Marriage feels personal. Tax law, less so. Yet when you’re a US citizen married to someone who isn’t, those two worlds overlap in ways that can be surprisingly technical.
The United States taxes its citizens on worldwide income. Your spouse’s citizenship or lack of it doesn’t change your obligation. What it does change is how you file, what income gets reported, and whether you expose your spouse’s finances to the US tax system.
Let’s walk through it calmly.
What Is a Nonresident Alien Spouse?
If your spouse is not a US citizen and does not hold a green card or meet the substantial presence test, the Internal Revenue Service generally treats them as a nonresident alien (NRA) for tax purposes.
That label is purely tax-based. Your spouse might have lived in France their entire life, earned only French income, and never set foot in the US, and for US tax purposes, they’re an NRA.
That classification shapes your filing options.
Option One: Married Filing Separately (The Default)
If you’re married to a nonresident alien, the default position is simple: you file Married Filing Separately (MFS).
In this scenario:
You report your worldwide income.
Your spouse does not file a US return unless they have US-source income.
Your spouse’s foreign salary, investments, and savings stay outside the US tax system.
For many expats, this feels safer. If your spouse earns €120,000 in Germany and has multiple local investment accounts, keeping that entirely outside US reporting can be attractive.
However, filing separately comes with trade-offs. Certain tax credits are reduced or unavailable. Tax brackets can be less favorable. In some cases, the overall tax bill is higher.
Sometimes the simplicity is worth it. Sometimes it isn’t.
Option Two: Elect to Treat Your Spouse as a US Resident
Under Internal Revenue Code §6013(g) or (h), you can choose to treat your nonresident alien spouse as a US tax resident and file Married Filing Jointly.
That election changes everything.
Once made:
You file a joint return.
Both spouses’ worldwide income becomes reportable.
Both spouses must include global wages, interest, dividends, and business income.
Why would anyone do this?
Because joint filing often comes with lower tax brackets and access to credits that aren’t available when filing separately. For example, if your spouse earns modest income abroad and you qualify for the Foreign Earned Income Exclusion or Foreign Tax Credits, joint filing can sometimes produce a lower combined tax result.
But there’s a catch. Actually, several.
If you make this election, your spouse’s foreign bank accounts may become reportable under FBAR rules if thresholds are met. FATCA reporting (Form 8938) thresholds also change when filing jointly. Suddenly, accounts that were previously invisible to the US system may require disclosure.
It’s not just about income. It’s about exposure.
How It Affects Foreign Income
Suppose you live in Singapore. You earn $150,000 from your US employer. Your spouse earns $40,000 locally.
If you file separately, only your $150,000 is reported on your US return. You might claim the Foreign Earned Income Exclusion or Foreign Tax Credits on your portion.
If you elect joint filing, both incomes are reported. The total household income becomes part of the US calculation. Credits may offset some or all US tax, but the compliance footprint expands.
There isn’t a universally “correct” choice. It depends on income levels, local tax rates, asset size, and long-term planning.
Gifts and Financial Transfers
Marriage doesn’t eliminate all tax considerations between spouses.
For 2025, transfers from a US citizen to a nonresident alien spouse are subject to a higher annual gift exclusion than the standard annual gift exclusion but it’s not unlimited. Large transfers beyond that annual threshold can require reporting.
That nuance rarely comes up in casual conversation, yet it matters for couples moving significant assets across borders.
Children and Credits
If you have children, filing status influences access to certain credits. Filing jointly may open eligibility for benefits that Married Filing Separately restricts.
However, joint filing also brings your spouse fully into the US tax system for that year and potentially beyond, depending on how long the election remains in effect.
That’s the balance.
Thinking Through the Trade-Offs
Some couples prefer clean separation: one spouse in the US system, the other outside it. Others prefer consolidation, especially when the math favors joint filing.
Neither approach is inherently better. What matters is understanding the consequences before checking the box.
Need Help Reviewing Your Filing Options?
If you’re married to a non-US spouse and want clarity on whether to file separately or make a joint election for the 2025 tax year, Expat US Tax works specifically with mixed-nationality couples navigating cross-border reporting and compliance.