Capital Gains Tax 2026 for Cross-Border Workers: Who Taxes You?

Last updated: 2026-05-20

On this page:
1. Your tax residence determines everything: always Belgium
2. What does the double taxation treaty say?
3. My account is with a foreign broker — does that matter?
4. Reference value of 31 December 2025 also applies to cross-border workers
5. NBB CAP: declaring your foreign account
6. Practical checklist

Table of Contents

Introduction

Every day an estimated more than 50,000 Belgian employees commute to Luxembourg (STATEC 2024). Tens of thousands of others cross the border daily into the Netherlands, France, or Germany. You work there, receive your salary there, and pay social contributions there. It is understandable to think: “My investments are related to my work in Luxembourg, aren’t they? Does that country also tax my capital gains?”

That is a reasonable assumption — but an incorrect one. From 1 January 2026, Belgium introduced a new 10% capital gains tax on realised capital gains on financial assets, enacted by the Law of 6 April 2026, Belgian Official Gazette (BS) 21 April 2026 (retrieved 2026-05-20). This law applies to all Belgian tax residents — including those who work full-time across the border. This article explains why, and what you need to do in practice.

1. Your tax residence determines everything: always Belgium

Where are you a tax resident? Not where you work

Belgian personal income tax is based on tax residence, not on where you work. That principle is set out in article 2 §1, 1° of the Income Tax Code 1992 (ITC92) (retrieved 2026-05-20): Belgian residents for tax purposes are natural persons who have their domicile or the seat of their wealth in Belgium. Article 3 ITC92 then provides that these residents are subject to personal income tax.

Domicile in the tax sense is the place where you actually live: your family is there, your home is there, you sleep there. A Belgian who drives to Luxembourg every morning and returns home in the evening to Arlon or Tongeren has his tax residence in Belgium. It does not matter that he earns his entire salary in Luxembourg or that he has a Luxembourg employer.

Seat of wealth is the place from which someone manages their assets. If you manage your investment account from Belgium — even if that account is held at a Luxembourg bank — the management decisions are made in Belgium. This means you also have a Belgian tax residence under this criterion.

Article 5 ITC92: Belgium taxes your worldwide income

Belgian residents for tax purposes are subject, under article 5 ITC92 (retrieved 2026-05-20), to personal income tax on their entire worldwide income — including investment income arising from accounts in Luxembourg, the Netherlands, or elsewhere. Your Luxembourg salary is taxed in Luxembourg (thanks to the double taxation treaty, see § 2), but your capital gains on shares or ETFs are — as a Belgian tax resident — always taxed in Belgium.

Practical takeaway: Do you live in Belgium and work in a neighbouring country? Then you are a Belgian tax resident and fall under the Belgian capital gains tax. Full stop.

2. What does the double taxation treaty say?

The OECD model: the state of residence has the final say on capital gains

Belgium has concluded a Double Taxation Treaty (DTT) with each neighbouring country to prevent income from being taxed twice. For capital gains on movable securities (shares, funds, ETFs), all of these treaties follow the same principle from article 13 of the OECD Model Tax Convention (retrieved 2026-05-20):

Capital gains on movable securities are taxable in the state of residence of the alienator.

In other words: the country where you live (Belgium) has the exclusive right to tax your investment gains. The country where you work has no taxing rights over those gains.

Your neighbouring country per situation

Country of employment	Treaty with Belgium	Capital gains on shares/ETFs: who taxes?
Luxembourg	Belgian-Luxembourg Treaty of 17 September 1970, amended by Protocol of 5 December 2017 + Amending Protocol of 31 August 2021	Belgium (state of residence)
Netherlands	Belgian-Dutch Treaty of 2001	Belgium (state of residence)
France	Belgian-French Treaty of 1964, as amended	Belgium (state of residence)
Germany	Belgian-German Treaty of 11 April 1967, amended by Additional Protocol of 5 November 2002	Belgium (state of residence)

In each of these treaties the rule is the same: capital gains on ordinary shares, ETFs, and investment funds are taxed exclusively in the state of residence — in your case Belgium. Luxembourg, the Netherlands, France, and Germany do not levy capital gains tax on your investment portfolio, as long as you are resident in Belgium.

