How to Calculate the Tax Cost Basis of a Property in Mexico

Real examples in Los Cabos — and how to pay less ISR when selling a luxury property

By Yolanda Ramos – Team Leader at Tu Casa Cabo

📍 Introduction: what your property is worth to the tax authority isn’t the same as its market value

When you decide to sell your property in Los Cabos — especially a luxury one — there’s one concept that can mean the difference between paying millions in taxes… or paying a fair amount.

That concept is the tax cost basis.

It’s what the SAT (Mexico’s tax authority) recognizes as your investment in the property — and the higher it is, the less ISR (capital gains tax) you pay when you sell.

🧮 What is a property’s tax cost basis?

The tax cost basis is the sum of all the documented expenses you’ve incurred since you bought the property:

• Purchase price (per the deed)
• Notary and registration fees
• Improvements and remodeling (with a CFDI invoice)
• Buying and selling commissions (invoiced)
• Professional appraisals
• Inflation adjustment (UDIS)

This value isn’t set by the market or a listing website — it’s set by your personal accounting and your invoices.

🏝 Real example: luxury villa in Cabo del Sol

• Purchase price in 2015: $20,000,000 MXN
• Kitchen, pool, and landscaping improvements: $1,800,000 MXN (with invoices)
• Real estate commission (purchase): $600,000 MXN
• Notary and deed fees: $300,000 MXN
• Total initial tax cost basis: $22,700,000 MXN
• Estimated inflation adjustment to 2025 (UDIS): +15% = $26,105,000 MXN

Now let’s say you sell it in 2025 for $32,000,000 MXN.

Your taxable gain would be:

💰 $32,000,000 – $26,105,000 = $5,895,000 MXN
Estimated ISR (e.g. 20%) = $1,179,000 MXN

📌 If you hadn’t documented the improvements and expenses, the ISR would be calculated on a gain of more than $10 million… and you’d pay double.

🏖️ Another case: penthouse in Quivira

• Purchased in 2019: $800,000 USD
• Interior improvements + built-in furnishings: $70,000 USD (with Mexican invoices)
• Commission paid: $48,000 USD
• Notary and trust (fideicomiso) fees: $15,000 USD
• Total tax cost basis: $933,000 USD
• Sale price in 2025: $1,100,000 USD
• Taxable gain: $1,100,000 – $933,000 = $167,000 USD
• Estimated ISR: between 15% and 20% ≈ $25,000 – $33,000 USD

🔍 If you don’t have valid Mexican invoices, your tax cost basis is reduced and the ISR can rise to $50,000+ USD.

📌 What do you need to document your tax cost basis?

• ✔️ Original purchase deed
• ✔️ Electronic invoices (CFDI) for remodeling work
• ✔️ Invoices for commissions and legal services
• ✔️ Proof of notary payment
• ✔️ Professional appraisal (if applicable)

💡 Everything must be issued in your name, in Mexico, in Mexican pesos.

⚠️ Common (and costly) mistakes

• 🚫 Thinking “market value is enough”
• 🚫 Making improvements without invoicing them
• 🚫 Under-declaring the purchase price on the deed
• 🚫 Not keeping legal paperwork from prior years
• 🚫 Not calculating the inflation adjustment

✅ In short: your tax cost basis can be your best defense

Knowing how to calculate and properly document your tax cost basis:

• ✔️ Lets you pay significantly less ISR
• ✔️ Increases your net profit when you sell
• ✔️ Avoids delays and surprises at the notary and with the SAT
• ✔️ Gives you legal protection in case of an audit

👉 At Tu Casa Cabo, we review your case from the start, structure the sale with a tax-smart strategy, and help you optimize your transaction.

📧 Want to know your property’s tax cost basis?

📩 Email us: hola@tucasacabo.com
📅 Book your appointment with Yolanda Ramos: https://calendly.com/yolanda-ramos-tucasacabo/30min