Taxes on US Stocks and ETFs from Mexico: SAT, W-8BEN and the 30% (2026)

If you are a Mexican investor buying US stocks or ETFs, the tax question is the one that keeps people up at night: am I going to get taxed twice? The short answer is reassuring. Two countries can touch your money, but they tax different things, and Mexico lets you subtract most of what the US already took. This guide walks through exactly who charges what, when, and how - verified as of 2026. Tax rules change and every situation is different, so treat this as education and confirm your own case with an accountant or the SAT.

When a Mexican resident invests in US shares or ETFs, two tax authorities are involved, but their roles barely overlap. The United States only taxes your dividends, through a withholding at the source: 30% by default, dropping to 10% once you file a W-8BEN. The US does not tax your capital gain when you sell. Mexico's tax authority, the SAT, does the opposite: it taxes your capital gain when you sell, and it also taxes your dividends - but it lets you credit the tax already paid in the US so you are not billed twice for the same income.

Keep that split in your head - US taxes dividends, Mexico taxes your gain and reconciles the dividends - and the rest of this guide is just the details.

The W-8BEN is a one-page IRS form, formally the "Certificate of Foreign Status of Beneficial Owner." By signing it you certify to your broker that you are not a US person and that you live in a country - Mexico - that has a tax treaty with the United States. That certification is what unlocks the treaty rate.

Without a valid W-8BEN, US law requires the broker to withhold 30% of your gross US dividends before the money ever reaches you. With the form on file, that withholding on dividends drops to the 10% treaty rate for Mexican residents. Note that the 10% is the rate for an individual portfolio investor - the lower 5% and 0% figures you may see in the treaty apply to corporate shareholders, not to a retail investor, so ignore them here.

One detail that trips people up: the form for an individual is the W-8BEN. The similarly-named W-8BEN-E is for entities (companies), not for you. A W-8BEN stays valid from the date you sign it through the end of the third following calendar year - so one signed at any point in 2026 expires on 31 December 2029, after which your broker asks you to renew it. In practice, the brokers that serve Mexican clients collect it when you open the account and apply the 10% automatically, so many investors never think about it again until renewal.

No. As a nonresident, you do not pay US tax on the capital gain when you sell US stocks or ETFs. The US taxes nonresidents on US dividends, but not on the gain from selling securities. There is a narrow exception that almost never applies to a retail investor - being physically present in the US for 183 days or more in the year - but for someone living in Mexico and investing online, the sale itself is simply not a US taxable event.

That is the good news and the catch at the same time. Because the US steps back on your gain, the gain becomes entirely Mexico's business. How Mexico taxes it depends on one thing above all: where you invested.

There are two ways a Mexican investor typically buys US assets, and they lead to very different tax lives. A Mexican brokerage (casa de bolsa) such as GBM, Kuspit or Actinver calculates and withholds your income tax (ISR) for you and issues a tax certificate (constancia). A foreign broker such as Interactive Brokers withholds nothing on your gain and issues no Mexican certificate - which means you are responsible for declaring everything yourself in the annual return. This is not a recommendation of any broker; it is simply how the two setups differ.

With a foreign broker there is an extra wrinkle worth knowing before it surprises you at tax time: you have to convert every transaction into pesos yourself, using the Banxico FIX exchange rate for the relevant dates. Because the peso-dollar rate moves, your Mexican taxable base can include a foreign-exchange gain on top of the asset's gain - the dollars themselves may have appreciated against the peso between purchase and sale. It is a real part of the calculation; how much it matters depends entirely on the currency move, so do not treat it as a fixed add-on.

Under Article 129 of Mexico's Income Tax Law (LISR), an individual pays a flat, definitive 10% on the net annual gain from selling shares on a recognized exchange, including foreign shares. The SAT has clarified (Criterio 37/ISR/N) that this 10% also reaches US shares and ETFs listed in the SIC - the Sistema Internacional de Cotizaciones, the international quotation board of the Mexican exchange - even when the sale is executed through a non-Mexican intermediary. If your US paper trades through the SIC, the 10% treatment is on solid ground.

Dividends from US companies are taxable in Mexico and go into your annual return. The relief that stops double taxation is the foreign tax credit under Article 5 of the LISR: the ISR already withheld in the US - that 10% - is creditable against the Mexican tax on the same dividend income, capped at what Mexico would have charged. In plain terms, the 10% you already paid to the US reduces what you owe the SAT on those dividends. It is not a second full tax on top; it is a reconciliation.

Individuals file the annual return (Declaración Anual) in April of the following year - so income earned during 2025 is declared by 30 April 2026. Foreign income, meaning gains and dividends earned through a foreign broker, is consolidated once a year in that return, not reported monthly.

None of this is exotic once you have done it once, but the first foreign-broker return is where an accountant earns their fee - especially on the SIC-versus-progressive question and the currency conversion. Verified as of 2026; confirm the current deadlines and rules with the SAT.

By default, yes - US law withholds 30% of gross US dividends paid to a nonresident. File a W-8BEN with your broker and that drops to the 10% treaty rate for Mexican residents.

No. A nonresident does not pay US tax on the capital gain from selling US stocks or ETFs. The gain is Mexico's matter, not the United States'.

It is - by Mexico. If the security qualifies (for example, it is listed in the SIC), the gain is generally taxed at the definitive 10% of Article 129. If it does not qualify and you sold through a foreign broker, it may be taxed at the progressive rate instead - check with an accountant.

No. The 10% already withheld in the US is creditable in Mexico under Article 5 of the LISR, so it reduces the Mexican tax on those same dividends rather than stacking on top.

Once a year, in the annual return filed in April, converting your figures to pesos with the Banxico FIX rate. Keep your own records because a foreign broker does not report to the SAT for you.