An invoice is missing, a return does not match your records or a notice has appeared in Buzon Tributario, Mexico's Tax Mailbox. Start by identifying the document and period involved. You can often collect the records yourself, then decide whether you need help understanding or correcting the problem.
Escalate when the decision changes the record
Routine downloads and reconciliations can often be handled internally. Ask for specialized review when the next step changes a filed return, cancels a CFDI, answers an authority notice or changes the tax treatment of a material transaction. Those actions are harder to reverse and deserve documented criteria before execution.
You can safely retrieve documents, verify a CFDI and list discrepancies without making a tax decision. Filing an amended return, canceling an invoice or answering a formal notice is different. Those actions can affect tax, deadlines and the evidence available for a later review.
The examples below can help you decide what to do next. The answer will depend on your tax regime, the transaction and, if you received a notice, what it asks you to do.
Start by classifying the task
Different tasks need different kinds of review:
| Level | Typical task | Sensible next step |
|---|---|---|
| Verification | Download a tax status certificate, retrieve a receipt, verify a CFDI or list Buzon messages | Do the read-only check and preserve the evidence |
| Accounting judgment | Amend a return, replace a CFDI, request a refund, change regime or classify a mixed transaction | Ask an accountant or tax advisor to quantify the effect first |
| Formal procedure or defense | Answer a requirement, challenge a tax credit, handle an audit or denied refund, or check a deadline | Obtain prompt tax legal review and preserve the full notification file |
The amount at stake is not the only test. A small error repeated across many months can deserve more attention than a larger, isolated discrepancy. An approaching deadline or an irreversible action also moves the matter up a level.
Use official SAT sources in the right order
Check what each official document tells you before using it to make a decision:
| Official source | What it can establish | What it does not establish by itself |
|---|---|---|
| CFDI verification service | Whether the invoice was certified and its reported status | Deductibility, business purpose, materiality or correct tax treatment |
| Tax situation certificate | The taxpayer data and obligations registered with SAT | That every registered obligation is correct for the actual activity |
| Tax compliance opinion | SAT's system status under the applicable compliance rules | A favorable ruling on the accuracy of returns or calculations |
| Filed return receipt | What was transmitted, when and under which filing reference | That the return reconciles to accounting, CFDI and bank records |
| Buzon Tributario | Messages, administrative acts and the related electronic record | The correct response, legal strategy or calculation of every deadline |
Compare SAT's records with your invoices, bank statements and calculations. An invoice can be valid in the verification service but contain an incorrect amount. A submitted return may still need correction if it omitted income or counted a deduction twice.
Treat a Buzon alert according to its content
Buzon Tributario carries both informational messages and formal administrative acts. The visual presence of an alert does not tell you which one you received.
Enter through sat.gob.mx rather than an email link. Download the complete document, its attachments and the notification receipt. Record the date when the alert arrived, the date when the mailbox was opened and the person who accessed it. Keep the original files instead of relying on screenshots alone.
SAT explains how electronic notification works, including the period to open a pending notice. The exact deadline for answering or challenging the act depends on the document and the applicable procedure. Do not calculate it from memory or assume that filing a general clarification pauses it.
Escalate promptly when the document mentions a requirement, provisional resolution, tax credit, audit, seizure, cancellation, restriction, refund denial or a period to respond. The advisor should receive the full PDF and notification evidence, not a paraphrase of the email alert.
What you can usually do yourself
Read-only work is valuable because it makes later advice faster and more precise. You can usually:
- retrieve CFDI, XML files, returns, filing receipts and certificates;
- verify whether a CFDI appears in the SAT service and record its status;
- list differences between CFDI, bank deposits, accounting and filed returns;
- build a timeline of notices, filings, payments and prior corrections;
- identify the periods and obligations involved; and
- write down the decision you need, without changing records yet.
Keep a simple evidence index with file name, source, period and download date. If a portal result can change, save the PDF or receipt generated at the time of the check.
When to ask for a review before making changes
Ask for review before an action that is hard to reverse, affects several periods or relies on a disputed classification. Common examples include:
- filing an amended return to make a portal discrepancy disappear;
- canceling and replacing a CFDI without checking its effect on both parties;
- paying an amount before confirming the concept, period and reference;
- changing a tax regime based only on projected savings;
- answering a formal notice without addressing every fact and attachment; or
- requesting a refund without reconciling the balance and its supporting evidence.
