SAT carta invitación (invitation letter): what it is, what to review, and how to respond on time

An alert in the Buzón Tributario (the SAT's electronic tax mailbox) and, once opened, a letter pointing out discrepancies between what you reported and what the SAT has in its databases. It tends to provoke two costly reactions: paying without reviewing, as if it were an audit, or leaving it unopened. Knowing what it is, which deadlines run, and what the Supreme Court has said makes a measured response possible.

What the letter is not: an audit act. Audit powers are set out in Article 42 (requesting accounting records, conducting on-site audits, reviewing statutory tax audit reports) and begin with the first act served on the taxpayer. The desk audit under Article 48 opens with a request for documents and leads to a letter of findings (oficio de observaciones), with twenty days to rebut it. The letter opens none of those channels.

Not being an audit does not mean it has no effect: according to the Second Chamber, the letter reports an amount recorded in the authority's files, which the authority will take into account if it later exercises its audit powers over that period. If it is served through the Buzón Tributario, moreover, Article 17-K requires you to check the mailbox within three days of the electronic alert and, under Article 134, if the document is not opened within that period, service is deemed made on the fourth day.

It is merely a declaratory act, through which the authority urges the taxpayer to correct its tax situation regarding the omissions detected, presenting a payment proposal that causes no actual harm to the taxpayer's legal sphere.

Letters may arrive through the Buzón Tributario, which Article 17-K assigns to every person with an RFC (Mexican taxpayer ID number), but also by email or at your address, channels the SAT mentions for letters on the collection of tax debts. Whatever the channel, do not use the links or phone numbers in the message: log in to the SAT portal with your password or e.firma (SAT advanced electronic signature) and check the letter there.

• If it concerns tax debts, it must bear an invitation number (the SAT states that all Cobro Persuasivo, or voluntary collection, letters carry one), which you can validate on its Adeudos fiscales (tax debts) page, Consulta tab.
• If it is electronically signed, the SAT allows you to verify its integrity and authorship with the folio number, your RFC, and the last eight characters of the signature, or with the document's QR code (Articles 17-I and 38 of the CFF).
• The SAT does not request information or passwords by email or phone, identifies itself clearly, and every payment is made with a línea de captura (payment reference). If in doubt, call MarcaSAT, the SAT's helpline: 55 627 22 728.

With the genuine letter in hand, reconstruct the discrepancy it identifies and decide on the basis of documents, not in haste.

1. Open and save the document

   If it arrived through the Buzón, open it within three business days of the alert. Save the receipt and the letter; note the date, control number, and deadline.

   Deadline: 3 business days after the alert

2. Find the source of the discrepancy

   Check the period against your CFDI (electronic tax invoices), accounting records, and payments. Obtain your tax compliance opinion (Article 32-D of the CFF) to rule out unfiled returns or final assessments.

3. Clarify, if the discrepancy does not exist

   Follow the channel and deadline stated in the letter. For a deep oversight invitation letter, the SAT allows ten business days from service or from the interview and accepts the clarification at the institutional email address given in the letter, at the interview, or in Mi portal. Notices of unfiled returns can be clarified in Mi portal at any time. Keep the receipt with its folio number.

   Deadline: Per the letter, or 10 business days

4. Self-correct, if the discrepancy is real

   File the amended return with inflation adjustment and late-payment surcharges. Article 32 of the CFF allows a return to be amended up to three times as long as no audit has been initiated, and more times when the amendment only increases income or reduces deductions.

5. Document the decision not to act

   Not acting is also an option, but a reasoned one, in writing: what was reviewed, why the discrepancy does not apply, and what evidence supports that conclusion.

In binding precedent (jurisprudencia) 2a./J. 62/2013 (10a.), the Second Chamber of the Supreme Court held that the carta invitación to regularize income tax (ISR) on cash deposits is not a final ruling that can be challenged in administrative litigation before the TFJA (Federal Court of Administrative Justice), but a declaratory act causing no actual harm to the taxpayer. In 2a./J. 110/2019 (10a.), it extended that criterion to the decision rejecting a clarification filed against the letter, as long as that decision does not determine an amount payable or establish legal consequences, warnings of sanctions, or loss of benefits.

The consequence is twofold: as long as the document is merely an invitation, with no fine, determined amount, or warning, there is no remedy to exhaust and no deadline lost by not pursuing one; but neither is there any lawsuit to stop the authority if it later reviews the same period. If what you received is a formal request with a fine or a ruling that sets a tax assessment (crédito fiscal), seek advice immediately: in that case, deadlines do run. Article 33-A of the CFF confirms that clarifications do not constitute a formal proceeding and do not interrupt deadlines. The defense is built against the subsequent act that actually defines the obligation, with the file assembled upon receiving the letter.