Written for Mexico. This analysis applies to Mexican federal tax law — ISR (income tax), IVA (VAT) and SAT rules — and cites Mexican statutes. Amounts are in Mexican pesos (MXN).
Every investor in CETES or bank promissory notes knows the withholding — and almost no one understands what it is. Let's clear up the most expensive misunderstanding for conservative savers: the withholding (0.90% per year on the principal invested as of 2026 — the LIF raised it from 0.50%, DOF 7-nov-2025) is not your tax: it is a prepayment on account. Your actual tax is computed in the annual return, on the real interest, at your rate — and that calculation can end with you paying, at zero, or with a refund.
The mechanics in three pieces
Piece 1 — the withholding: financial institutions withhold an annual percentage on the principal balance (not on the interest): MXN $1M invested through all of 2026 incurs ~$9,000 of withholding, whatever it earns. It is prepaid cash flow, creditable to the last centavo. Piece 2 — real interest: what is taxable is the interest that exceeds inflation for the period (art. 134 LISR): with CETES at ~8% and inflation at ~4%, only half of your return is the taxable base — the inflationary half is a replacement of purchasing power, not a gain (illustrative rates; your statement carries the exact calculation). Piece 3 — the annual return: you add the real interest to your other income, compute the tax at your rate, and credit what was withheld. Corollaries: the high-rate taxpayer usually owes the difference; the low-income one, or the one with small real interest, frequently has a credit balance that only those who file the annual return recover — millions of savers give away that refund every year by not filing.
The rules of the game worth knowing
There is an obligation to file the annual return for interest in specific cases (real interest above a threshold, or interest together with other income above certain amounts — check your case; the threshold box changes little but decides penalties). The tax statements that each institution issues in January–February are your master input: nominal interest, real interest, withholding — always download and archive them (and compare them against the SAT's pre-filled return, which sometimes duplicates or mixes accounts: the pre-filled return is corrected, not worshipped). In joint accounts, the interest belongs to the account holders in the agreed proportion or in equal parts — another silent lever: the ownership of family investments distributes the burden across different rates (a spouse with no other income = real interest with almost no tax and the withholding refunded). And the loss when inflation exceeds interest (negative real interest) is creditable/deductible under the rules — the bad year is also filed, because it leaves a credit.
Is your conservative portfolio paying the correct tax — or the convenient one?
The annual review of a fixed-income portfolio takes an hour and usually finds money: unrecovered withholdings, suboptimal ownership, pre-filled returns with errors, and the comparison against alternatives (debt funds, bonds through a brokerage, UDIBONOS with their natural inflation treatment) that, at your rate, change the real net return. The gross is set by the market; the net is set by the structure.
Frequently asked questions
Does CETES Directo withhold the same as a bank?
Yes — the mechanics of withholding on principal and the annual statement work the same. CETES Directo's advantage is cost (no fees), not tax. And the same universal advice applies: download your statement every January and file — especially if your rate is low, because that is where your refund lives.
Do UDIBONOS pay less tax?
Conceptually, their inflationary component is protected by design (the principal is adjusted in UDIs) and what is taxable is the real coupon — aligned with the real-interest principle. For long horizons and high marginal rates, the after-tax comparison of a UDIBONO versus a nominal instrument is less obvious than it looks: you run the numbers.
What about interest from SOFIPOs and lending platforms?
Same principle (real interest added to your income, withholding as a prepayment) with nuances by type of institution — and a non-tax warning that matters more: the rate spread over CETES is a risk premium, not a gift. For tax purposes they are interest; financially they are a different asset class.
Can I 'avoid' the withholding by investing in my minor child's name?
The returns on a minor's assets are generally attributed to whoever holds parental authority — the family 'name loan' does not shift the burden and does manufacture source-of-funds and ownership problems. The legal version of the idea is the REAL distribution of wealth among members with different rates — documented transfers, not nameplates.
Let's talk about your case
The first step is always the same: an honest diagnostic of where you stand. Write to us on WhatsApp or call — a reply the same business day.