Mexico Tax Deadlines — October 2026: Calendar, Amnesty Program, and What's Ahead for RESICO

By SWB · Accounting, tax, and business advisory · October 2026

October packs key filing deadlines, the final stretch of Mexico's tax amnesty program, and Congress's debate over the 2027 Economic Package. Here is what matters, straight to the point.

Your September return is due October 19

September monthly filings — provisional ISR payments, definitive IVA payments, IEPS, withholdings, and the DIOT — are generally due on the 17th of each month. Since October 17, 2026 falls on a Saturday, the deadline rolls to the next business day: Monday, October 19.

Under the sixth-digit-of-your-RFC rule, individuals and companies in the general regime get extra business days:

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The extensiondoes not apply to large taxpayers or those required to have audited financial statements. Under RESICO, confirm your date in the SAT portal. September employer IMSS contributions are also due October 19.

Don't miss these dates: in 2026, late-payment surcharges run 2.07% per month, and fines for unfiled returns range from MX$2,050 to MX$25,360 per omitted obligation.

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Tax amnesty: a door closes on October 31

The regularization program offers up to 100% relief on fines, surcharges, and enforcement costs on tax debts from 2024 and earlier years. The underlying tax itself must still be paid in full, updated for inflation.

• Final tax assessments (créditos fiscales firmes): apply no later than October 31, 2026, paying in one installment or up to 6 installments.

Voluntary self-correction: single payment no later than December 31, 2026.

It covers individuals and companies with up to MX$300 million in 2024 income. Through August, SAT reported over MX$6.4 billion recovered from more than 38,000 participating taxpayers. After October 31, the window for final assessments closes.

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2027 Economic Package: what's proposed for RESICO

The 2027 Economic Package, presented September 8 and now before Congress, creates no new taxes and raises neither ISR nor IVA rates. For RESICO it proposes:

• Income cap raised to MX$5 million (individuals) and MX$50 million (companies).

• Optional 7% IVA on amounts actually collected, with no crediting (individuals).

• A single ISR + IVA return, replacing two monthly filings.

• Missed payments regularizable in installments, with no automatic expulsion from the regime.

Worth clarifying: under current 2026 law, individuals under RESICO no longer file an annual ISR return — monthly payments are definitive. Congress will decide the package between October and November; if approved, it takes effect January 1, 2027.

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The backdrop: peso, rates, and markets

The peso closed September near MX$17.94 per dollar (up about 5% on the month), Banxico held its rate at 6.50% while the U.S. Federal Reserve raised to 3.75%–4%, and the U.S. 10-year Treasury yield topped 5.2%, its highest in 19 years. The takeaway for SMEs: credit stays expensive for a while — protect liquidity and stay selective with financing.

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Need help with your filing or the amnesty program?

SWB has spent 20+ years helping entrepreneurs, freelancers, startups, and SMEs stay compliant — without overpaying. Focus on your business; we'll handle the rest.

Message us on WhatsApp or use the contact form at swb.com.mx.

This article is for informational purposes and does not replace personalized tax advice. Legislation cited reflects current law and proposals under discussion as of September 29, 2026.