Mexico Tax Guide for US Expats: SAT Filing, the 183-Day Rule and Dual Obligations

Mexico Tax Guide for US Expats: SAT Filing, the 183-Day Rule and Dual Obligations

Mexico's tax obligations and your continuing US obligations interact in specific ways that most expats don't fully understand until something goes wrong. This guide covers the key rules, the 183-day threshold, how the US-Mexico tax treaty functions, and when you need professional help — clearly and without the confusion that most generic expat tax content produces.

The US Side: You Still Owe US Taxes — Always

The United States taxes its citizens and permanent residents on worldwide income regardless of where they live. Moving to Mexico does not reduce, defer, or eliminate your US federal income tax obligation. You continue filing a US federal tax return each year, disclosing all income from all sources globally. This is not optional and the penalties for non-compliance are significant (FBAR penalties alone can reach $10,000 per unreported account per year for willful violations).

Foreign Earned Income Exclusion (FEIE)

If you have earned income (wages, self-employment income) from working abroad, the FEIE allows you to exclude up to approximately $126,500 (2024 base, indexed annually for inflation) from US federal income tax. To qualify, you must meet either the Bona Fide Residence Test (established resident in a foreign country for a full calendar year) or the Physical Presence Test (330+ days in a foreign country within a 12-month period). Social Security, pension, 401k distributions, and investment income are NOT earned income and cannot be excluded via FEIE.

Foreign Tax Credit (FTC)

The Foreign Tax Credit allows you to offset US tax with income taxes paid to Mexico. If you pay Mexican income tax on income that's also potentially taxable in the US, the FTC prevents true double taxation in most circumstances. The FTC is often more beneficial than the FEIE for retirees with investment and distribution income.

The Mexico Side: The 183-Day Rule

Spending more than 183 days in Mexico in a calendar year triggers Mexican tax residency — Mexico's right to tax your worldwide income under ISR (Impuesto Sobre la Renta). The count is cumulative across the calendar year, not consecutive: 100 days in spring plus 90 days in fall equals 190 days total and triggers residency that year.

Mexican tax residents must file an annual declaracion anual with SAT (typically due April 30 for the prior calendar year). Mexican income tax rates are progressive, reaching 35% at the top bracket (income above approximately 3 million pesos annually). For US retirees with Social Security and modest investment income, Mexican income tax obligations are often limited by treaty provisions — but the filing obligation exists regardless.

The US-Mexico Tax Treaty: How It Actually Works

The US and Mexico have a comprehensive tax treaty that prevents double taxation in most scenarios. Key provisions relevant to expats:

• Income taxed in Mexico generally generates a Foreign Tax Credit against US tax — the treaty prevents paying full tax in both countries

• Social Security benefits: under the treaty, US Social Security is typically taxed only by the country of the recipient's residence; if you are a Mexican tax resident, Mexico has the right to tax your Social Security under treaty interpretation (though the US also has the right to tax it — consult a treaty specialist for your specific situation)

• Pension income: generally taxable in the country of residence

• Capital gains: generally taxable in the country of residence for most assets

• The treaty does NOT eliminate the obligation to file in both countries — it prevents double taxation, not double filing

Practical Scenarios

Retiree Under 183 Days (Part-Year Mexico)

If you spend fewer than 183 days in Mexico per calendar year, you are not a Mexican tax resident. No Mexican filing obligation. Continue US filing as normal. The Foreign Earned Income Exclusion generally doesn't apply to retirement income, but FEIE may apply if you have any active foreign work income.

Retiree Over 183 Days (Full-Year Mexico)

Mexican tax residency triggered. Annual declaracion anual required with SAT. Apply Foreign Tax Credit to offset US tax with any Mexican taxes paid. For most retirees with Social Security and modest investment income, the treaty and FTC structure means actual double-taxation is limited — but the dual filing obligation is real and requires a professional who knows both systems.

Remote Worker With Mexican-Source Income

Working for a Mexican company or earning income from Mexican clients triggers SAT registration, RFC requirements, and monthly and annual filing obligations in Mexico. CFDI invoicing compliance is required for business income. These are separate obligations from the 183-day rule and exist regardless of how many days you spend in Mexico.

SAT Registration and Filing Practically

If you have Mexican-source income or have triggered the 183-day threshold: get your RFC (required — the SAT registration process). File monthly declarations if you have active income (declaraciones provisionales). File the annual declaracion anual by April 30 of the following year. Late filing generates multas (fines) and recargos (interest) that accumulate monthly. SAT's electronic systems have improved significantly — but navigating them correctly the first time requires either a very patient self-study or a contador.

When You Absolutely Need a Tax Professional

• You expect to spend more than 183 days in Mexico in any year

• You have any Mexican-source income (rent, employment, business, services to Mexican clients)

• You plan to sell property in Mexico (the notario handles withholding but you need to understand the full picture)

• You have FBAR/FATCA filing obligations — Mexican bank accounts over $10,000 must be reported to FinCEN annually

• You are starting a Mexican business or employing Mexican workers

Paul refers consulting clients to contadores who specialize in foreign residents — not general Mexican tax practitioners who may not understand the US side of the equation. Ask for this referral in any consulting session.

Free Tools

Mexico Reality Check ($99) — includes your specific tax situation assessment: mymexicomove.com/booking-calendar | Master Guide ($47): mymexicomove.com/shop | paul@mymexicomove.com