How the calculations work, and where every number comes from
One calculation engine powers every result on this site, and it reads a single file of official parameters. If you need to defend a figure to an employer, an accountant or a relocation provider, this page shows exactly what was applied.
Official parameters for 2026
No rate or amount is typed into the code or into page text: each comes from the data file, and each was re-read in its official source on October 3, 2026.
| Parameter | Value | Source |
|---|---|---|
| ISR tables (Annex 8) | 11 brackets per table, 1.92 % to 35 % | SAT, Annex 8 to the 2026 Miscellaneous Tax Resolution (DOF 28/12/2025): ISR tariffs |
| Employment subsidy | 15.02% of the monthly UMA = MX$535.65; income limit MX$11,492.66 | DOF 31/12/2025, decree amending the employment subsidy decree |
| UMA (from 1 February) | MX$117.31 daily · MX$3,566.22 monthly · MX$42,794.64 annual | INEGI, press release 1/26: 2026 UMA value |
| General minimum wage | MX$315.04 daily · MX$9,582.47 monthly | DOF 09/12/2025, CONASAMI resolution setting the 2026 general and professional minimum wages |
| Northern border minimum wage | MX$440.87 daily · MX$13,409.80 monthly | DOF 09/12/2025, CONASAMI resolution setting the 2026 general and professional minimum wages |
| Employee IMSS rates | Health surcharge 0.40 % above 3 UMA · cash benefits 0.25 % · pensioners’ medical 0.375 % · disability and life 0.625 % · retirement and old age 1.125 % | Social Security Law (Ley del Seguro Social), current text (Orden Jurídico Nacional) |
| IMSS ceiling | 25 daily UMA = MX$2,932.75 | Social Security Law (Ley del Seguro Social), current text (Orden Jurídico Nacional) |
| Labour-law minimums | Aguinaldo 15 days · vacation premium 25 % · indemnity 3 months + 20 days per year · seniority premium 12 days per year, capped at 2× minimum wage | Federal Labour Law (Ley Federal del Trabajo), current text (Orden Jurídico Nacional) |
| Vacation days | Article 76 table as amended in 2022 | DOF 27/12/2022, decree amending articles 76 and 78 of the Federal Labour Law (paid vacation reform) |
| PTU profit sharing | 10 % of taxable income · individual cap 3 months’ pay or 3-year average | DOF 03/02/2009, Fifth National PTU Commission resolution (10% of taxable income) |
| ISR exemptions | Aguinaldo 30 UMA · vacation premium 15 UMA · PTU 15 UMA · severance 90 UMA per year of service | Income Tax Law (Ley del ISR), articles 93, 95, 96 and 152 (Orden Jurídico Nacional) |
Formulas
Monthly take-home pay
Net = gross salary − ISR withheld − employee IMSS contribution. Loan repayments, housing-credit deductions, alimony and savings schemes are not subtracted, because they are personal.
ISR withholding (article 96, Income Tax Law)
Payroll finds the row of the Annex 8 monthly table whose lower limit is the highest not exceeding taxable income. Tax = fixed amount + (income − lower limit) × rate. Up to MX$11,492.66 a month, the employment subsidy is subtracted, never below zero. A salary equal to the local minimum wage has nothing withheld. All four tables are on the ISR tax brackets page.
Employee IMSS (Social Security Law)
Daily wage = monthly salary ÷ 30. Contribution base (SBC) = daily wage × integration factor, floored at the local minimum wage and capped at 25 UMA. The factor assumes the legal minimum benefits, 1 + (15 + vacation days × 25 %) ÷ 365, which is 1.0493 in the first year. Each branch rate is applied to the SBC over 30.4 days. For a minimum-wage worker the employer pays the employee share (article 36).
Aguinaldo, vacation premium and PTU
Aguinaldo = daily wage × bonus days × days worked ÷ 365. Vacation premium = daily wage × vacation days × premium rate. Individual PTU is split half by days and half by salary, then capped under article 127. In each case the UMA-based exempt part is removed and ISR on the taxable part is shown both ways: the general method (the month’s ISR with and without the payment) and the optional method of article 174 of the Income Tax Regulations.
Finiquito and severance
Finiquito = unpaid wages + pro-rated aguinaldo + pro-rated vacation + vacation premium + seniority premium where due. Severance (liquidación) adds 3 months of integrated daily wage, 20 days per year of service where article 50 applies, and the seniority premium. Separation payments are exempt up to 90 UMA per year of service, more than six months counting as a year; when the payment exceeds one monthly salary, the taxable rest is charged at the effective rate of the last ordinary salary.
Annual return and net to gross
Annual ISR applies the article 152 table to the year’s income minus the deductions you enter. To find the gross salary behind a target net, the engine tests gross figures by bisection until the computed net matches to the centavo, which is how we answer the classic expat question «what gross do I need to take home X?».
Automated tests
The engine ships with a vitest test file arranged in 9 groups, holding 39 individual cases and 2 case tables. They pin the ISR tables at bracket boundaries (monthly, 15-day and annual), the subsidy and its exact cut-off, the minimum-wage rule in both zones, the integration factor and IMSS ceiling, the vacation table year by year, the aguinaldo and its exemption, the vacation premium, PTU capping and sharing, the article 174 method, finiquito and severance with their exemptions, the net-to-gross round trip, and the parsing of numbers typed Mexican-style. They run in the checks that precede every release.
Known limits
- No employer costs. Only employee deductions are shown. Employer IMSS contributions, state payroll tax and other employer charges are not calculated, so this is not a cost-to-company tool.
- No Infonavit. Neither the employer’s housing-fund contribution nor deductions for an Infonavit mortgage.
- No back pay from litigation. Severance excludes salarios caídos, the wages that accrue during a labour lawsuit, which depend on the case.
- 2026 UMA only. The UMA used is the one in force from February to December 2026. January payments used the 2025 value (MX$113.14), so real exemptions were slightly lower.
- Minimum integration factor. Richer benefits raise your real SBC and your IMSS deduction.
- Standard salaried regime only. No fee-based work (honorarios), salary-like income (asimilados), simplified trust regime (RESICO), split payroll abroad, or non-resident taxation. Expatriate packages with housing, school fees or tax equalisation need a professional review.
- One employer, one regular month. Two concurrent jobs and year-end payroll adjustments are not combined.
Results are estimates. They do not replace your e-payslip (CFDI), your employer’s payroll or advice from a Mexican accountant or labour lawyer.
Reviews and corrections
Every parameter is reviewed at least every 12 months and whenever the Official Gazette, the SAT, IMSS, INEGI or CONASAMI publishes a change. If a result differs from your payslip or from an official source, email contact@sueldomx.com with the inputs you used. Each report is checked against the primary source; a confirmed error is fixed in the data or the formula, a test is added so it cannot return, and the page date is updated. The editorial policy sets out the full process.