For a US investor, Mexican Treasury bonds and US tax rules interact on three fronts: Mexico withholds a small percentage of each interest payment at source, the IRS taxes that same interest as worldwide income while allowing a credit for what Mexico took, and any gain or loss from peso movements over your holding period is taxed separately as ordinary income under Section 988. On top of the tax itself, holding these bonds in a Mexican account almost always triggers FBAR and FATCA reporting, both of which carry heavy penalties if missed.
Mexican Withholding on Interest
Mexico taxes interest paid to non-residents at source. For interest on publicly traded Mexican government debt, the standard withholding rate is 4.9%. Your custodian or paying agent deducts it automatically before the coupon reaches your account, so you never see the gross amount.
The US-Mexico income tax convention sets maximum withholding rates on cross-border interest that are generally more favorable than Mexico’s domestic statutory rates.1Internal Revenue Service. United States – Mexico Income Tax Convention2U.S. Department of the Treasury. Technical Explanation of the Protocol Between the United States and Mexico To get the reduced treaty rate, you need to give the Mexican financial intermediary holding your bonds your US taxpayer identification number and file a declaration with them. Skip that step and the custodian applies the full domestic rate, and you’ll be chasing a refund from Mexico’s tax authority rather than the IRS.
US Tax on the Interest
US persons owe federal income tax on worldwide income, so every peso of interest from a Mexican bond is taxable on your US return regardless of what Mexico already withheld. You convert each interest payment from pesos to dollars using the exchange rate on the date you received it, and that dollar amount is what goes on your return as interest income.
To avoid paying full tax to both countries on the same money, you claim a Foreign Tax Credit for the Mexican withholding. If your total creditable foreign taxes for the year are $300 or less ($600 on a joint return) and all your foreign income is passive, you can take the credit directly on your return without filing Form 1116. Above those thresholds, or if any of the foreign income is non-passive, Form 1116 is required.3Internal Revenue Service. Instructions for Form 1116 (2025) The credit is limited to the US tax that would otherwise apply to that foreign income, so if your marginal US rate is well above 4.9%, the credit offsets the Mexican tax fully and you still owe US tax on the remainder.
Currency Gains Are Ordinary Income
This is the piece that catches investors off guard. A peso-denominated bond is a foreign currency position as well as a debt instrument, and the peso side of that position gets its own tax treatment.
Under Section 988 of the Internal Revenue Code, acquiring a debt instrument denominated in a foreign currency is a covered transaction, and any gain or loss attributable to the currency movement over your holding period is treated as ordinary income or ordinary loss.4Office of the Law Revision Counsel. 26 U.S. Code 988 – Treatment of Certain Foreign Currency Transactions Not capital gain. It doesn’t matter how many years you held the bond; long-term capital gains rates never apply to this piece.
You compute it separately from interest. Take the dollar value of your peso investment on the day you bought the bond, compare it to the dollar value of the pesos you receive at maturity or sale, and the difference is your Section 988 gain or loss. If the peso appreciated against the dollar during your holding period, you have an ordinary gain on top of the interest income you already reported. If the peso weakened, you have an ordinary loss. Because these bonds are peso-denominated, this calculation is unavoidable on every position, not something you can plan around.
FBAR: FinCEN Form 114
If the aggregate value of all your foreign financial accounts exceeds $10,000 at any point during the calendar year, you must file a Report of Foreign Bank and Financial Accounts.5FinCEN.gov. Report Foreign Bank and Financial Accounts A brokerage or custodial account in Mexico holding your bonds counts, and the $10,000 threshold is aggregate across every foreign account you hold, not per account.
The FBAR is filed electronically with FinCEN, not the IRS. The due date is April 15, with an automatic extension to October 15 that requires no separate request.6FinCEN.gov. Due Date for FBARs The penalty for non-willful failure to file can reach $10,000 per report, and willful violations carry far steeper consequences. Investors trip over this because they think of a Mexican bond account as an investment rather than a foreign financial account. It’s both.
FATCA: Form 8938
Form 8938 is a separate report of specified foreign financial assets, filed with your tax return under the Foreign Account Tax Compliance Act. The thresholds depend on your filing status and where you live:
- Single filers living in the US: $50,000 on the last day of the year or $75,000 at any time during the year
- Joint filers living in the US: $100,000 year-end or $150,000 at any time
- Single filers living abroad: $200,000 year-end or $300,000 at any time
- Joint filers living abroad: $400,000 year-end or $600,000 at any time
These are the levels above which Form 8938 becomes mandatory.7Internal Revenue Service. Summary of FATCA Reporting for U.S. Taxpayers FBAR and FATCA overlap in what they cover, and you may well need to file both for the same Mexican account. They go to different agencies and follow different rules, so filing one does not satisfy the other.
When These Rules Don’t Apply
If your exposure to Mexican government bonds comes through a US-listed ETF or mutual fund rather than a direct account in Mexico, the foreign account reporting requirements generally don’t reach you. The account is held at a US institution, and the fund itself carries the reporting burden. You still owe US tax on the fund’s distributions in the normal way, but FBAR and Form 8938 typically stay off your desk. Direct holdings through a Mexican brokerage or custodial account are a different matter, and every rule above applies in full.