Exception 1: capital gains on shares in real-estate companies and on real property itself can (in part) be taxed by the source country, but that falls outside the scope of this article.

Exception 2 (specific to BE-NL): art. 13 §5 of the BE-NL Treaty of 2001 also allows the Netherlands to levy tax when a Belgian resident directly or indirectly holds ≥5% of the capital of a Dutch company (a lower threshold than the Belgian domestic substantial-participation rule). Do you hold such a stake? Consult a tax specialist about the specific treaty allocation.

Your Luxembourg salary: a separate question

Your salary earned in Luxembourg is a different matter: that salary is generally taxed in Luxembourg (source state), and Belgium grants an exemption with a progression clause (or a tax credit, depending on the exact type of income). But that allocation of employment income does not affect your investment capital gains. The two streams — employment income and investment income — each fall under their own treaty article. Your capital gains on shares and ETFs: always Belgium.

3. My account is with a foreign broker — does that matter?

Account location ≠ tax location

Many cross-border workers to Luxembourg keep their investment account with a Luxembourg bank or broker (Saxo Bank Luxembourg, BGL BNP Paribas, ING Luxembourg, Swissquote). Cross-border workers to the Netherlands sometimes work with an account at a Dutch institution (Degiro, Flatex, ABN Amro). The reasoning is understandable: “I earn in Luxembourg, I keep my account there, so they handle it themselves.”

That reasoning is not fiscally correct. The residence of the investor determines the tax liability, not the location of the account. You are a Belgian tax resident → you pay Belgian capital gains tax → even if your investment portfolio is held at a Luxembourg bank.

No automatic Belgian withholding with a foreign broker

A Belgian broker (Bolero, Keytrade, MeDirect, Saxo Bank Belgium) withholds the 10% capital gains tax automatically at source from 1 June 2026. This is the so-called “broker withholding obligation” under the Law of 6 April 2026 (retrieved 2026-05-20).

A foreign broker (Luxembourg bank, DEGIRO NL, Interactive Brokers Ireland, Trade Republic Germany) has no Belgian withholding obligation. It withholds nothing. This means that as a cross-border worker with a foreign account you must declare your capital gains yourself on Tax-on-Web in your personal income tax return for tax year 2027 (covering income year 2026). This is the “self-declaration path” — also referred to as Path 2 in the capital-gains-tax declaration guide. See also Capital Gains Tax 2026: declaration and Tax-on-Web for the step-by-step procedure.

Practical takeaway: Do you have an account with a foreign broker? Set a reminder for spring 2027 to declare your capital gains. There is no automatic withholding that covers you.

4. Reference value of 31 December 2025 also applies to cross-border workers

The step-up cost basis applies to everyone

The 10% capital gains tax is calculated on the net capital gain: sale price minus acquisition price. For assets purchased before 1 January 2026, the law provides that the market value on 31 December 2025 serves as the fiscal acquisition price — the so-called reference value (foto-waarde). You are therefore taxed as if you had repurchased everything on 31 December 2025. This is set out in the Law of 6 April 2026 (retrieved 2026-05-20). This rule applies to all Belgian tax residents, including cross-border workers.

Foreign brokers do not produce a Belgian overview

Belgian brokers (Bolero, Keytrade, MeDirect) track the reference value internally for their withholding obligation. Foreign brokers in principle do not — they are not subject to Belgian rules. This means you must yourself:

Download or request a portfolio overview as of 31 December 2025 from your foreign broker.
Retain that overview as a tax record (digital or printed, dated in your name).
If your broker cannot provide a historical overview: closing prices on 31/12/2025 can be reconstructed from market data (see the detailed guide Reference Value 31 December 2025 for ETFs and crypto: how to prove it).

You may also use your actual historical purchase price if it is higher than the reference value — this is permitted until 31 December 2030 (after which only the reference value applies).

Practical takeaway: Do you have an account with a foreign broker? Request a historical account statement for 31 December 2025 from your broker today, or take a screenshot of your portfolio position on that date.

