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).
"The SAT can only audit 5 years back" is one of the most repeated — and most dangerously incomplete — lines in Mexican tax folklore. The rule exists, but it has cases that double it to 10 years, clocks that stop while they audit you, and a cousin that everyone confuses it with: the extinction of the debt. Mastering these deadlines defines which papers you keep, which tax years are truly closed, and when a collection is already illegal.
Caducidad: the deadline to assess a liability against you (art. 67 CFF)
The SAT's powers to audit and assess omitted taxes lapse (caducan) in 5 years, generally counted from when you filed the return for the tax year (or from when you should have filed it). Two nuances move the clock: an amended return restarts the count with respect to what was modified — every correction hands the SAT new years on that item — and the deadline jumps to 10 years in the opacity scenarios: not being registered with the RFC (taxpayer registry), not keeping accounting records (or not preserving them for the legal period), and not filing the annual return while obligated to. The structural lesson: the orderly taxpayer lives in the 5-year world; the disorderly one, in the 10-year world — documentary order is, literally, half your exposure window.
The clock stops: the suspensions
Caducidad is suspended — it does not run — while the SAT exercises its audit powers (an on-site audit, a desk review, an electronic audit), when you file administrative appeals or lawsuits, when you cannot be located at your registered address, during a strike, upon death, and in other scenarios. The lock against eternity: the caducidad period plus its suspensions cannot exceed 10 years (with particular rules — moderate-to-high confidence on the combined cap; the fine computation of suspensions is one of the most litigated aspects of that article). In practical terms: if they audit tax year 2022 in 2027, that year's clock froze — do not count on it being "almost lapsed" while the review is alive.
Prescripción: the deadline to collect from you (art. 146)
A different concept, a different moment: once the tax debt already exists and is enforceable, the collection action lapses (prescripción) in 5 years — but every notified collection action (a demand, a seizure, any act of the administrative enforcement procedure, PAE) and every acknowledgment of the debt on your part (an installment payment request, for example) interrupts the period and restarts it from zero. Here too there is a ceiling: including interruptions, the period does not exceed 10 years (moderate-to-high confidence). The classic confusion: caducidad kills the possibility of assessing a new liability against you; prescripción kills the collection of one already assessed. They are raised at different moments, with different strategies — and both must be actively invoked — they do not operate on their own: the SAT will collect debts extinguished by prescripción until someone points it out through the correct defense remedy.
Do you have open tax years, old debts, or an archive you're not sure you can finally destroy?
The deadline map for your specific case — which tax years are legally dead, which clocks are suspended, which debts have already lapsed by prescripción and how to invoke it — is a one-session diagnostic with your timeline in front of you. And on the other side: the correct document-retention policy, so you never destroy the paper that a 10-year window can still demand of you.
Frequently asked questions
Does the lapse of powers (caducidad) apply on its own, or do I have to raise it?
You have to raise it: through a clarification request or as a ground of challenge in the defense remedies against the act that assesses liabilities for lapsed tax years, and you can even request a formal declaration of caducidad. In practice, the SAT rarely stops on its own — the deadline is your shield, but you have to lift it.
I received a collection demand for a debt from 8 years ago with no intervening action — has it lapsed by prescripción?
If the debt became enforceable more than 5 years ago and there were no legally notified collection actions or acknowledgments on your part that interrupted the clock, prescripción can be invoked — and the late demand itself does not revive it. Review the notification file (defects in notification are common) and raise it; it is one of the defenses with the best success rate when the facts back you up.
Does signing an installment payment agreement affect these deadlines?
Yes — it is an acknowledgment of the debt: it interrupts prescripción and restarts its count from zero. Sometimes doing so is exactly the right move; it just has to be decided knowing that this is the price. Never make a small payment to 'hold' an old debt without first checking whether it had already lapsed by prescripción.
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