June brings a date many individuals leave until the end: the monthly return for May. If you have business activity, professional services, leasing income or VAT to review, the work is not only entering the portal and sending numbers. The important work happens before filing: matching CFDI, bank records, collections, expenses, withholdings and workpapers.
SAT's filing service for individuals with business activity, professional services, leasing and VAT uses monthly filing logic. For May 2026, that makes it relevant to review the information before June 17, not late at night on the same day.
Quick Traffic Light Before Filing
| Situation | Practical reading | Recommended action |
| Everything reconciles | CFDI, bank records and taxes explain the same period | File and save acknowledgment, payment line and workpaper |
| Minor difference | The difference has a clear and supportable explanation | Document the cause before sending |
| Material difference | ISR, VAT, withholdings or deductions may change | Pause filing and review with tax criteria |
| Missing support | The number may be right, but cannot be proven | Locate XML, bank statement or receipt before close |
What to Review Before Entering the Portal
- Issued CFDI for May: active invoices, canceled invoices, substitutions and credit notes.
- Received CFDI: deductible expenses, payment method, CFDI use and operation support.
- Bank records: deposits, fees, supplier payments, transfers and unidentified movements.
- VAT: collected, paid, creditable and differences from partial payments or pending invoices.
- ISR: taxable income, deductions, withholdings and prior provisional payments.
- Acknowledgments: previous returns, payment lines, payments and amended filings if any.
Why Pre-Filled Data Is Not Enough
Pre-filled data helps, but it does not replace control. The portal may show CFDI and relevant data, but you still need to know whether an invoice was collected, whether an expense corresponds to the activity, whether a withholding was applied correctly or whether a deposit is not income.
When that review is skipped, the system becomes a calculator with incomplete data.
If You Detect Differences This Week
- Do not file only to remove the pending task.
- Identify whether the difference comes from CFDI, bank records, VAT, withholding or accounting classification.
- Save evidence: XML, PDF, bank statement, contract, payment receipt or movement explanation.
- Decide whether the difference can be corrected before filing or needs tax criteria.
- Leave a closing note so next month does not start with the same issue.
Minimum File You Should Be Able to Open Later
- Final workpaper with ISR and VAT figures.
- Folder with issued, received, canceled and substituted CFDI.
- Bank statement for the period with movements marked or reconciled.
- Return acknowledgment, payment line and proof of payment if applicable.
- Short note with differences, decisions and pending items for the next month.
That file is not bureaucracy. It is what lets you explain a return months later, when no one remembers why a deposit was not income or why an invoice was substituted.
How Fintax Can Help
Fintax can help prepare the monthly close with CFDI, bank, VAT, ISR and evidence review. The goal is to file on time, but also to file with enough support if a difference needs to be explained later.