Mexico ISR Casa Habitación Exemption: The 3-Year Rule

Quick answer: Mexico’s ISR (Impuesto Sobre la Renta, income tax) applies to capital gains on real estate sales, but the law provides an exemption for primary residences that can significantly reduce or eliminate tax on the sale of a home where the seller actually lived. Understanding this exemption, who qualifies, what limits apply, and what documentation is required, is essential for anyone selling Mexico property and for buyers who anticipate selling eventually.

This guide covers the mechanics of the ISR primary residence exemption, the three-year frequency test, cost basis documentation, and the differences between resident and non-resident tax treatment on property sales. For the non-resident seller tax structure, see Mexico Capital Gains Tax for Foreign Sellers. For the role of CFDI receipts in reducing your taxable gain, see CFDI Cost Basis Mexico.

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ISR on Mexico real estate sales: the basic framework

Mexico’s Income Tax Law (Ley del Impuesto Sobre la Renta, or Ley del ISR) treats gains on real estate sales as taxable income. At the time of the notarized closing (escrituración), the notario público calculates and withholds the applicable ISR on behalf of the seller.

The notario’s ISR calculation follows a prescribed methodology:

1. Sale price (precio de enajenación) from the closing escritura
2. Minus deductible cost basis (costo comprobado de adquisición)
3. Minus deductible improvements (mejoras comprobadas con CFDI)
4. Minus notario and closing cost deductions where applicable
5. Equals taxable gain (ganancia)
6. Apply applicable ISR rate or withholding structure
7. Minus applicable exemption if qualifying conditions are met

The result is the ISR withheld at closing. This is a provisional withholding, sellers can file an ISR tax return to adjust the amount if the actual calculation differs from the notario’s provisional figure.

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The primary residence exemption: what the law allows

Article 93 of Mexico’s Ley del ISR provides an exemption from ISR for gains on the sale of a casa habitación (primary residence). The exemption conditions: The exemption is a resident relief and most foreign owners do not qualify for it: it requires Mexican tax residency, an RFC, and documentary proof that the property was genuinely your home, utility bills, bank statements and voter or residency documents in your name at that address. A holiday property visited several weeks a year does not meet the test, whatever the holding period.

Condition 1: Property must qualify as primary residence. The property being sold must have served as the taxpayer’s actual principal place of residence. Investment properties, vacation rentals, and secondary residences do not qualify, even if owned by a Mexican tax resident.

Condition 2: The 700,000 UDI cap applies to the sale price, not to the gain. This is the point most English-language summaries get wrong. Article 93 fracción XIX measures the contraprestación, the consideration received, against 700,000 Unidades de Inversión, the inflation-adjusted unit maintained by Banco de México. If the sale price sits at or below that figure, the entire gain is exempt. If it exceeds it, there is no partial exemption of a first tranche: ISR is determined on the whole gain under Chapter IV of Title IV.

Condition 3: Not used on another home in the previous three years. The test is three years, not five. The taxpayer must not have sold another casa habitación claiming this same exemption during the three years immediately preceding the sale. The limit prevents the exemption from being used on a rapid succession of flips.

Condition 4: RFC and primary residence documentation. To receive the exemption at closing, the seller must present their RFC (tax ID) and documentation demonstrating primary residence status.

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Understanding UDI caps: approximate values

The UDI is Mexico’s inflation-tracking unit of account, with its value published daily by Banco de México. The ISR primary residence exemption limit is defined in UDIs and adjusts with the UDI value over time.

The practical implication for a coastal property: the test is pass or fail on the sale price. A casa habitación sold at or under roughly MXN 6.2 million exempts the whole gain; one sold above it exempts nothing, and ISR is computed on the full gain. Most Riviera Maya and Los Cabos properties owned by foreign buyers sit above the cap, which is a second reason the exemption rarely helps them even where residency is established.

Because UDI values change daily and the cap may be adjusted by legislation, confirm the current applicable cap with a Mexican contador at the time of your sale planning.

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The three-year rule in practice

The three-year frequency test means that if you claimed the primary residence exemption on a Mexico property sale in 2024, your next eligible sale under the same exemption cannot be before 2027. The clock runs from the date of the previous exempt sale, and the notario is the party who verifies it.

Practical implications:

Documentation the notario needs to confirm three-year eligibility:

The notario may request a sworn declaration (declaración bajo protesta de decir verdad) that you have not used the primary residence exemption in the prior three years. False declaration creates legal liability.

