What Is a Tax Regime in Mexico?
A tax regime (régimen fiscal) is the category under which an individual or a company pays taxes to Mexico's SAT, and it determines which taxes apply, what deductions are allowed, and what type of CFDI that taxpayer can issue or receive. Every tax regime has a three-digit code — like 601 or 626 — that appears on the taxpayer's Constancia de Situación Fiscal (CSF, or tax status certificate) and must be entered exactly the same way on every invoice for a CFDI 4.0 to be valid.
Knowing your correct tax regime isn't optional paperwork: if you issue or receive invoices with the wrong code, the authorized certification provider (PAC) can reject the stamping, or SAT can later challenge the deduction.
Why the Tax Regime Must Match the CSF
Since CFDI 4.0 took effect, SAT requires the recipient's data — including their tax regime — to match exactly what's on their current Constancia de Situación Fiscal. If the tax regime you enter on the invoice doesn't match what your client has on file, the PAC rejects the stamping before the CFDI ever gets created, and the whole process stops right there.
That changed the invoicing workflow for a lot of businesses: asking a client for their RFC is no longer enough. You also need their current tax regime and their fiscal zip code, and you need to confirm both against their CSF before issuing the invoice. On top of that, the recipient's tax regime limits which "CFDI use" is valid for that invoice: a payroll tax regime, for example, doesn't accept the same uses as a business-activity tax regime.
SAT Tax Regime Catalog: The Most Common Codes
The official c_RegimenFiscal catalog from Annex 20 lists around twenty active codes, but the vast majority of invoices issued by a business in Mexico only use a handful of them:
- 601 — General de Ley Personas Morales (general regime for corporations)
- 603 — Personas Morales con Fines no Lucrativos (non-profit legal entities)
- 605 — Sueldos y Salarios e Ingresos Asimilados a Salarios (wages and salary-like income)
- 606 — Arrendamiento (real estate leasing)
- 612 — Personas Físicas con Actividades Empresariales y Profesionales (individuals with business or professional activity)
- 616 — Sin obligaciones fiscales (no standing tax obligations)
- 621 — Incorporación Fiscal (a legacy small-business regime)
- 625 — Régimen de las Actividades Empresariales con ingresos a través de Plataformas Tecnológicas (income through tech platforms)
- 626 — Régimen Simplificado de Confianza, known as RESICO
Each code corresponds to a different type of taxpayer, and filing under the wrong one can cause both invoice-stamping errors and problems when it's time to file.
Tax Regime for Individuals: Which One Applies to You
Most individuals in Mexico fall under one of these regimes, depending on where their income comes from:
- 605 (Wages and Salaries): for anyone working under a formal employment relationship, where an employer withholds taxes on their behalf.
- 606 (Leasing): for anyone renting out real estate — commercial space, apartments, warehouses — when that rental income is what they report.
- 612 (Business and Professional Activities): the most common regime for freelancers, independent professionals, and business owners operating as an individual rather than through a formal corporation.
- 616 (No Tax Obligations): used in specific cases, such as when an individual receives donations or exempt income and has no regular economic activity to report.
- 621 (Incorporación Fiscal): a regime being phased out, reserved for taxpayers who were already enrolled before RESICO replaced it as the entry-level option for small businesses.
- 625 (Technology Platforms): for anyone earning income through ride-hailing, delivery, lodging, or marketplace apps, where the platform withholds a portion of income tax and VAT.
- 626 (RESICO): the Simplified Trust Regime for individuals whose annual income falls under the legal cap, designed to simplify tax payments with reduced rates. We cover it in full in our guide to what RESICO is.
Tax Regime for Companies: Which One Applies to You
For legally incorporated companies, the catalog narrows down to two codes used most often:
- 601 (General Regime for Corporations): the default tax regime for most for-profit corporate entities — S.A. de C.V., S. de R.L., and similar structures — carrying out business activities.
- 603 (Non-Profit Legal Entities): for civil associations, foundations, and similar organizations that don't pursue profit, though some still have specific filing obligations.
If your business changed its line of work or grew past the point where it still qualifies as an individual with business activity, the common next step is incorporating as a company under regime 601.
How to Check Your Current Tax Regime
The most reliable way to confirm your current tax regime is to download your Constancia de Situación Fiscal directly from SAT's portal using your RFC and password, or your e.firma. That document shows the exact code and name of the regime you're registered under as of that moment, along with the date it took effect.
Don't rely on what you remember from a year ago: it's possible to switch tax regimes — for example, moving from business activity into RESICO — and if you keep invoicing under the old code, your CFDIs stop matching your actual standing with SAT. We walk through the full process of obtaining and reading this document in our guide to the Constancia de Situación Fiscal.
What Happens If You Invoice Under the Wrong Tax Regime
Entering the wrong tax regime on a CFDI isn't a minor detail. It can cause the PAC to reject the stamping outright if the code doesn't match the recipient's CSF, keep the client from deducting the expense because the CFDI use tied to that regime isn't compatible, or force you to cancel and reissue the invoice — with all the administrative back-and-forth that involves once time has passed since the original transaction.
That's why it pays to validate the tax regime before invoicing, not after, alongside the rest of the requirements to invoice that SAT expects. Businesses that invoice a high volume of clients often automate this validation as part of their CFDI invoicing process, rather than trusting that every client will text them the right code.
Frequently Asked Questions
What's the difference between tax regime 605 and 612?
Regime 605 is for anyone receiving a salary under a formal employment relationship, with taxes withheld as an employee; regime 612 is for individuals invoicing for their own business or professional activity, without depending on an employer.
Can I be registered under more than one tax regime at the same time?
Yes. An individual can be registered under more than one regime at once — for example, wages and salaries (605) alongside leasing (606) — and must use the correct code depending on the type of income being invoiced in each case.
Which tax regime does RESICO use?
RESICO corresponds to code 626 for individuals. It's designed to simplify tax payments for small businesses with reduced income-tax rates, as long as annual income stays under the legal cap.
Where do I check a client's exact tax regime?
On their current Constancia de Situación Fiscal. Asking for that document before invoicing keeps you from entering an outdated tax regime that gets the CFDI rejected at the stamping stage.
Does my tax regime change if my economic activity changes?
It can. If your main economic activity changes significantly — say, you stop leasing a property and start invoicing for professional services instead — it's common to also need to update your tax regime with SAT.
If your business invoices different types of clients and you want to stop a mismatched tax regime from blocking your stamping, at AISDC we build CFDI invoicing solutions that validate recipient data against their Constancia de Situación Fiscal before each invoice goes out.