Capital gains tax: is it better to opt in or opt out?
March 2026 - Will you have the new capital gains tax on financial assets deducted automatically, or will you arrange everything yourself via your tax return? For many entrepreneurs and private investors, this is not an easy decision.
In 2026, there will be significant changes for those who invest in stocks, funds, or cryptocurrencies. The new capital gains tax means that you will now pay tax on profits realized from the sale of financial assets. However, there is also a choice to be made: will you have that tax deducted automatically, or will you arrange everything yourself via your tax return? For many entrepreneurs and private investors, this is not an obvious decision.
What is capital gains tax?
Capital gains tax is 10% of the profit you make when you sell a financial asset. That profit—the capital gain—is simply the difference between the sale price and the purchase price. If you purchased your investment before January 1, 2026, you can choose to use either the original purchase value or the value on December 31, 2025 as your starting point.
It is important to note that there is an annual exemption of €10,000 per person. In other words, you do not pay tax on the first €10,000 of profit. If you do not use the entire exemption, you can carry over up to €1,000 per year to subsequent years, up to a maximum of €15,000.
If you make a loss on an investment, you can deduct that loss from your capital gains, but only within the same year and within the same category of assets.
Opt-in: automatic deduction
If you opt in, your bank or investment platform will automatically deduct the 10% capital gains tax at the time of sale. This means you will immediately receive the net amount in your account, and the tax authorities will receive the tax directly.
This seems simple, but there is an important nuance: the bank does not automatically apply the €10,000 exemption. This is only settled retrospectively via your personal income tax. This means you may initially pay too much tax, which you will then have to reclaim (in part) later.
The advantage of opting in is that you won't have any surprises when you receive your tax bill. Everything has already been paid, which gives some people peace of mind, especially when large amounts are involved.
Opt-out: arrange it yourself via your tax return
With an opt-out, nothing is automatically withheld. Your bank will report your profits to the tax authorities, but you must declare and pay the tax yourself via your personal income tax return.
The big advantage here is that you can make the most of the exemption and any losses. This is often more interesting for smaller investors in particular, as it prevents you from temporarily paying too much tax.
The disadvantage is that your tax bill for that year may suddenly be a lot higher. You therefore need to be financially prepared for this.
Transition period in 2026
The law requiring banks to automatically withhold tax will not come into full effect until June 1, 2026. This means that any capital gains you realize between January 1 and June 1, 2026 will still be included in your tax return. You can ask your bank to withhold this tax retroactively, but this is not done by default.
From June 2026, opt-in will become the default and you will have to explicitly choose if you prefer to opt out.
So what is the best choice?
There is no universal answer. For those with a limited portfolio who mainly realize small profits from time to time, opting out is usually the most logical choice. You retain control, make optimal use of the exemption, and avoid unnecessary advance payments.
However, if you expect significant added value, for example after selling a substantial position, opting in may be more interesting from both a psychological and practical point of view. The tax is settled immediately and you will not be faced with any unpleasant surprises when you receive your next tax assessment.
In short: those who prefer simplicity and predictability are more likely to opt in. Those who want to optimize their tax situation and keep track of their own files are often better off opting out. For many entrepreneurs, looking ahead to your planned sales can go a long way toward helping you make the right choice.