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Non-resident seller treatment: a different structure

Foreign buyers who do not establish Mexican tax residency and sell their property at a future date face a different ISR structure: withholding at closing calculated as the lower of two options: A non-resident chooses between 25% of the gross sale price with no deductions and 35% of the documented gain, and the second option requires an RFC and a Mexican legal representative appointed before closing. On a modestly appreciated property the gross method is frequently the larger bill, which is why the choice has to be modelled rather than left to the notario’s default.

Non-residents do not reach the exemption question at all, which is why most foreign owners of Mexican property can stop reading at this section. Without Mexican tax residency and an RFC there is no casa habitación relief available, and the notario withholds at closing under a different structure: broadly 25% of the gross sale price, or up to 35% of the documented net gain where a cost basis built from CFDI invoices is presented. On a $420,000 sale that is $105,000 against roughly $15,750 on a $45,000 documented gain, a difference decided by paperwork rather than by residency.

Option 1: 25% of the gross sale price (without deducting cost basis or expenses)

Option 2: 35% of the net gain (sale price minus deductible cost basis and improvement costs)

The notario calculates both and withholds the lower amount. The seller may then file a Mexican income tax return to adjust if the correct figure differs.

Non-residents can also utilize applicable tax treaty provisions between Mexico and their home country to avoid double taxation on the same gain. The US-Mexico tax treaty is particularly relevant for American sellers.

For a comprehensive treatment of non-resident seller obligations, see Mexico Capital Gains Tax for Foreign Sellers and How to Sell Mexico Property From Abroad.

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Cost basis and the role of CFDIs

Your deductible cost basis is the single most important factor in reducing ISR on a property sale, whether you are a resident claiming the primary residence exemption or a non-resident subject to withholding. Only invoiced costs count. The deed price, ISAI, notario fees and capital improvements documented with a CFDI raise the basis; cash paid to a contractor does not exist for this purpose, however genuine the work. Ten years of improvements without invoices is a five-figure tax difference that cannot be reconstructed at sale.

The deductible cost basis includes:

• Original purchase price as established in your closing escritura
• Notario and closing costs documented at purchase
• Improvement costs documented with CFDI tax receipts from registered contractors

The CFDI (Comprobante Fiscal Digital por Internet) is Mexico’s mandatory electronic tax receipt system. Improvement costs documented with valid CFDIs are deductible from your taxable gain; improvements without CFDIs are generally not deductible. For a full explanation of how to collect and maintain CFDIs for cost basis purposes, read CFDI Cost Basis Mexico.

The practical math: if you purchased a property for USD 300,000 and have USD 50,000 in CFDI-documented improvements, your deductible basis is USD 350,000. Selling for USD 500,000 yields a USD 150,000 gain, not a USD 200,000 gain. ISR applies to the USD 150,000 (with applicable exemptions reducing this further for qualifying residents).

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What happens if documentation is missing at closing

If you arrive at closing without complete documentation, no RFC, missing primary residence proof, or absent CFDI records for improvements, the notario will withhold ISR at standard rates without applying exemptions or deduction adjustments. This is the baseline, not a penalty. The notario is legally required to withhold unless documentation proves otherwise.

Post-closing adjustments are possible through SAT refund processes, but they are time-consuming. Preparing documentation in advance of closing is far more efficient.

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Planning timeline before sale

Selling a Mexico property with optimal ISR treatment benefits from planning 6 to 12 months before the transaction: Six to twelve months is enough to fix what can still be fixed: registering an RFC if you do not hold one, appointing a legal representative, assembling the CFDI file, and obtaining a projection from a Mexican accountant so the notario’s calculation is a confirmation rather than a surprise.

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Comparing resident vs. non-resident tax positions

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What risks should buyers plan for before they commit?

Four misconceptions account for almost every ISR surprise foreign sellers encounter at the notaría, and each of them is a plausible-sounding rule that does not exist. The pattern is the same in all four cases: a buyer hears a simplified version of the exemption from an agent or another owner, plans a sale around it, and discovers at closing that the statute says something different. Because the notario calculates and withholds ISR at the moment of sale, there is no opportunity to restructure once the error surfaces. Read each of the four below against your own assumptions before you list.

Misconception 1: “I’ve owned it for five years so I’m exempt.” Two errors sit inside that sentence. The statutory test is three years rather than five, and it is a frequency limit rather than a holding period: it bars the exemption where you claimed it on another casa habitación in the three years before this sale. No length of ownership triggers the exemption on its own. Primary residence use, Mexican tax residency, an RFC and a sale price at or under 700,000 UDIs are still required.

