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Mexico · Process · Updated December 2026

Capital Improvements on Mexican Property: Tracking Guide

Track capital improvements on Mexico property with facturas (CFDI) and an RFC. Skip the paperwork now and pay 35% on the upgrade later.

By the CrossingHQ Editorial Team

Track every capital improvement with a proper factura (CFDI) tied to your RFC, or pay roughly 35% of the upgrade in ISR when you sell. That's the whole article in one sentence. Capital improvements add to your cost basis on the US or Canadian side, and properly invoiced improvements can also reduce your Mexican ISR at closing. Skip the documentation and the notario público has nothing to deduct.

Foreign owners holding property in Mexico for several years almost always spend real money on improvements. Restoring older Centro Histórico inventory, modernizing dated condo finishes, building out beach-property infrastructure, adding amenities. Each of those dollars can reduce the eventual capital-gains tax bill on both sides of the border, but only if the paperwork lines up.

Inadequate tracking is one of the most common preventable causes of overstated capital gains at sale. Buyers who don't keep a basis ledger from acquisition forward often discover at sale that years of work cannot be substantiated, producing higher US, Canadian, and Mexican tax exposure than necessary.

What counts as capital improvement vs. operating expense

The basis-vs-expense distinction matters on both sides of the border. The treatment is broadly similar under US, Canadian, and Mexican tax law:

Capital improvements (basis additions) — items that add value, extend useful life, or adapt to new uses:

Operating expenses (current-year only) — items that maintain rather than improve:

The capital-vs-expense line is fact-specific in many cases. For ambiguous items, consult cross-border tax counsel rather than self-classifying.

The CAD/USD conversion framework

For US persons, capital improvements get added to USD basis at the USD-equivalent on the date the improvement is incurred (the date the contractor was paid, the materials were purchased). Each transaction needs:

For Canadian persons, the parallel CAD framework: capital improvements added to CAD ACB at CAD-equivalent on the date incurred.

For a typical scenario — Canadian buyer who acquired a Mérida home in 2019 and undertook a $100,000 USD-equivalent kitchen-and-bath renovation in 2022 paid in pesos:

Without contemporaneous documentation, this calculation gets harder to substantiate as years pass.

The basis-ledger framework

Maintain a basis ledger — a simple spreadsheet tracking acquisition cost plus all capital-improvement additions over the holding period. Each entry should include:

Keep the ledger from acquisition forward, with all source documentation (contractor facturas, materials receipts, bank statements showing payment, exchange-rate documentation) in an organized digital archive.

For owners with substantial improvement spending, ledger maintenance is real work — typically 30 to 90 minutes per major entry to document properly. The investment is repaid at sale with accurate basis substantiation.

Documentation requirements for cross-border tax

US and Canadian tax authorities require documentation supporting basis claims if an audit is initiated. For improvements on Mexican property:

Retain documentation for the holding period plus the statute-of-limitations period (typically 3 to 7 years post-sale depending on jurisdiction and circumstances). A digital archive with cloud-based backup is the standard.

Mexican-side ISR at sale: where the documentation actually pays you back

When you sell, the Mexican-side tax framework runs in parallel to your US or Canadian filing, and the documentation rules are stricter. This is the part most foreign buyers discover too late.

ISR at closing is collected by the notario público. The notario calculates and remits the capital-gains withholding to SAT directly out of closing funds. ISR is calculated against your Mexican-side recorded basis, which is often lower than your true USD or CAD basis because peso-denominated improvements were never recorded on the Mexican side at all.[SAT, LISR Artículo 126 (notario público withholding on enajenación de inmuebles), 2026-04]

The 25% gross vs. 35% net election. Foreign sellers without an RFC and Constancia de Situación Fiscal generally face a flat 25% withholding on the gross sale price under Article 126. Sellers with an RFC who file the proper documentation may elect to be taxed on net gain at progressive rates that top out around 35%, with deductions allowed for documented improvements. Net often beats gross when you have real basis to deduct, but only if your facturas are clean.[SAT, LISR Artículo 121 (deducciones autorizadas — inversiones en construcciones, mejoras y ampliaciones), 2026-04]

RFC and Constancia de Situación Fiscal. To elect net taxation and deduct improvements, you generally need:

The notario rejects facturas that don't match. If the RFC on the factura doesn't match the seller's RFC, or the factura is missing CFDI structure, or payment isn't traceable, the notario will not deduct it. The improvement effectively didn't happen for ISR purposes. This is the failure mode that catches foreign sellers most often — they kept the receipts, but the receipts were issued to a contractor friend or a generic "público en general," not to the owner's RFC.

