ISR Retention Selling a Baja Condo: Percentage Guide for American Sellers

When an American sells a condominium in Baja California—whether in Ensenada, Rosarito, or Cabo—Mexico's tax authority (SAT) collects income tax through a retention (withholding) that the notario público deducts from the sale proceeds at closing. The percentage depends on which calculation method the seller qualifies for and chooses.

This article explains the two ISR retention rates, how each is calculated, what documentation you need, and how the retention affects your overall return on a Baja California investment like Panorama by Viento.

The Two ISR Retention Methods

Mexico's ISR Law (Ley del ISR, Article 160) gives non-resident sellers a choice between two methods. You apply the one that results in the lower tax liability, provided you have the documentation to support it.

Method 1 — 25% of Gross Sale Price

Rate: 25% applied to the full consideration received.

Documentation required: None beyond the sale deed itself.

When it applies by default: When the seller cannot or does not provide cost basis documentation, or when they simply elect this method.

Example:

• Sale price: $480,000 USD
• ISR retention (25%): $120,000 USD
• Net to seller before other costs: $360,000 USD

Method 2 — ~35% of Net Gain (Indexed)

Rate: Non-resident rate applied to the net gain. The effective rate under current law is around 30–35% of the calculated gain.

How the net gain is calculated:

1. Start with the original acquisition cost
2. Apply the INPC inflation index (official Mexican CPI factor) to adjust the original cost for inflation
3. Add qualifying capital improvements (certified by a licensed perito valuador)
4. Subtract this adjusted basis from the sale price
5. Apply the tax rate to the result

Documentation required:

• Original fideicomiso deed with purchase price
• Closing statement from original acquisition (estados de cuenta from notario)
• Capital improvement receipts with appraiser certification
• Seller's RFC (Mexican tax ID)—often required by notarios for Method 2

Example (same property):

• Sale price: $480,000 USD
• Original cost: around half a million USD
• INPC-indexed cost (assume 12% cumulative inflation over 4 years): $436,800 USD
• Certified improvements: $25,000 USD
• Adjusted basis: $461,800 USD
• Net gain: $18,200 USD
• ISR at ~35%: ~$6,370 USD
• Net to seller before other costs: ~$473,630 USD

The difference in this example: Method 1 costs $120,000; Method 2 costs ~$6,370. The gap is nearly $114,000.

Why the Documentation Matters So Much

The core reason Method 2 is dramatically lower is that most buyers at pre-sale prices acquire their property well below future market value. The cost basis—your original purchase price, adjusted upward for inflation and improvements—is the key variable. Without documentation, the notario cannot legally apply Method 2.

Most common documentation failures:

• Original deed is lost or left with an intermediary who is no longer accessible
• Closing statement was never provided or was discarded
• Improvement invoices were informal and lack RFC numbers
• RFC was never obtained, preventing Method 2 in some notarial offices

Prevention:

• At closing, ensure you receive the original escritura (deed) or certified copy
• Scan every closing document and store securely in the cloud or with your US attorney
• Obtain an RFC from Mexico's SAT within the first year of ownership—even if you have no other Mexican tax obligations
• Have improvements certified by a licensed Mexican appraiser contemporaneously, not years later

Obtaining an RFC as a Foreign Property Owner

The Registro Federal de Contribuyentes (RFC) is Mexico's tax identification number. Americans who own Mexican property are not automatically required to register—but having an RFC enables Method 2 and is increasingly required by banks and notarios.

To obtain an RFC:

1. Obtain a Temporary Resident visa (FM3) from INM, or use your existing immigration document
2. Present passport, immigration document, proof of address in Mexico, and CURP (if assigned)
3. Visit your local SAT office or hire a Mexican CPA to complete the registration online
4. The process typically takes 1–3 weeks

The annual compliance burden with just an RFC and no Mexican taxable income is minimal.

The INPC Inflation Adjustment: A Hidden Benefit

One often-overlooked advantage of Method 2 is the INPC inflation adjustment. Mexico experiences meaningful inflation, and the indexed adjustment to your original cost can be significant over a multi-year holding period. A property purchased for around half a million USD in 2022 might have an INPC-adjusted basis of $440,000–$460,000 by 2027 even without any physical improvements, simply due to the official inflation factor.

This indexed basis increase further reduces the net gain subject to ISR.

Impact on Your Total Return

For buyers of Viento who enter at pre-sale pricing and plan to hold for 5–10 years, the ISR retention is a meaningful component of the total return analysis. Modeling the after-tax return requires:

• Estimated future sale price
• INPC-adjusted original cost at time of sale
• Any documented improvements
• The prevailing non-resident ISR rate at time of sale

Our team works with bilingual financial advisors who can model this scenario specifically for the units available at Panorama by Viento (from around half a million USD). The after-tax return picture is an important part of any serious investment conversation.

US Foreign Tax Credit: The ISR Is Not Wasted

For American sellers, the ISR withheld in Mexico is not money lost twice. It qualifies as a creditable foreign tax on Form 1116 of your US federal return. For most sellers, the Mexican ISR (even Method 2) equals or exceeds the US federal capital gains tax owed on the same gain, effectively eliminating additional US tax liability.

For a complete picture of your US tax obligations on the sale, see our guide on selling Baja California property as a US citizen.

To discuss the investment case and tax structure for a specific residence at Panorama by Viento, contact our team to schedule a private site visit at Km 104 Carretera Tijuana–Ensenada. We are available via WhatsApp and welcome buyers from San Diego and beyond.