Monthly SAT Returns in RESICO: What to Review

A monthly RESICO return looks simple because the SAT portal shows pre-filled information. The mistake is treating that pre-fill as final. The taxpayer still needs to review CFDI, collections, withholdings, VAT and acknowledgments before filing.

SAT states that the monthly RESICO return is used to declare ISR and VAT and is fed by issued and received tax receipts. You can confirm this in the official monthly and definitive RESICO return service. The tool helps, but it does not know everything that happened in your bank account or fix poorly stamped invoices by itself.

The point most taxpayers miss

Monthly SAT returns in RESICO: collection review

Under RESICO, ISR is calculated on income actually collected. The important number is not only what was invoiced, but what was collected during the period. If a CFDI is issued in March and paid in April, that difference needs to be documented so that unpaid income is not treated as collected.

SAT's RESICO invoice viewer helps review invoice amounts used for pre-filling returns. It is a starting point, not the end of the analysis.

Practical example

Assume you issued an invoice for MXN 50,000 in March, but the client paid MXN 30,000 in March and MXN 20,000 in April. If the system takes the full invoice and you do not review the actual collection, you may pay ISR on income you have not yet received.

Monthly movement	Period to review	Evidence to keep	Common mistake
Invoice issued and fully collected in the same month	The collection month	CFDI, bank deposit and customer reference	Accepting the pre-fill without matching the deposit
Invoice issued but still unpaid	Keep it in the receivables review until collection	CFDI plus accounts-receivable detail	Treating the full invoice as collected income
Partial payment	Allocate each collection to its actual month	Bank movements, invoice balance and payment complement when applicable	Reporting the full amount in the first month or losing the remaining balance
Client applied a withholding	The month reflected by the payment and supporting CFDI	Withholding data, CFDI, bank receipt and working paper	Missing a withholding because it was stamped incorrectly or appeared late

A better monthly close works like this:

Identify CFDI issued during the month.
Separate collected invoices from pending ones.
Review payment complements where applicable.
Keep bank statements and proof of collection.
Adjust the information before filing only when the portal allows it and you have support.

What to review before filing

Monthly SAT returns in RESICO: pre-filled data

Before clicking submit, do a short but disciplined review. You do not need to turn every close into an audit, but you should avoid letting the system rely on incomplete data.

1. Issued CFDI against bank collections

Compare income invoices with actual deposits. If there are partial payments, advances or clients that pay later, keep the supporting evidence in the month's folder. This prevents both overpayment and omitted collected income.

2. ISR and VAT withholdings

When working with legal entities, withholdings may apply. Confirm that the CFDI and payment show the withholding correctly. If the client withheld tax but the receipt is wrong, the portal may fail to recognize it and the payable balance will be distorted.

3. VAT charged, creditable and withheld

RESICO simplifies ISR, not VAT. Review whether transactions trigger VAT, whether creditable VAT is valid and whether any withholding applies. The difference between invoiced, collected and withheld matters.

4. Prior returns and amended filings

If you find an error from a previous month, do not hide it with an informal adjustment. Review whether an amended return is needed and keep working papers. A small difference repeated over months can end in a SAT notice.

Common mistakes

The most common problems are routine slips:

Accepting pre-filled data without comparing it to bank records.
Declaring invoices that have not been collected.
Failing to invoice income that was already collected.
Forgetting payment complements.
Assuming client withholdings were stamped correctly.
Not saving acknowledgments, payment lines and proof of payment.

A 30-to-60-minute monthly routine can prevent hours of corrections later. If the volume no longer fits manual review, it is worth using an accountant or platform that downloads CFDI, reconciles bank records and keeps evidence.

When to ask for help

If income comes from several clients, payments are partial, withholdings apply or differences appear every month between SAT data and your records, improvising is not worth it. A preventive review is usually cheaper than correcting expired returns.

At Fintax, CFDI, collections and returns are reviewed before the deadline, not after SAT has already shown an inconsistency. That changes the tone of compliance: less urgency, more control.

Frequently asked questions

When is the monthly RESICO return filed?

Generally by the 17th day of the month immediately following the period being filed. Additional days may apply depending on the sixth digit of the RFC and the applicable rules.

Can I accept SAT's pre-filled data?

You can use it as a base, but you must review it. Pre-filled data depends on CFDI and may not reflect actual collections, incorrectly stamped withholdings or pending adjustments.

What if SAT shows income I have not collected yet?

Review CFDI, payment complements and bank statements. If the portal allows an adjustment, make it only with enough supporting documentation. If it is unclear, request accounting review before filing.

Do I need to file if I had no income?

It depends on your registered obligations. Review your tax status certificate and the applicable period before assuming that no filing is required.

Monthly SAT Returns in RESICO: What to Review Before Filing