How to become tax-compliant in Mexico if you have not filed SAT returns for years

Time does not erase the debt: how what you owe grows every month

One of the most expensive beliefs among those who have not filed for a long time is that "if they have not said anything, maybe I do not owe anything" or that time passes and the situation fades. The real mechanism is the opposite: each month that passes without regularizing, the debt grows through three simultaneous channels.

The first is inflation adjustment. Article 17-A of the Federal Tax Code (CFF) requires updating unpaid taxes by multiplying them by the ratio of the INPC for the month of payment to the INPC for the month the tax was due. With Mexico's accumulated inflation over the last three years, a $100,000 MXN debt from 2022 is already worth close to $120,000–$125,000 MXN adjusted to 2026 before touching surcharges.

The second is surcharges under article 21 CFF: 1.47% monthly on the inflation-adjusted tax. Over three years, surcharges alone represent approximately 53% additional on the original debt (1.47% × 36 months).

The third is fines for not filing declarations and for not paying. Article 82 CFF sets fines from $1,810 to $44,790 MXN per unfiled return, and fines of 55% to 75% of the omitted tax for non-payment (Art. 76 CFF).

An $80,000 MXN ISR debt from 2022 can cost $228,000 MXN by 2026 if not regularized. That is without counting additional fiscal years or VAT. The argument that "it is better to wait" has no numerical basis.

How long SAT has to collect: the 5-year limit and when it becomes 10

Article 67 CFF establishes that SAT's powers to determine unpaid taxes expire in five years, counted from when the return was filed or should have been filed. However, the limit extends to ten years when the taxpayer never registered in the RFC while required to do so, or when they kept no accounting or kept it with omissions that make it impossible to determine obligations. In practice, most cases of people who "have not filed for a long time" fall into one of those categories — meaning the real window is 10 years, not 5.

The three most common situations

Situation 1: I had income but never registered for RFC

Freelancers, independent contractors, landlords or anyone who received income in Mexico without an active RFC. Regularizing involves two steps: registering the RFC retroactively with the real start date of activities, then filing all pending returns using documented real income. If income documentation is incomplete, SAT can make a presumptive determination — which is always more expensive than what the taxpayer would have paid using their own data.

Situation 2: I had an RFC, filed for a while, then stopped

The most common situation. The RFC remains active, obligations keep running, but returns stopped being filed. SAT has the RFC on record and can see the last declared figures. The regularization process is the same regardless of whether the unfiled years had income or not: file all late returns, calculate the correct tax and pay with the corresponding accessories.

Situation 3: I left Mexico and never deregistered my RFC

Very common among foreigners and Mexican emigrants. The RFC stays active with running obligations, the tax mailbox accumulates notifications nobody reads, and upon returning — or trying to do any tax procedure — a debt appears representing years of fines and surcharges for unfiled returns. If income during that period was earned abroad and does not constitute Mexican-source income, those years may be declarable as zero activity — but this needs to be supported, not simply assumed. Our guide on tax residency in Mexico for foreigners explains when foreign income becomes taxable in Mexico.

The step-by-step regularization process

Step 1 — Diagnose: what SAT knows about you
Before any action, log into the SAT portal with your RFC and password (or e.firma) and review: which returns you have filed, what differences SAT has recorded between what you declared and what third parties reported, and whether there are already determined tax credits. This diagnosis defines the real size of the problem.

Step 2 — Reconstruct your actual income
Gather all income documentation for the pending fiscal years: bank statements, contracts, CFDIs issued, platform records (Airbnb, Uber, Mercado Libre), international transfers received. What you cannot document, SAT can estimate using third-party information — and their estimate is always conservative for them and expensive for you.

Step 3 — File the late returns
Returns can be filed at any time, even years late. The SAT system accepts them and automatically calculates the inflation adjustment and surcharges at the time of filing. File them chronologically from oldest to newest.

Step 4 — Pay or negotiate
Once returns are filed, the system generates the payment reference line. Payment can be made in a single installment, in up to 12 monthly installments (Art. 66 CFF, with a formal request to SAT), or through an installment agreement when the total is unmanageable.

RFC suspended vs. RFC active with unfiled returns: not the same thing

A common confusion is between having informally "stopped activity" and having formally filed a suspension-of-activities notice with SAT. An RFC with a formal suspension notice on file has no obligation to file monthly VAT returns or ISR provisional payments during the suspended period. An active RFC with no returns filed has running obligations that SAT records as uncomplied — with fines and surcharges accumulating. If you genuinely had no income during the unfiled years, the cleanest path is to file zero-income returns for those periods and formally request suspension of activities retroactively, then activate again from when real activity resumed.

Real case: the entrepreneur who ignored three years of tax mailbox notifications

A Mexican graphic designer with an active PFAE RFC since 2019 had two good income years (2020 and 2021) but never filed annual returns or monthly VAT declarations. In 2022 activity slowed and in 2023 he temporarily moved to Spain. He returned in 2025 intending to incorporate an SA de CV with a partner, and when trying to obtain the corporate e.firma discovered his personal RFC had restrictions for non-compliance.

Our diagnosis revealed: four unfiled annual returns (2020–2023), 48 unfiled monthly VAT declarations, and an already-determined tax credit of $187,000 MXN from SAT for 2020–2021 (SAT had estimated his income based on the CFDIs his clients issued him as an expense). The real debt with adjustment and surcharges at the time of diagnosis was $312,000 MXN.

The strategy was to file all late returns with the real documented income (which was lower than SAT's estimate for 2021 because not all income had gone through CFDIs), reducing the tax base. For 2022 and 2023 income had been minimal, so those returns resulted in small amounts. The final total with accessories was $198,000 MXN — less than SAT's presumptive determination — paid in 12 installments. The RFC restriction was lifted as soon as all pending returns were filed.

What cost the most was not the tax but the time: the process took four months from diagnosis to a clean RFC. The SA de CV was incorporated five months later than originally planned. For context on the fines structure we navigated, our guide on SAT fines in Mexico has the full table of current amounts.

How to check your tax situation today

• Log into sat.gob.mx → "Trámites y servicios" → "Declaraciones" → "Consulta tus declaraciones presentadas". Check which fiscal years and months are covered.
• Check your tax mailbox — if there are letters, requirements or already-issued tax credits, you need to act immediately.
• In "Mi contabilidad", check if SAT has recorded differences between what you declared and what third parties reported.
• Verify your RFC status in "Consulta RFC" — restrictions or an unactivated tax mailbox both require attention.

With that diagnosis in hand, you have the full picture of the problem. What does not help is acting on the past without knowing the full map — filing returns blindly without knowing whether SAT already has third-party data can create inconsistencies that complicate more than they resolve. And once you are compliant, review our guide on filing your annual SAT return to stay current going forward.