Selling shares for more than you paid generates a capital gain (plusvalía). In Mexico, you would not owe ISR until you sell. And when you do sell, Mexican law offers a significant advantage if you use the right system.
The 10% definitive rate rule:
- If you sell shares or ETFs through a licensed Mexican stock exchange (BMV or BIVA), the gain would be taxed at a fixed, definitive rate of 10%.
- This rate would not be pooled with your acumulables — it would not push you into a higher salary bracket.
- The SIC (Sistema Internacional de Cotizaciones): This is the flagship tool. The SIC allows Mexicans to buy foreign shares (such as Apple, Tesla, or ETFs like VOO) through a Mexican broker. Because they are traded through the SIC, they would also benefit from the 10% rate!
The foreign-broker trap: If you open an account with a US broker (e.g. TD Ameritrade, Interactive Brokers) and sell shares there, that gain does NOT pass through a Mexican exchange. Therefore it would lose the 10% benefit. You would need to add the gain to your acumulables and could be taxed at up to 35%. That is why regulated Mexican brokers (GBM, Bursanet) would be fiscally superior for the small investor.
Losses: If you sell shares at a loss via the SIC/BMV, you could use that loss to reduce your stock-market gains (subject to the 10%) in that year or over the following 10 years.