Common Mistakes When Filing Income Tax (ISR) and How to Avoid Them

Apr 20
1 min read

Filing your Income Tax (ISR) properly is a responsibility that every taxpayer in Mexico must fulfill. However, mistakes are common—and they can lead to fines, interest charges, or even tax audits by the SAT.

Here are the most frequent errors people make when filing ISR—and how to avoid them:

1. Not reporting all income

Some taxpayers leave out income—whether accidentally or unknowingly. The SAT can cross-check your information and detect inconsistencies.

Solution: Keep your accounting organized and up to date. Use digital tools or hire a professional accountant.

2. Incorrect or unsupported deductions

Claiming deductions that are not allowed or not properly documented is a common issue.

Solution: Make sure your deductions are supported by valid electronic invoices and fall under your correct tax regime.

3. Filing late

Missing the deadline leads to penalties, interest, and sometimes larger consequences.

Solution: Keep a tax calendar and work with a CPA to stay ahead of deadlines.

4. Trusting SAT’s pre-filled data without review

Relying solely on the SAT’s pre-filled information can lead to errors if any data is outdated or incorrect. Solution: Review every section carefully before submitting your return.

At ISTAXPRO, We Handle It All for You

Tax season doesn’t have to be stressful. At ISTAXPRO, we offer personalized tax support so you can file your ISR correctly, on time, and with peace of mind.