Aguinaldo and ISR: what remains after SAT
The statutory aguinaldo is 15 days of pay (LFT art. 87). For income tax, LISR article 93, section XIV exempts up to 30 UMA. With the 2026 daily UMA of $117.31 (INEGI), the exempt cap is $3,519.30.
Quick answer
Wage $10,000 → gross aguinaldo $5,000. Exempt $3,519.30, taxable $1,480.70, estimated ISR $161.10, net $4,838.90.
Educational estimate
Withholding uses the difference in monthly ISR (Anexo 8) between wage + taxable portion and wage alone. It is not your payroll file and does not include employment subsidy.
Full-year gross
Aguinaldo = (monthly salary ÷ 30) × 15
Taxable portion
Taxable = max(0, aguinaldo − 30 × daily UMA)
Example $10,000 (default)
| Item | Amount |
|---|---|
| Gross (15 days) | $5,000.00 |
| 30 UMA exemption | $3,519.30 |
| Taxable | $1,480.70 |
| ISR on aguinaldo | $161.10 |
| Net | $4,838.90 |
2026 salary scenarios
| Monthly wage | Gross | ISR | Net |
|---|---|---|---|
| $6,000 | $3,000.00 | $0.00 | $3,000.00 |
| $8,000 | $4,000.00 | $52.30 | $3,947.70 |
| $10,000 | $5,000.00 | $161.10 | $4,838.90 |
| $15,000 | $7,500.00 | $763.11 | $6,736.89 |
| $20,000 | $10,000.00 | $1,384.28 | $8,615.72 |
Exempt cap vs trap
| Idea | Figure | Meaning |
|---|---|---|
| 2026 daily UMA | $117.31 | INEGI base for the cap |
| 30 × UMA | $3,519.30 | LISR 93-XIV exempt |
| Trap “all taxable” | ISR on full $5,000 | Ignores the $3,519.30 exemption |
| Correct $10k model | ISR $161.10 | Only on $1,480.70 taxable |
If gross pay does not exceed $3,519.30 (for example $6,000/month → $3,000 aguinaldo), this model withholds no ISR.