5. NBB CAP: declaring your foreign account

Declaring foreign accounts via Tax-on-Web

Belgian tax residents are legally required to declare foreign bank and investment accounts in their annual tax return via Tax-on-Web (section “foreign accounts”). This declaration is forwarded to the Central Contact Point (CAP) of the National Bank of Belgium (NBB) (retrieved 2026-05-21). This also applies to your Luxembourg salary account or investment account — even if you have never thought about it.

What changes as of 1 December 2026?

From 1 December 2026 the NBB CAP will be expanded: banks and brokers must not only report the existence of securities accounts, but also the individual content per account (which securities, how many units, what value). FPS Finance will be able to consult that data for tax audits. This applies to Belgian institutions — but the declaration by the taxpayer themselves (for foreign accounts) remains required unchanged. See also NBB CAP expansion 1 December 2026: tax authority gets securities data.

Practical takeaway: Do you have a Luxembourg, Dutch, or other foreign investment account? Tick the “foreign accounts” section in your Tax-on-Web return and provide the account holder, institution, and country.

Visual overview: who taxes your capital gains as a cross-border worker?

Decision tree: if you live in Belgium, you pay Belgian capital gains tax — regardless of where you work or where your account is held. Source: art. 2 §1, 1° + art. 3 ITC92 + Law of 6 April 2026 + double taxation treaties. (retrieved 2026-05-21)

Practical checklist for cross-border workers

Concrete steps you can take today:

Determine your tax residence. Do you live, eat, and sleep in Belgium? Then you are a Belgian tax resident and fall under the Belgian capital gains tax — regardless of your country of employment.
Check the type of your broker. Is your investment account with a Belgian broker (Bolero, Keytrade, MeDirect, Saxo Bank Belgium)? Then that broker automatically withholds 10% from 1 June 2026. Foreign broker? Then you file the declaration yourself on Tax-on-Web in spring 2027.
Request your reference value from your foreign broker. Download or request a historical portfolio overview with the position as of 31 December 2025 (closing prices in your name). Keep this document. Have you not kept anything? Consult Reference Value 31 December 2025: how to prove it.
Declare your foreign account(s) in your Tax-on-Web return. All foreign bank and investment accounts must be listed in the “foreign accounts” section. This also applies to your Luxembourg salary account or your Dutch investment account.
Follow the declaration procedure for tax year 2027. In spring 2027 you declare your capital gains in your return. See the step-by-step guide Capital Gains Tax 2026: declaration and Tax-on-Web.
Consult a tax specialist in complex situations. Do you have multiple nationalities, live partly in two countries, or hold a substantial participation in a company? Then personalised advice from a tax adviser is recommended.

Sources & further reading

Primary sources

Law of 6 April 2026 introducing a tax on capital gains on financial assets — full text (ejustice Justel, NUMAC 2026002780) (retrieved 2026-05-20)

ITC92 consolidated text — art. 2 §1, 1° (definition resident / tax domicile), art. 3 (subjection to personal income tax) and art. 5 (taxability of worldwide income) (retrieved 2026-05-21)

OECD Model Tax Convention on Income and Capital — art. 13 capital gains (retrieved 2026-05-20)

FPS Finance — Capital Gains Tax (official information page) (source in Dutch — no English version available; retrieved 2026-05-21)

NBB Central Contact Point (CAP) — official NBB page (retrieved 2026-05-21)

Wikifin — Tax, work and income (FSMA education portal) (retrieved 2026-05-20)

Secondary sources and further analysis

Moore Law — New capital gains tax: what do we already know? (confirmation Belgian Official Gazette 21 April 2026) (retrieved 2026-05-20)

EY Belgium — The new Belgian Capital Gains Tax: what changes in 2026 (retrieved 2026-05-21)

Related articles on investnow.be

Capital Gains Tax 2026: declaration and Tax-on-Web — Step-by-step declaration guide
Reference Value 31 December 2025 for ETFs and crypto: how to prove it — Proof for your fiscal acquisition price
NBB CAP expansion 1 December 2026: tax authority gets securities data — What the CAP expansion means for your foreign account
Reynders tax vs capital gains tax: are you taxed twice? — For holders of bond ETFs