Misconception 2: “As a foreigner, I don’t owe Mexican tax.” Mexico taxes gains on property located in Mexico regardless of the seller’s nationality or residence status. Non-residents pay a withholding that may differ from resident rates, but the obligation exists.

Misconception 3: “The notario will figure it out.” The notario applies the default withholding unless you provide documentation. They are not your tax advisor and do not proactively seek exemptions on your behalf.

Misconception 4: “Cash sales are not taxed.” Mexico’s notarios are required to report transactions and withhold ISR regardless of the payment method. The ISR obligation follows the transaction, not the payment instrument.

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Summary: the exemption has real value

Mexico’s casa habitación ISR exemption can eliminate capital gains tax for qualifying Mexican tax residents selling their primary home, provided the sale price sits at or under 700,000 UDIs. The three-year frequency test prevents overuse. Documentation, RFC, primary residence proof, CFDI improvement records, delivered at closing is what makes the exemption operational.

Non-residents follow a different withholding structure but have their own optimization levers through cost basis documentation and tax treaty provisions.

For tax ID setup before closing, see Getting an RFC Tax ID as a Non-Resident. For understanding the full Mexico property tax landscape, start with Mexico Property Taxes Explained.

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Buyer scenarios and decision framework

Most foreign owners fall outside this exemption on two independent tests, so read the profiles below for whether you clear both. Mexican tax residency with an RFC and genuine habitual residence is the first; a sale price at or under 700,000 UDIs, roughly MXN 6.2 million, is the second, and most coastal property owned by foreigners sits above it.

Run your own facts through these scenarios before listing, because by notario day the numbers are fixed.

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What checklist should run before you sign?

Four of these five flags are about buying safely. The fifth, missing CFDI on improvements, is the one that decides what the casa habitación exemption is actually worth to you, and it is the only item on this list that cannot be repaired retroactively. Every peso of renovation invoiced without a CFDI in your name is a peso of cost basis you do not have when the notario calculates ISR at sale, and if the sale price exceeds the 700,000 UDI cap the exemption falls away entirely and that basis is all that stands between you and a 35% rate on the gain.

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Frequently Asked Questions

What is the ISR exemption on Mexico property sales? +

Mexico's Income Tax Law provides a capital gains exemption for the sale of a primary residence. Mexican residents who sell their primary residence may be able to exempt a portion of the capital gain from ISR, subject to monetary limits in UDIs and frequency requirements. The exemption applies specifically to Mexican tax residents selling their primary home, not all property sales. Consult a qualified Mexican tax accountant for your specific situation.

Is the ISR casa habitación exemption a five-year rule? +

No, the statutory test is three years, not five. Article 93 fracción XIX bars the exemption where the taxpayer sold another casa habitación claiming it during the three years immediately before this sale. The clock runs from the date of the previous exempt sale, not from the purchase date of the current property, and the notario verifies it through a sworn declaration.

Does the ISR exemption apply to non-residents selling Mexico property? +

Non-residents generally cannot claim the primary residence ISR exemption. Non-residents selling Mexico property typically pay a withholding calculated either as 25% of the gross sale price or 35% of the net gain, whichever is lower, with the notario withholding the lower amount. A tax treaty between your home country and Mexico may affect your ultimate tax liability.

What documents are required to claim the ISR exemption at closing? +

To claim the primary residence exemption at closing, you typically present to the notario: proof of RFC (tax ID), proof that the property was your primary residence (utility bills, credencial de elector, or CURP linked to the address), and CFDI invoices for improvements made during ownership to establish cost basis. Missing documentation results in ISR withholding at full rates.

Can foreigners who are Mexican tax residents claim the ISR exemption? +

Foreign nationals who qualify as Mexican tax residents, generally those who have lived in Mexico for more than 183 days in a calendar year, can potentially claim the primary residence exemption. Mexican tax residency is a legal status determined by SAT criteria, not solely by visa category. Consult a Mexican tax attorney regarding your specific eligibility.

What if the notario withholds ISR and I believe the exemption applies? +

If you qualified for the primary residence exemption but the notario withheld ISR anyway, you can file for a refund through SAT after closing. This requires complete documentation of primary residence use, RFC, CFDI records, and the calculation showing the gain was within the exemption limit. Preparing documentation before closing avoids this scenario.