase value of your shares. The circular says nothing about it; MeerwaardeTool follows the literal text of the law.

An option is a financial instrument; what is taxable is what gets transferred at settlement. MeerwaardeTool follows the practice of the Belgian brokers that withhold: every option leg is settled on its own.

A bought option that you sell gives a gain or a deductible loss. So does a written option that you buy back. An option that expires worthless gives nothing: a premium paid is then not a deductible loss, a premium received is not a gain. On exercise or assignment there is no result on the option itself; the strike price becomes the purchase or sale price of the shares.

In MeerwaardeTool: Options are read from MEXEM statements or entered manually.

No article of law or circular explicitly covers a private investor’s short sale. MeerwaardeTool treats it as an ordinary 10% gain, realised on the day you buy the position back: the result is what you received on the sale minus what you paid on the buy-back.

The tax authorities can tax a gain as speculation at 33%, but they have to prove it themselves, on a combination of factors. Frequent, leveraged shorting is one such factor.

In MeerwaardeTool: Short sales are recognised in MEXEM statements. DEGIRO and Saxo statements do not say whether a transaction opens or closes a position.

Bonds fall under the capital gains tax. When the issuer repays a bond, however, whatever is paid above the issue price is interest, not a gain; you pay withholding tax on that part.

MeerwaardeTool records bonds from your import, but counts the full price difference as a gain: the interest part above the issue price is not split off yet.

Investment gold falls under the capital gains tax: bars of at least 995/1000 and coins of at least 900/1000 minted after 1800. A Belgian bank withholds nothing on it, so you always declare it yourself.

Physical gold cannot be recorded as a security in MeerwaardeTool yet. A listed gold ETC is processed, as an ETF.

Foreign-currency cash on your investment account is itself a financial asset, because such an account is not a payment account. Every time you use that currency (exchange it back to euro, into another currency, or buy a security with it) you realise a gain or a loss. Only a bank’s foreign-currency current or savings account is excluded.

MeerwaardeTool does not process currency conversions on import yet, so these gains are not computed yet.

For funds that invest more than 10% in debt, the Reynders tax still exists. Where it applies, the Reynders income (30%) is computed first and deducted from the gain; only the rest falls under the capital gains tax, after the exemption. That way the same amount is not taxed twice.

MeerwaardeTool does not apply that deduction yet: the full gain on such a fund goes into the 10% calculation.

The law has three categories. MeerwaardeTool only computes the ordinary investor category: the 10% on other financial assets.

Not covered are internal gains (you sell shares to a company that you control, alone or with family: 33%, no exemption) and a substantial shareholding (at least 20% of one company: its own progressive rate up to 10%, with an exempt first bracket of € 1 million). Losses do not cross categories.