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Mexico Tax Filing Guide 2026

Mexico's tax filing system is fully electronic through the SAT portal. The annual tax return (declaración anual) is due by 30 April, with monthly provisional payments required throughout the year for most taxpayers. Businesses must file DIOT reports on supplier transactions, issue CFDI electronic invoices, and maintain an active Buzón Tributario (SAT mailbox).

Annual Declaration (Declaración Anual)

The annual tax return is the definitive reconciliation of a taxpayer's annual income, deductions, and tax liability. The deadline is 30 April of the following year (e.g., the 2026 annual return is due by 30 April 2027). The annual return is filed electronically through the SAT portal (portal de SAT) using the Declaración Anual service. Both individuals (personas físicas) and legal entities (personas morales) must file. For individuals, the annual return aggregates all income types (salary, business, rental, capital gains, interest, etc.) and applies the progressive ISR rate schedule. Tax withheld by employers and provisional payments made during the year are credited against the final liability, resulting in either a balance payable or a refund.

Monthly Provisional Payments

Taxpayers with business or professional income must make monthly provisional payments (declaraciones provisionales) by the 17th of each month. These are estimated tax payments based on the previous month's income. The calculation differs by regime:

  • General regime: Monthly ISR is calculated on net profit (income minus deductible expenses) using the annual ISR rate schedule applied to the estimated annual income.
  • RESICO regime: Monthly ISR is a flat percentage (1–2.5%) applied to gross revenue, with no deductions.
  • Salaried employees: Generally do not file monthly returns; tax is withheld by the employer and remitted to the SAT monthly.

Monthly VAT (IVA) declarations are also due by the 17th. For taxpayers in the general regime, IVA is calculated as the difference between IVA charged (on sales) and IVA paid (on purchases).

DIOT (Declaración Informativa de Operaciones con Terceros)

The DIOT is an informative return that must be filed monthly by businesses that make payments to suppliers. It reports all transactions with third parties (suppliers, contractors, service providers) detailing the amount, RFC, and IVA breakdown. The DIOT is due by the same deadline as the monthly IVA return (17th of the following month). The SAT uses DIOT data to cross-check supplier income declarations and IVA collections. Penalties for late or incomplete DIOT filing can be significant.

CFDI Electronic Invoicing

All Mexican taxpayers must issue CFDI (Comprobante Fiscal Digital por Internet) electronic invoices for every transaction. CFDI is the backbone of Mexico's tax compliance system. Key requirements include:

  • Invoices must be generated through an SAT-authorized PAC (Proveedor Autorizado de Certificación).
  • Each CFDI includes a unique folio, digital stamp (sello digital), RFC of issuer and receiver, amount, IVA, and tax regime.
  • CFDI must be sent to the SAT in real time (within 72 hours of the transaction).
  • Payroll CFDI (CFDI de nómina) is required for all employee payments.
  • Receiving CFDI from suppliers is necessary to deduct expenses and claim IVA credits.
  • Receipts (complementos de pago) are required for installment payments.

Failure to issue CFDI results in fines and disallowance of deductions. The SAT uses CFDI data to prefill annual tax returns for most taxpayers.

Buzón Tributario (SAT Mailbox)

The Buzón Tributario is the official electronic mailbox managed by the SAT for all taxpayer communications. Every registered taxpayer must activate and maintain their Buzón Tributario. Through it, the SAT sends notifications (notificaciones), requirements for information, filing reminders, and audit notices. Taxpayers must respond to SAT notifications within the specified timeframe (typically 10–15 business days). Failure to respond can result in fines, tax assessments, and asset embargos. The Buzón Tributario is accessed through the SAT portal using an RFC password or e.firma (electronic signature).

E-Filing via the SAT Portal

All tax filings in Mexico are done electronically through the SAT's online portal (portal de SAT — sat.gob.mx). The portal provides access to:

  • Declaración Anual (annual return) filing
  • Monthly provisional ISR and IVA declarations
  • DIOT filing
  • CFDI consultation and generation
  • Buzón Tributario
  • RFC registration and modification
  • Tax opinions (opiniones de cumplimiento)
  • Payment of tax liabilities via SPEI or reference line

Taxpayers authenticate using their RFC password (contraseña) or e.firma (electronic signature). The SAT portal is available 24/7. Most returns are prefilled with data from CFDI, withholding declarations, and employer reports, simplifying the filing process.

FAQs

What happens if I miss the April 30 deadline?

Late filing incurs penalties (ranging from MXN 1,400 to MXN 22,790) plus monthly interest at the federal tax rate (recargos). The SAT may also issue a formal requirement.

Can I file my annual return online without an accountant?

Yes, the SAT portal prefills most data and guides taxpayers through the process. However, complex situations (foreign income, multiple income sources, investments) may benefit from professional assistance.

Do I need an e.firma to file taxes in Mexico?

An e.firma (FIEL — Firma Electrónica Avanzada) is required for legal entities and recommended for individuals. A password (contraseña) is sufficient for most individual filings.

Disclaimer

This guide provides general information about tax filing procedures in Mexico for 2026. Filing requirements, deadlines, and SAT portal features may change. The information is based on published SAT data and may not reflect individual circumstances. Always consult with a qualified Mexican tax advisor for advice specific to your situation. InvestmentKit does not provide tax advice.

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