US Expat Taxes in Belgium: How to File and Avoid Double Tax

Belgium taxes its residents more heavily than almost anywhere else in the world, layering a municipal surcharge, the communal tax, on top of an already steep progressive national rate, and Americans who land in Brussels or Antwerp for an EU institution posting, a NATO assignment, or a corporate transfer discover fast that this high local tax bill does not replace their US return, it sits alongside it. FPS Finance wants a Belgian filing every year and the IRS wants a Form 1040 for the same year, and because Belgian tax is so often higher than the equivalent US tax, most of the actual planning here is about making sure that high Belgian bill is put to work as a credit rather than becoming a bill you pay twice.

Do US Citizens Living in Belgium Have to File Both Belgian and US Tax Returns?

Yes, in almost every case. Belgium taxes individuals who are resident there on their worldwide income through FPS Finance, known locally as SPF Finances in French and FOD Financien in Dutch. The United States separately taxes its citizens and green card holders on worldwide income no matter where they live, a rule that has nothing to do with Belgian residency and everything to do with US citizenship or immigration status.

That means the two filing obligations run independently of each other. Filing and paying tax in Belgium does not excuse you from filing a US Form 1040, and filing a US return does not excuse you from your Belgian obligations. The mechanisms that keep the same dollar of income from being taxed twice, the Foreign Earned Income Exclusion, the Foreign Tax Credit, and the US-Belgium tax treaty, operate on the US side of that equation, not as a substitute for either filing.

How Does Belgium Tax Residents on Worldwide Income?

Belgium applies progressive national income tax rates to worldwide income for anyone who qualifies as a tax resident, and on top of the national tax, municipalities add their own communal surcharge calculated as a percentage of the federal tax bill. That combination generally makes Belgium a high-tax jurisdiction, and confirming current-year rates and surcharge percentages before you plan around them is essential since both change from year to year and from municipality to municipality.

Belgium also runs the special tax regime for inbound taxpayers and inbound researchers, introduced in 2022, which can meaningfully change how a newly arrived American's compensation is taxed at the Belgian level. In broad terms, it lets an employer treat certain assignment-related costs, the kind of expenses tied to relocating for and carrying out the Belgian assignment, as a reimbursement excluded from the employee's Belgian taxable pay rather than as additional salary, for employees and researchers who meet its qualifying conditions. The regime's eligibility rules and current terms are specific and can shift, so confirm with a Belgian tax advisor whether your assignment qualifies before assuming it applies.

Should You Claim the FEIE or the Foreign Tax Credit on Belgian Income?

For most Americans earning wages in Belgium, the Foreign Tax Credit on Form 1116 is the stronger tool, because Belgian tax generally runs higher than the comparable US federal rate on the same income. When that is true, the credit can eliminate US tax on your Belgian-source income entirely and still leave unused credit on the table, which is why higher earners in Belgium typically favor the Foreign Tax Credit over the exclusion.

The Foreign Earned Income Exclusion on Form 2555 works differently: it excludes foreign earned income up to an annually indexed maximum, for example $130,000 for 2025, from US taxable income in the first place under IRC §911. That can be simpler for income under the cap, but it comes with real costs. The FEIE does nothing for self-employment tax, claiming it can disqualify the refundable Additional Child Tax Credit for a family with kids, and once you revoke the election you generally cannot re-elect it for five years without IRS consent. The Foreign Tax Credit, by contrast, is computed by category under IRC §§901 and 904, and any credit you cannot use in the current year carries back one year and forward ten years on Schedule B of Form 1116, which you can use in a future year when your foreign taxes fall below the Form 1116 limit. Our FEIE versus Foreign Tax Credit comparison walks through the decision in more detail, and the two elections can also be combined across different income types in the same year.

What Does the US-Belgium Tax Treaty Do for Double Taxation?

The United States and Belgium have a modern comprehensive income tax treaty, in force since 2007, but for most Americans on the ground in Belgium the treaty is not where the day-to-day double-tax relief comes from. Like nearly every US treaty, it contains a standard saving clause that lets the United States tax its own citizens and green card holders largely as if the treaty did not exist, so the domestic Foreign Tax Credit and Foreign Earned Income Exclusion mechanisms described above do most of the actual work of avoiding double taxation on wages.

Where the treaty matters most is in the details: tie-breaker rules for residency when someone could be considered a resident of both countries in the same year, reduced withholding on certain investment income, rules for business profits, and provisions touching pensions and other specific categories of income. Because treaty provisions have to be read in their specific text, any position relying on a specific treaty provision beyond the general saving-clause framework should be reviewed against the actual treaty language before you file.

Does the US-Belgium Totalization Agreement Cover Social Security?

