Belgium's 2026 capital gains tax: what U.S. citizens need to know

What changed in Belgium

The law of 6 April 2026 introduced a tax on gains from financial assets, effective for gains realised from 1 January 2026, and the tax administration explained it in circular 2026/C/74 of 22 July 2026. It applies under the personal income tax, to gains made outside any professional activity in the normal management of private assets. Gains realised before 2026 stay untaxed, and so does the growth up to 31 December 2025.

There are three regimes, and a sale falls under only the most specific one: an internal gain (shares sold to a company you control, 33%), a substantial holding (you alone held at least 20%, with a €1 million exemption over five years and rates from 1.25% to 10%), and the general regime — 10% — for everything else. Almost every portfolio sale is in the general regime.

Who it reaches

Belgian tax residents. The circular is explicit that the new tax does not apply under the non-resident income tax. An American living in Belgium is therefore taxed by both countries on the same sale: Belgium as the country of residence, the United States as the country of citizenship.

What is covered

Shares, bonds, units of funds, ETFs and ETNs, derivatives and CFDs, life-insurance and capitalisation contracts (branch 21 and branch 23 included), crypto-assets, funds not held on a payment account, and investment gold. Pension savings, group insurance and long-term savings — the second and third pension pillars — are expressly exempt; art, jewellery and wine are outside.

The rate, the exemption and losses

• 10% on the year's net gains under the general regime, without municipal surcharges (ordinary rates apply instead only if lower).
• An annual exemption of €10,000 per person for 2026 income — spouses each have one; for part-year residents it is pro-rated by months.
• Unused exemption can be carried forward, but not before assessment year 2028 (income 2027), at an amount — expected to be €1,000 — still to be fixed by royal decree.
• Losses offset gains only in the same year and the same regime. There is no carry-forward: a loss not used in 2026 is gone.
• No fees or taxes are deducted on either side — not the commission, not the stock-exchange tax.

The 31 December 2025 reference value

For anything bought before 2026, Belgium replaces your purchase price with the asset's value on 31 December 2025: for a listed security, its last 2025 closing price, which your bank's year-end statement shows. A gain is the sale price minus that value — and so is a loss, which means losses that built up before 2026 cannot be deducted.

Until 31 December 2030 you may ask to use your proven historical cost instead, when it is higher. Belgium then uses the AVERAGE cost of that asset held before 2026 (not the cost of the specific lot), and it can bring the gain down to zero but never turn it into a loss. Identical assets bought at different times are matched first-in, first-out, separately for each securities account. If you moved to Belgium in 2026, assets you owned on arrival take their value on your first day of residence instead.

Why your U.S. basis is different

The United States ignores the Belgian reference value: a revaluation by another country is not a sale or exchange, so it changes nothing in your U.S. basis. Your U.S. basis is what you paid, plus the purchase commission, converted into dollars at the exchange rate on the purchase date; the proceeds, less the sale fees, are converted at the rate on the sale date. Converting the euro gain at one rate gives a different — wrong — number, because the dollar moved between the two dates.

The holding period is American too: a gain is long-term only if you held the asset more than one year, counted from the day after you bought it. And the lot sold is the earliest one in the account unless you identified a specific lot to your broker.

The same sale, two gains

In the worked example above, shares bought in 2015 for €20,000, worth €80,000 on 31 December 2025 and sold in 2026 for €100,000 show a Belgian gain of €20,000. After the €10,000 exemption, €10,000 is taxed at 10%: about €1,000. In the United States, the cost is $22,000 (at 1.10 dollars per euro) and the proceeds $116,000 (at 1.16) — a U.S. gain of $94,000. The exchange rates are illustrative; yours are the rates on your own dates.

Can the Belgian tax be credited?