Before changing a figure, identify where the difference began. If the source is an incorrect invoice, changing only the return may leave the same problem in your accounting records or another period.
Prepare a consultation packet
Send the advisor the relevant records with a short explanation of what you need to resolve. A file list helps them find the documents and tell you what is missing.
Include:
- The exact question and the decision you need.
- RFC, tax regime, activity, obligation and period involved.
- The complete SAT document, attachments and notification receipt, if any.
- CFDI in XML and PDF format, filed returns and payment receipts.
- Bank records, contracts and operational evidence tied to the transaction.
- A timeline of what happened and what has already been filed, paid or answered.
- Your own reconciliation, with facts separated from assumptions.
Do not send the private key for your e.firma, its password or a digital seal certificate password by ordinary email. SAT describes the e.firma as a signature under the holder's exclusive control and equivalent to a handwritten signature. An advisor can prepare files and instructions while the authorized taxpayer controls the final signature.
Choose the professional by the problem
An accountant is often the right first contact for reconciliations, returns, CFDI effects and recurring compliance. A tax lawyer is appropriate when the matter involves a formal act, procedural deadline, tax credit, audit strategy or legal defense. Some cases need both, with one person owning the calculation and another the procedure.
PRODECON also provides free federal tax guidance and can route eligible matters to services such as legal representation, complaints or conclusive agreements. Its scope and representation requirements should be checked for the specific case.
Ask who will perform the work, which documents they need and how they calculate the fee. Confirm whether you will receive advice only or whether the service includes preparing and submitting a correction or response.
What a useful advisory answer should contain
| Deliverable | Practical test |
|---|---|
| Defined issue | It identifies the tax, period, transaction and question being resolved |
| Verified facts | It distinguishes documents reviewed from facts still assumed |
| Applicable basis | It cites the rule, procedure or official criterion that supports the analysis |
| Options and calculations | It shows the effect, risk and reversibility of each realistic path |
| Deadline and owner | It states what must happen, by when and who controls the action |
| Evidence checklist | It lists what to file, retain or obtain before closing the matter |
The advisor may need more information before reaching a conclusion. Ask them to identify the missing document, explain who can provide it and agree on when the review will resume.
If the right step is a SAT clarification
SAT's electronic clarification service allows taxpayers to describe an issue and attach supporting documents. Preserve the submission receipt, the exact attachments and every later response.
A clarification is useful when the official procedure fits the issue and the evidence can explain the discrepancy. It is not a universal substitute for a return, a formal response or a legal remedy. Unless the applicable rule says otherwise, do not assume that submitting one extends another deadline.
A quick decision test
Before proceeding alone, ask four questions:
- Am I only retrieving or comparing information?
- Will this action change a CFDI, return, payment, registration or formal response?
- Is there a deadline, several affected periods or a document I do not understand?
- Could the action weaken evidence or be difficult to reverse?
You can usually retrieve and compare records yourself. If you are considering a change and cannot explain its effect, ask for a review first. Mention any deadline at the outset so the advisor can assess the urgency.
How Fintax can help
Fintax can compare the relevant invoices, returns and bank records, review a SAT notice and explain what needs to happen next. Bring the full document and any earlier response so we can check what has already been handled.
Can I trust a valid CFDI as proof that the expense is deductible?
No. SAT verification can confirm certification and status, but deductibility also depends on the transaction, requirements, business purpose and supporting evidence.
Does a positive tax compliance opinion prove that my returns are correct?
No. SAT states that the opinion is not a favorable resolution on the correct calculation of taxes. It reports compliance status under the applicable rules.
Should I answer every Buzon message through a clarification?
No. First determine whether it is informational or a formal administrative act and identify the procedure named in the document. A general clarification may be the wrong channel and may not protect a separate deadline.
What is the safest first step after receiving a SAT notice?
Download the full notice, attachments and notification receipt from SAT, record the dates and obtain a review before editing returns or submitting a response.
Official links to complete the task
Open official services from a new browser tab, confirm the taxpayer and period, and save the resulting acknowledgment or evidence with the case.
