No monthly close can stop SAT from exercising its audit powers. It can stop an ordinary difference from arriving unexplained in an invitation letter, a compliance clarification or a formal review.
Start with the period you need to review. Gather the return, its calculations, and the records supporting each amount. Some adjustments have no separate invoice or bank transaction; identify the supporting record that applies to each item.
What to review for the problem you found
- For an invitation letter, identify the period, the data compared and the available evidence before replying or amending a return.
- When bank records do not match CFDI, separate invoices not yet collected, collections awaiting an invoice, transfers, loans, advances and unidentified deposits.
- For a negative compliance opinion, address the exact inconsistency shown and preserve the correction or clarification receipt.
- For a Tax Mailbox alert, enter through sat.gob.mx, download the document and receipt, and distinguish a formal notice from a message of interest.
Controls that leave usable evidence
Validate the XML and its SAT status instead of retaining only a PDF. Keep the cancellation request, the recipient's response and the relationship between the original and replacement CFDI. The SAT cancellation process identifies the applicable reason codes and replacement link.
Review bank activity throughout the year to identify collections, transfers, loans, and advances. For an unexplained deposit, record who will investigate and which document is missing. Waiting until year-end can make that information harder to obtain.
A positive compliance opinion reports a system status. It does not approve the accuracy of the underlying calculations. Review the exact condition when the result is negative.
Do not treat every SAT message alike
An email or text message only tells you that content is waiting in the Tax Mailbox. The document and notification receipt are inside the official portal. SAT Tax Mailbox guidance warns that incorrect or unauthentic contact methods can lead to notice by public posting and temporary restriction of the digital seal certificate.
An invitation letter is also different from an electronic audit. SAT's electronic audit service states that an electronic audit begins with notice of a provisional resolution and pre-assessment. Preserve the complete notice and obtain tax review before correcting or replying.
Close the month around the real filing date
- Validate issued and received CFDI, their status and their link to the recorded transaction.
- Reconcile bank activity, accounting and returns, then assign every pending item to a named owner.
- Archive the return, filing receipt, payment reference, proof of payment and final workpaper together.
- Log each Tax Mailbox review with date, owner, result and a copy of every current document.
How Fintax can help
Fintax can compare CFDI, bank records, and returns, then organize a response that links each SAT question to its supporting documents. Keep a copy of the complete response and attachments, along with the submission acknowledgment.
Start with differences that cross systems
Prioritize mismatches between CFDI, banks, returns and accounting because they are easier to detect and harder to explain later. Keep an exception log with amount, period, cause and correction status. This creates a review trail before an authority request arrives.
