Belgium–US taxation: which country taxes what?

Who taxes what?

US pensions: 401(k), IRA and Roth IRA

The treaty taxes private pensions only in the country of residence (Article 17). For a Belgian resident, a 401(k) or traditional IRA payout is therefore taxable in Belgium. The rate is the difficult part: Belgium’s 10% or 16.5% rates for supplementary pensions are not automatic for a US plan, and a lump sum that does not qualify can be taxed at progressive rates up to 50%, plus the communal surcharge. A qualified Roth IRA distribution is exempt in the US, and the treaty requires Belgium to exempt it too. For a large balance, ask for an advance ruling before withdrawing.

US withholding on retirement payouts

US plans generally withhold 30% on payments to foreign recipients unless a valid W-8BEN supports the treaty rate. Withholding is not always the final tax: an overwithheld amount may require a US return to recover. Before age 59½, the US also applies a 10% early-distribution penalty on traditional IRA withdrawals, which the treaty does not remove.

US citizens and green card holders in Belgium

The US taxes its citizens on worldwide income wherever they live, and the treaty preserves that right (the “saving clause” in Article 1). A US citizen living in Belgium therefore files in both countries: Belgium as country of residence, the US with credits for Belgian tax. Former citizens and long-term green card holders can remain taxable in the US for ten years after leaving.

US LLCs owned from Belgium

A single-member LLC that the US ignores for tax purposes can be treated by Belgium as a separate company. If it is managed from Belgium, it can become a Belgian company taxed at 25% (20% on a first tranche for small companies), and its profits can be taxed again as dividends at 30%. Some LLCs also fall under the Belgian Cayman tax, with a reporting obligation in the Belgian return.

US bank and brokerage accounts

Accounts held in the US must be reported in the Belgian return (code 1075) and to the Central Point of Contact of the National Bank of Belgium. US brokers do not withhold Belgian taxes: dividends, interest and, from 2026, capital gains must be declared by the investor. Gains accrued up to 31 December 2025 are exempt.

Social security

The Belgium–US social security agreement prevents double contributions. An employee sent temporarily from one country to the other stays covered at home with a certificate of coverage. Self-employed people are covered where they live.

Frequently asked questions

Is my 401(k) taxed in Belgium or in the US?

In Belgium, if you are a Belgian tax resident, under Article 17 of the treaty. The US may still withhold at payout, and US citizens remain taxable in the US.

Is a Roth IRA tax-free in Belgium?

A qualified Roth distribution is exempt in the US, and the treaty requires Belgium to exempt it as well. Check that the distribution is qualified before relying on it.

Do I pay the 10% early withdrawal penalty if I live in Belgium?

Yes, the US 10% additional tax on traditional IRA withdrawals before 59½ generally still applies, and Belgian tax does not offset it.

I am a US citizen living in Belgium: do I file in both countries?

Yes. Belgium taxes you as a resident, and the US taxes citizens on worldwide income; the treaty avoids double tax through credits.

Is my US Social Security pension taxed in Belgium?

No. Under the treaty, US Social Security benefits are taxable only in the US.

Do I need to declare my US brokerage account in Belgium?

Yes: in the annual return (code 1075) and to the Central Point of Contact. Dividends, interest and capital gains on that account must be declared yourself.