Yes. A totalization agreement between the United States and Belgium has been in force since July 1, 1984, and it exists specifically to stop a worker from paying into both countries' social security systems on the same earnings at the same time. Without it, an American employee or self-employed person working in Belgium could owe both Belgian social security contributions and US self-employment tax on the identical income.

The agreement works by assigning coverage to a single system based on where the work is performed and how long the assignment is expected to last, and that assignment is documented with a certificate of coverage. Depending on the direction of the assignment, the certificate is issued by the Social Security Administration, to keep someone covered under the US system while working temporarily in Belgium, or by the Belgian social security authorities, to keep someone covered under the Belgian system. Self-employed Americans in Belgium should not assume US self-employment tax automatically applies; our guide to totalization agreements and self-employment tax abroad covers how the certificate process works. The Social Security Administration's Belgium totalization pamphlet explains the coverage rules in detail.

How Are Belgian Pensions and Retirement Accounts Taxed by the US?

Not automatically. Belgium offers several distinct retirement vehicles: the statutory state pension, employer-sponsored group insurance plans, and individual pension savings accounts opened through a Belgian bank or insurer. Being tax-favored under Belgian law does not, by itself, make any of these tax-deferred for US purposes.

US law starts from the opposite assumption Belgium does: under IRC §§401(a) and 402(b), income building up inside a foreign retirement plan is taxed to a US person as it accrues unless a specific treaty provision says otherwise. Whether the US-Belgium treaty provides that deferral, and for which type of Belgian plan, is fact-specific and has to be analyzed against the actual treaty text rather than assumed. Because the analysis is the same regardless of which country the plan is in, our foreign pension US tax treatment guide walks through the four questions that determine the answer for any foreign plan: whether growth is taxed as it accrues, whether a treaty defers it, what has to be reported, and how distributions are taxed.

Are Belgian Investment Funds Taxed as PFICs?

Usually, yes, and it catches a lot of Americans banking in Belgium off guard because nothing about the label "SICAV" signals a PFIC problem. A Belgian SICAV, whether it is a mutual fund, an actively managed fund, or many ETFs domiciled in Belgium or elsewhere in the EU, generally meets the US definition of a passive foreign investment company under IRC Section 1297, with Sections 1291 and 1298 controlling how it gets taxed. Belgium's own domestic tax treatment of the fund has no bearing on that US classification.

Absent a timely election, the default PFIC regime is expensive by design: gains and certain distributions get spread over your entire holding period, taxed at the top rate for each of those years, and stacked with an interest charge for the years you held it without paying tax on the built-up gain. Each PFIC generally requires its own Form 8621 filing, and that reporting duty applies even in a year no tax is actually owed. This is one of the clearest reasons Americans in Belgium are usually steered toward US-domiciled brokerage accounts and US-based index funds for new investing rather than opening a local SICAV or investment account through a Belgian bank.

What Else Do You Have to Report to the IRS?

The income tax return is only part of the compliance picture. Belgian bank, brokerage, and pension-related accounts trigger their own information-reporting rules on top of it, each enforced independently of whether the return itself shows any US tax owed, and the penalties for skipping them tend to dwarf whatever tax was actually at stake.

For anyone whose path to Belgium was not simple US citizenship living abroad, say a string of short-term stints in Brussels on an EU institution contract or a NATO posting before the assignment turned into a permanent move, whether you count as a US tax resident at all is its own question, answered by the substantial presence test.

Bottom Line

Belgium's combination of national tax and communal surcharge is steep enough that, for most Americans there, the Foreign Tax Credit ends up doing nearly all the double-tax work on its own, but the credit doing most of the work does not mean there is nothing else to file. FPS Finance and the IRS run on separate tracks, the treaty's saving clause limits how much relief it actually provides beyond the credit, and the totalization agreement still needs its own certificate of coverage to keep social security taxed once instead of twice. Pensions, Belgian investment funds, and foreign accounts each layer their own reporting rules on top of that income tax analysis, and because Belgium's tax bill is already high, the real risk here is not underpaying the IRS, it is missing one of those separate filings and paying a penalty for it instead.

Have questions about US expat taxes in Belgium? Contact TS CPA for a free consultation. We respond within the same day.

Official IRS and Government Sources

• IRS, Foreign Earned Income Exclusion
• IRS, Foreign Tax Credit
• IRS, US Citizens and Resident Aliens Abroad
• IRS, United States Income Tax Treaties A to Z
• Social Security Administration, US-Belgium Totalization Agreement
• FinCEN, Report of Foreign Bank and Financial Accounts (FBAR)
• IRS, About Form 8621
• IRC Section 911, Citizens or Residents Living Abroad