RFC and Constancia de Situación Fiscal When Buying a Home

When it's time to sign the deed (escritura) for a home, the same last-minute surprise almost always shows up: the notary public (notario público) asks for the RFC and the Constancia de Situación Fiscal (Tax Status Certificate) from both the buyer and the seller. Many people don't know what these documents are for or how to get them, and a single incorrectly entered detail can delay the closing by several days. In this guide we explain, in plain language and with information current for 2025-2026, why they are essential, how to get your constancia, and what to do if you are a foreigner.

RFC and Constancia de Situación Fiscal: what they are

The RFC (Registro Federal de Contribuyentes, or Federal Taxpayer Registry) is the code the Servicio de Administración Tributaria (SAT), Mexico's tax authority, uses to identify every individual or legal entity that carries out activities with tax effects in Mexico. It is made up of letters and numbers derived from your name and date of birth, plus a homoclave that makes it unique.

The Constancia de Situación Fiscal is an official document issued by the SAT that summarizes your current tax information: your full RFC, your name or business name, your registered tax address, your tax regime, and your status with the authority. In a real-estate transaction it works as a kind of "tax ID" that backs up the details that will be recorded in the deed.

Why the notary asks for them

The sale of a property creates tax obligations for both parties, and the notary acts as an auxiliary of the tax authority: he or she is required to calculate, withhold, and remit certain taxes arising from the transaction. To do this correctly, the notary needs to identify both buyer and seller unambiguously before the SAT.

What the notary backs up with your RFC

• Calculation and withholding of the ISR (income tax) owed by the seller on the gain from the sale. You can see how it works in our guide on ISR on the sale of a home.
• Issuance of tax certificates and receipts related to the transaction.
• Reporting to the SAT the transfer of the property with the correct details of the parties.
• Accurate recording of the tax address and tax regime that will appear in the public deed.

If the tax details don't match the SAT's records, the notary may refuse to close the transaction until they are corrected, since the notary is responsible for the information reported. That's why it's best to bring the constancia at the start of the process rather than leaving it for signing day.

How to get your Constancia de Situación Fiscal

Getting the constancia is free, and in most cases you can do it yourself in a few minutes. Here are the most common ways; keep in mind that the SAT updates its portals frequently, so confirm the current steps on its official site:

Options for getting it

1. Log in to the SAT portal and look for the "Constancia de Situación Fiscal" option, identifying yourself with your RFC and password (Clave CIEC) or with your e.firma (electronic signature).
2. Use the official mobile app "SAT ID" or "SAT Móvil," which lets you generate the constancia with your RFC and login details.
3. Go to a SAT office with an appointment if you don't have digital access; they can generate and hand you the constancia there.
4. Download the resulting PDF, which includes a QR code so the notary can verify its authenticity.

If you don't have an RFC yet or don't remember your password, you'll need to apply for it or recover it first. In those cases, book an appointment at the SAT with your official ID and CURP (Mexico's national population ID code), and check the current requirements directly, as they may vary.

Homoclave and tax regime

Two elements of your constancia often raise questions: the homoclave and the tax regime. Both must be correctly recorded in the deed.

The homoclave

The homoclave is the last few characters of the RFC (usually three). The SAT assigns it to tell apart people with very similar name and birth-date data and to validate the code. Don't make it up or try to work it out: always take it from your official constancia, because a single wrong character invalidates the RFC in the SAT's system.

The tax regime

The tax regime (régimen fiscal) indicates under which rules you pay taxes: salaried employee, business activity, rental income, Régimen Simplificado de Confianza (RESICO), individuals with no economic activity, among others. In a sale, the seller's regime can affect how taxes are calculated and reported, so the notary needs to know it precisely.

How they are used in the closing

During the closing (escrituración), the notary incorporates your tax details into the public instrument that certifies the transaction. If you want to understand the document as a whole, see our guide on what a public deed (escritura pública) is.

In practical terms, the RFC and the constancia are used to:

• Identify buyer and seller by their exact tax ID within the deed.
• Calculate and, where applicable, withhold the ISR owed by the seller on the transfer.
• Issue the digital tax receipts (CFDI) related to the transaction.
• Report the transaction to the SAT with the correct information for both parties.
• Record the tax address and regime exactly as the authority has them registered.

Before closing, it's a good idea to have a sense of the property's market value so you can anticipate the base on which taxes are calculated. You can use our tool to calculate the value of a property and, if you're still searching, explore options in the property search.

Foreigners' cases

Foreigners can also buy and sell property in Mexico, and they also need to identify themselves with the SAT. The situation varies from person to person, so these are general guidelines that you should confirm with your notary and with the authority:

• A foreigner with residency and activities in Mexico usually has an RFC and can generate their constancia just like a Mexican national.
• Someone without an RFC will generally need to obtain one in order to close, presenting their immigration document and whatever requirements the SAT indicates.
• In restricted zones (the border and coastal strip), the purchase is usually carried out through a bank trust (fideicomiso), which adds tax requirements and requirements from the trustee bank.
• The applicable criteria and documents can change, so it is essential to consult the SAT and a notary before starting the transaction.

The general recommendation for any foreigner is to approach the notary's office well in advance: that way the necessary tax procedures are identified in time and the signing isn't held up by a missing document.

Frequently asked questions

Does it cost anything to get the Constancia de Situación Fiscal?

No. The constancia is free on the SAT portal, in its app, or at its offices. Be wary of third parties who charge just to download it.

Do I need an RFC even if I'm only buying?

Generally yes. The notary needs to identify both the buyer and the seller for tax purposes. If you're registered as a person without economic activities, you still need your RFC and a current constancia.

How recent does the constancia need to be?

There is no single rule, but many notary offices prefer a constancia issued recently to make sure the information is still valid. Ask your notary how old a constancia they will accept.

What happens if my tax address has changed?

You must update it with the SAT before closing so that the constancia reflects your actual address. An outdated address can lead to objections and delay the signing.