Quick Answer
For August 2026, July monthly filings have a base date of Monday the 17th and may extend from the 18th to the 24th based on the sixth numeric digit of the RFC; July IMSS/SIPARE contributions are due on the 17th; and the July DIOT, if applicable, must be filed during August, with Monday the 31st as the operational limit. The Tax Mailbox has no monthly date: open each notice within three business days.
Organize August 2026 with responsible parties, internal cutoffs, and evidence for SAT, IMSS, DIOT, CFDI, and Tax Mailbox.
Verify Before Filing
Dates and obligations depend on the taxpayer. Check the official calendar and current tax status before using this dashboard.
August Operational Dashboard
How to read the dates: August 17 is the base filing date; the sixth-digit RFC facility may move it from the 18th to the 24th. The DIOT covers July and applies only to taxpayers required to file it. For the Tax Mailbox, the three business days run from the notice; there is no fixed monthly deadline.
August Checklist
- Confirm active obligations in the certificate and tax file.
- Assign a responsible person and backup for each obligation.
- Set internal cutoff before the official deadline.
- Gather CFDI, bank statements, payroll, suppliers, and affiliation movements.
- Save filing, acknowledgment, payment slip, and proof of payment.
From the official calendar to the team dashboard
- Extract obligations from the taxpayer’s file.
- Cross-check dates with SAT, IMSS, and official sources.
- Define information and review cutoffs per obligation.
- File and pay with operational margin.
- Close each task only when the file is complete.
Four calendar mistakes
- Copying a generic calendar without validating active obligations.
- Confusing the official date with the internal preparation date.
- Marking as completed without saving acknowledgment and payment.
- Leaving the Tax Mailbox without a responsible person during vacations.
What you must confirm before using any calendar
In August, monthly filings, social security payments, payment complements, DIOT reviews, and Tax Mailbox communications often coexist. Not all apply to every taxpayer, and the date may depend on regime, obligation, or the sixth digit of the RFC.
The correct list is obtained from each taxpayer’s file and cross-checked with the official calendar. This tool works as a preparation dashboard, not as a substitute for individual obligation consultation.
How to turn dates into an operational calendar
If a filing is due on the 17th, the team should not start on the 16th. Define internal cutoffs: complete information, reconciliation, review, authorization, and submission. The official date is the external limit; your internal date should allow time to correct differences and obtain acknowledgments.
A useful calendar not only shows deadlines: it shows who prepares, who reviews, what evidence is missing, and when it must be internally closed.
— Fintax
Frequently Asked Questions
Does everything expire on the 17th?
No. August 17 is the base date for July monthly filings and the deadline for July IMSS/SIPARE contributions. The sixth-digit RFC facility may extend certain filings through the 24th; the July DIOT is filed during August, and the Tax Mailbox depends on each notice.
What date should I put in my internal calendar?
A date before the deadline that allows for reconciliation, review, authorization, filing, and correction without working at the last minute.
What evidence proves compliance?
Keep the filing, acknowledgment, payment slip, proof of payment, and working papers explaining the calculation.
Sources and further reading
Consult official sources: monthly deadlines for legal entities, monthly deadlines for individual taxpayers under RESICO, DIOT deadline and filing, IMSS SIPARE legal basis and deadline, Tax Mailbox notices, RMF 2026.
To complete the process within Fintax, review: monthly filings and acknowledgments guide, Tax Mailbox routine, SIPARE review.
What to do now
Turn this review into a file with responsible person, date, source, and evidence. If there is a material difference, a past-due obligation, or a decision that changes the calculation, validate the case with your accounting responsible before filing, canceling, or paying.
