Every year-end, payroll teams face the same question: how much aguinaldo does each employee get, and how much tax should be withheld? The aguinaldo is Mexico's mandatory year-end bonus. The basic rule is simple: it must be paid no later than December 20 and can never be less than 15 days of salary.
Step by step
- If the employee worked the whole year: multiply the daily salary by the number of aguinaldo days your company grants (at least 15).
- If the employee joined during the year or left early: pay the pro-rated amount: daily salary × aguinaldo days × days worked ÷ 365.
Example: an employee earns $400 per day and the company grants 15 days. For a full year, the aguinaldo is $6,000 ($400 × 15). If the employee worked only 200 days, the amount is $3,287.67 ($6,000 × 200 ÷ 365).
Income tax (ISR) treatment
ISR is Mexico's federal income tax, withheld by the employer through payroll. The UMA (Unidad de Medida y Actualización) is the official reference unit used to set tax and social security limits.
- The exempt portion is up to 30 UMA per year, which in 2026 equals $3,519.30.
- The exemption is annual and is used up over the year: if part of the aguinaldo was paid earlier, that amount counts toward the same limit.
- For the taxable portion there are two options: add it to the month's salary and apply the Article 96 tax table, or use the procedure in Article 174 of the ISR Regulations, which usually results in lower withholding.
Social security (IMSS)
IMSS is the Mexican Social Security Institute. Aguinaldo days are part of the integration factor used to determine the contribution base salary (salario base de cotización). If your company grants more than 15 days, the factor goes up.
Things to watch
- Check the days worked for every pro-rated case, especially new hires and terminations during the year.
- Keep track of the exemption already used if you pay aguinaldo advances.
- Choose the withholding method before calculating and apply it consistently.
Legal basis
- Federal Labor Law (Ley Federal del Trabajo), Article 87.
- ISR Law, Article 93, section XIV, and Article 96.
- ISR Law Regulations, Article 174.
In Nomikhor, the aguinaldo runs as an extraordinary payroll: the system calculates pro-rated amounts, splits taxable and exempt income, computes ISR with up-to-date tax tables and UMA values, and stamps the CFDI payroll receipts (Mexico's electronic tax receipts) with unlimited stamping.