Calculating Belgian capital gains tax on crypto: step-up, swaps and the exemption

What exactly you are calculating

Since 1 January 2026, Belgium taxes realised capital gains on financial assets — crypto included — at 10%. The tax falls on the gain, not on the sale proceeds. The calculation takes three steps: fix the right starting value, add up every taxable event, then apply the annual exemption. What the tax covers and why no exchange withholds it for you is set out in the overview article on crypto tax in Belgium in 2026.

Step 1 — the starting value: purchase price or step-up

For crypto bought from 2026 onwards, the starting value is simply your purchase price in euros, fees included.

For crypto bought before 2026, the step-up applies: the taxable gain starts from the value on 31 December 2025, not from your — usually lower — purchase price. Only the gain built up after that date falls under the tax. The mechanism is the same as for shares and ETFs and is explained in the article on the 31 December 2025 step-up value.

One point is harder for crypto than for an ETF: an ETF has a closing price on a regulated exchange, crypto has no single one. Which reference the administration will accept for crypto is not confirmed. So record which source you used for your 31 December 2025 valuation, and keep that record.

Step 2 — adding up every taxable event

Three kinds of transactions count as a realisation:

Transaction	What you need
Sale for euros	sale proceeds minus starting value
Swap from one coin to another	the euro value at the moment of the swap
Paying for something directly in crypto	the euro value at the moment of payment

The second row is the heavy one: according to most sources, a crypto swap is a taxable event, even without ever passing through euros. A portfolio that moves between coins regularly therefore accumulates far more taxable events than it has sales in euros — and each one needs the euro price of that moment.

Step 3 — the annual exemption

From the total gain, the annual exemption is deducted — the same one as for your shares and ETFs. Its amount and how to reclaim it through the tax return are covered in the article on the annual exemption. Note: the exemption is currently a property of the regime. If crypto ends up under a different regime than shares, it is not a given that the exemption reaches crypto — that point is not yet confirmed.

A worked example

You bought a position for €20,000 in 2024. On 31 December 2025 it is worth €45,000. In June 2026 you sell everything for €52,000, with no other realisations that year.

• Starting value: €45,000 (the step-up, not the purchase price).
• Realised gain: €52,000 − €45,000 = €7,000.
• The annual exemption is deducted from that; only the remainder is taxed at 10%.

Measured against the purchase price, the profit was €32,000 — but that figure plays no role in this calculation, provided you can substantiate the step-up value.

Check the numbers

The capital gains tax simulator works through a single sale without uploading anything. For a full year with several transactions, the calculator reads your transaction history directly — how to obtain it from your exchange is covered in the per-exchange export guide.

To be confirmed. Whether crypto falls entirely under the same regime as shares, whether the exemption reaches crypto, which 31 December 2025 reference value will be accepted, and how coin-to-coin swaps are treated in detail: none of this has been confirmed by the FPS Finance at the time of writing. Treat any figure that rests on it as uncertain.

Verify your figures

Belfolio shows this calculation for information only. This is not tax advice. Check your situation with the FPS Finance or your accountant before filing.