Possibly, and in part — never automatically. Four questions come in order, and each can fail on its own:

1. Which Belgian tax counts. Only tax you legally owed. Belgian banks withhold 10% without applying your €10,000 exemption or your losses; the excess comes back only if you declare the gain on your Belgian return, and a refundable amount is not tax paid for the U.S. credit (Treas. Reg. §1.901-2(e)). The amount withheld is not the amount that qualifies.
2. Where the gain comes from. A U.S. citizen with a tax home abroad has foreign-source gain only if foreign income tax of at least 10% of the gain is actually paid (§865(g)(2)). Below that, the gain is U.S.-source and the Code alone leaves no room in the credit limitation for the Belgian tax.
3. What the treaty adds. Article 22(4) of the 2006 U.S.–Belgium convention lets a U.S. citizen resident in Belgium credit Belgian tax against U.S. tax on income the treaty would leave to Belgium for a non-citizen — share gains, under Article 13(6) — and treats it as Belgian-source to the extent needed. The IRS route is the Publication 514 worksheet attached to Form 1116; no separate category and no Form 8833 for the re-sourcing. Whether Belgium treats a gain on an Irish or Luxembourg fund as U.S. income for this purpose, and how it meets the capital-gain adjustments, are open questions for a professional.
4. What the gain is. If the asset is a non-U.S. fund or ETF, the U.S. gain is a PFIC excess distribution, not a capital gain, and the credit rules for it are narrower still.

Whatever the answer, the credit reduces regular income tax only: it never reduces the 3.8% net investment income tax, which applies once modified AGI passes $200,000 for a single filer. And if Belgium later refunds tax you credited, the U.S. credit must be redetermined on an amended return.

European funds and ETFs: the PFIC question

A UCITS ETF bought on Euronext — usually Irish- or Luxembourg-domiciled — and a Belgian BEVEK/SICAV are funds organised outside the United States, so for a U.S. person they are PFICs whatever they invest in. Selling one is reported on Form 8621; without a QEF or mark-to-market election made in earlier years, the whole U.S. gain is an excess distribution taxed as ordinary income spread over the years you held it, with an interest charge. Belgium meanwhile taxes the same sale at 10% like any other. Directly held shares of operating companies and bonds are not PFICs.

FBAR and Form 8938

A securities account at a Belgian bank or broker — or at a foreign broker such as one based elsewhere in Europe — is a foreign financial account. The FBAR is due once the combined peak of all your non-U.S. accounts passes $10,000 at any moment of the year. Form 8938 applies, for a single filer living abroad, above $200,000 at year-end or $300,000 at any time ($400,000 at year-end for a joint return). Belgium's new tax changes neither test.

Special regimes and exceptions

• A 20% holding held alone, or a sale to a company you or close family control, leaves the 10% regime — a question for a Belgian adviser.
• Very frequent trading, borrowed money or trading bots are the indicators the administration uses to argue speculation, taxed at 33% plus municipal surcharges; the administration has to prove it.
• A life-insurance payout's gain is the payout minus the premiums paid; whether the contract is insurance for U.S. purposes is a separate question a person decides.
• Leaving Belgium is itself taxable as a disposal. Moving within the EU/EEA defers payment automatically; the United States is not on that list, so deferral needs a request and a guarantee. The tax lapses if you do not sell within 24 months. This is not the U.S. expatriation tax (Form 8854), which concerns giving up U.S. citizenship.

Records to keep now

1. Your 31 December 2025 statements for every account — the Belgian reference values, and the evidence if you ever use the historical-cost option.
2. Trade confirmations for every purchase and sale: dates, quantities, prices, fees and the exchange rate applied.
3. The annual Belgian tax slip from each Belgian bank: what was withheld, or the opt-out.
4. For each fund: its ISIN, domicile and any earlier Form 8621 and election.
5. Your Belgian tax assessment once issued — the tax actually owed, which is the figure a U.S. credit can rest on.

Common mistakes

• Using the 31 December 2025 value as the U.S. cost basis — it has no U.S. effect.
• Converting the euro gain at the sale-date rate instead of converting cost and proceeds at their own dates' rates.
• Claiming the amount withheld on Form 1116 instead of the tax actually owed after the exemption.
• Assuming the Belgian tax offsets the 3.8% NIIT — no foreign tax does.
• Reporting a UCITS ETF sale as a capital gain on Schedule D — it is a Form 8621 event.
• Treating every Belgian product as a PFIC, or none: shares and bonds are not; funds and ETFs are; insurance and pension products need a person.

Sources: loi du 6 avril 2026 (Moniteur belge 21 April 2026); circular 2026/C/74 of 22 July 2026; royal decrees of 18 May 2026; SPF Finances; IRC §§865, 901, 904, 1222, 1291, 1411; Treas. Reg. §§1.901-2, 1.988-2, 1.1012-1, 1.1411-1; the 2006 U.S.–Belgium convention and its Technical Explanation; IRS Publication 514. Reviewed against them on 2026-10-17.