The Mexican-side ISR calculation and the US or Canadian capital-gains calculation are separate. Your US or Canadian basis ledger is for home-country tax. Your Mexican-side basis is for ISR. Both matter at sale. Track both.

Capital improvements that affect FX-translation at sale

A subtle but important consideration on the home-country side: capital-improvement basis additions are converted to USD or CAD at the date-of-expenditure FX rate, not the date-of-sale FX rate. A peso-funded improvement made when the peso was stronger (18:1 USD/MXN) produces a higher USD-basis addition per peso spent than the same improvement made when the peso was weaker (22:1).

For US sellers calculating capital gain at sale:

The mixed-FX-rate calculation produces basis amounts that reflect actual USD spending across the holding period. For Canadian sellers, the parallel CAD framework with CAD/MXN rates at each date.

Common scenarios for Mexican property

Restored Centro Histórico inventory (Mérida, San Miguel, Mexico City colonial neighborhoods): substantial improvement spending typical at acquisition — restoring structural elements, electrical and plumbing systems, kitchen and bath modernization. Total improvements often equal 30% to 100% of acquisition price. Documentation rigor is essential.

Tulum/Cabo coastal condo modernization: typical post-acquisition spending on furniture upgrade, finish modernization, and occasionally HOA-special-assessment contributions to building-level capital improvements. HOA special-assessment payments are generally NOT directly basis additions for the individual unit — they fund building-level work that affects the building's overall value rather than the individual unit's specific basis.

Mexico City Roma/Condesa older-building modernization: substantial spending on restored apartments — kitchen, bath, finish modernization, and sometimes structural and electrical upgrades for older buildings.

Beach-property infrastructure upgrades (Cabo, Vallarta, Tulum): hurricane-shutter installation, generator installation, water-supply infrastructure (cistern upgrades, filtration systems), solar installation. These typically qualify as capital improvements.

Where buyers commonly stumble

Cash-paid work without facturas. In Mexico, some contractor work is cash-paid without a formal CFDI. Without a factura tied to your RFC and traceable payment, the basis addition is difficult to substantiate at audit on the home-country side and won't be deducted on the Mexican side at all. Insist on CFDI facturas with your RFC for all substantial work.

Mixing capital-improvement and operating-expense classification. Some items are clearly capital (room addition); others clearly expense (paint refresh); plenty are ambiguous (kitchen-counter replacement could be either depending on scope). Misclassification produces either overstated current-year deductions or understated basis. Engage cross-border tax counsel for ambiguous items.

Failing to convert peso amounts to home-country currency contemporaneously. Years later, reconstructing the FX rate on each historical payment date is tedious and error-prone. Convert each transaction to USD or CAD at the time of expenditure and record it in the basis ledger.

Your next step

Start a labeled folder today, even if you only own one property and haven't done anything to it yet. The five-item starter checklist:

  1. Get your RFC and current Constancia de Situación Fiscal (or confirm yours is current). Without these, you cannot elect net ISR taxation or deduct improvements at sale.
  2. Open a digital folder named for the property, with subfolders for each tax year.
  3. Start the basis ledger spreadsheet — even one row for the acquisition cost gets the system going.
  4. Tell every contractor up front: CFDI factura with your RFC, traceable payment, no exceptions on substantial work.
  5. Save before-and-after photos with dates for any work above a few thousand dollars.

For monthly reads on cross-border tax dynamics and FX-rate movements that affect basis tracking, the /newsletter covers what's worth tracking.

For broader Mexico transaction mechanics, see /mexico/how-to-buy-property/ and /mexico/closing-costs/. For the US tax framework, /mexico/taxes-american-buyers/. For the Canadian tax framework, /mexico/taxes-canadian-buyers/. For broader Canadian foreign-property treatment, /canadians/buying-property-abroad/.

Disclaimer

This article is for informational purposes only and does not constitute legal or tax advice. Capital-improvement basis tracking involves federal civil code, state-level Mexican tax framework, plus US or Canadian tax framework on foreign-property basis. Engage a cross-border tax advisor for capital-improvement classification and documentation. CrossingHQ does not provide tax preparation, advice, or representation services.

Current as of 2026-12-30. We review legal content quarterly and update on rule changes. To report an error, contact us.

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