The 183-day mistake most articles keep repeating
The most widespread misconception among expats arriving in Mexico is believing that living there for more than 183 days automatically makes them Mexican tax residents. This is incorrect.
In Mexico, 183 days is the threshold under Article 154 of the LISR, which governs the taxation of non-residents physically working in Mexico for a foreign employer. Under that rule, if a non-resident works physically in Mexico for a company domiciled abroad, their employment income starts being taxed in Mexico from day 184 of their presence in the country.
Mexican tax residency is triggered through a completely different mechanism, regulated by Article 9 of the CFF:
- Route 1 (most common): If you establish a permanent home in Mexico and have no permanent home in any other country, you are a Mexican tax resident from day one — regardless of how many days you have spent there.
- Route 2: If you have a home in Mexico and also in another country, you are a Mexican tax resident only if your center of vital interests is in Mexico. This occurs when more than 50% of your annual income comes from Mexican sources, or your principal professional activity takes place in Mexico.
The distinction matters because fiscal obligations in Mexico are completely different for residents and non-residents. A tax resident will be taxed on their worldwide income in Mexico. A non-resident is only taxed on Mexican-source income, with withholding at source.
Mexico-US treaty: what it solves and the clause most people miss
The Convention between the United States of America and the United Mexican States to Avoid Double Taxation was signed in Washington on September 18, 1992 and has been in force since January 1, 1994. It remains the most relevant treaty for the estimated 1.5 million US citizens living in Mexico.
Maximum withholding rates established by the treaty for income flows between the two countries:
| Income type | Without treaty | With Mexico-US treaty | Article |
|---|---|---|---|
| Dividends (>10% holding) | Up to 30% | 5% | Art. 10 |
| Dividends (others) | Up to 30% | 10% | Art. 10 |
| Interest (bank or financial company) | Up to 30% | 4.9% | Art. 11 |
| Interest (others) | Up to 30% | 10% | Art. 11 |
| Royalties / digital royalties | Up to 30% | 10% | Art. 12 |
| Government pensions | Full taxation | Partial exemption | Art. 19-20 |
However, there is a point that generic articles about the Mexico-US treaty almost never explain: the saving clause in Article 1(3).
This clause states that the US reserves the right to tax its citizens and permanent residents as if the Treaty did not exist. In practice, this means a US citizen in Mexico:
- Remains required to file a US federal return (Form 1040) every year
- Remains subject to US federal income tax on worldwide income
- Can use the Foreign Tax Credit (Form 1116) to credit ISR paid to SAT, reducing the final US tax burden
- Can use the FEIE (Foreign Earned Income Exclusion, up to $132,900 in 2026) to exclude employment income earned in Mexico
The treaty is useful for reducing withholding at source (the percentages in the table above) and for avoiding double taxation on dividends, interest and royalties. But it does not exempt US citizens from their reporting and filing obligations in that country.
Mexico-Spain treaty: the 2015 Protocol that changed information-sharing rules
The Mexico-Spain Treaty was also signed in 1992 and entered into force in 1994. Unlike the US treaty, Spain has no equivalent saving clause: Spanish tax residents who become Mexican tax residents stop being taxed in Spain on their employment income earned in Mexico.
Main withholding rates under the Mexico-Spain treaty:
| Income type | Without treaty | With Mexico-Spain treaty | Article |
|---|---|---|---|
| Dividends (>25% holding) | Up to 30% | 5% | Art. 10 |
| Dividends (others) | Up to 30% | 15% | Art. 10 |
| Interest (financial institution) | Up to 30% | 4.9% | Art. 11 |
| Interest (others) | Up to 30% | 10% | Art. 11 |
| Royalties | Up to 30% | 10% | Art. 12 |
| Real estate income | 25% ISR withholding | Taxed where property is located | Art. 6 |
The 2015 amending Protocol (in force since July 2017) primarily updated information-sharing mechanisms between SAT and the Spanish Tax Agency. This has practical consequences: both administrations can request and share taxpayer fiscal data, including returns, bank balances and corporate structures. A Spanish person in Mexico who has not notified the Spanish Tax Agency of their change in tax residency may receive information requests from both Spain and Mexico.
Mexico-Russia treaty (2004): in force, but a trap for those with US ties
The Agreement between the Government of the Russian Federation and the Government of the United Mexican States to Avoid Double Taxation on Income Taxes was signed June 7, 2004 and remains fully in force in 2026. For Russian citizens who are tax residents of Mexico, the treaty establishes: dividends from Russian companies, maximum 10% withholding in Russia; interest from Russian sources, maximum 10%; royalties from Russian sources, maximum 10%; real estate income taxed where the property is located.
The complication arises for Russian citizens who also have assets, income or structures in the United States. Since August 2024, Russia has partially suspended its double taxation treaty with the US. The result is that income flows between Russia and the US — dividends, interest, royalties — may face maximum withholding rates from both sides without treaty benefit.
The Russia-Mexico treaty is not affected by this suspension. But a Russian citizen with income from all three jurisdictions (Russia, Mexico, USA) needs a tripartite tax analysis: the Russia-Mexico treaty for bilateral flows, and planning without treaty benefits for Russia-US flows.
Tiebreaker rules when you are a tax resident in two countries simultaneously
The most common case with expats: you have established residency in Mexico but still have your home, family or main business in your home country. Both countries claim you as a tax resident. The treaty resolves this through the tiebreaker rules of Article 4, applied in this strict order:
- Permanent home: You are a resident of the country where you have a permanent home available. If you have a permanent home in both countries → next criterion.
- Center of vital interests: You are a resident of the country with which you have the closest personal and economic relations (family, work, main assets). If this cannot be determined → next.
- Habitual abode: You are a resident of the country where you habitually reside. If both equally or neither → next.
- Nationality: You are a resident of the country whose nationality you hold. If both or neither → next.
- Mutual agreement: The tax authorities of both countries resolve by mutual agreement.
What no treaty resolves: the missing Totalization Agreement between Mexico and the US
Double taxation treaties apply to income taxes (ISR, federal income tax). They do not apply to social security contributions. Totalization Agreements serve that purpose, allowing contributions in one country to count toward pension rights in the other.
Mexico has Totalization Agreements with Spain, Canada, Japan, Korea, Australia and other countries. It does not have a Totalization Agreement with the United States. This means a self-employed US citizen in Mexico may be required to contribute to both systems simultaneously: US Self-Employment Tax of 15.3% on the first $160,200 USD of net self-employment income (2026), plus IMSS contributions in Mexico if they have a registered business activity there.
Negotiations for a Mexico-US Totalization Agreement have been ongoing for years without conclusion. No clear timeline exists for its signing.
When the treaty exists but does not protect you: the three most common scenarios
Having a treaty does not guarantee protection. These are the cases where the treaty exists but the expat still faces double taxation:
- US citizens in any country: The saving clause (Art. 1(3) of the US-Mexico treaty) maintains the obligation to file and pay US taxes on worldwide income, although the FTC reduces the real impact.
- Non-tax-residents in Mexico: If you do not meet the conditions for Mexican tax residency, the treaty only applies in the opposite direction. You cannot use the Mexico-X treaty to reduce withholding if SAT does not consider you a Mexican tax resident.
- Mixed structures without planning: If you have dividend income in Spain, real estate income in Russia and employment income in Mexico, each flow is governed by the treaty applicable to that pair of countries. Without a properly documented structure, treaty benefits must be actively claimed — they are not applied automatically.
International tax planning requires identifying your actual tax residency, classifying each income type under the articles of the applicable treaty, and documenting the application of treaty benefits with both countries' tax authorities. Nexoconsult works with US, Spanish, Russian and other nationals in Mexico — view available plans here.