Methodology

KnowPay publishes a Mexico calculator only after the relevant statute, official tariff or government bulletin is read. Calculation engines are pure functions with unit tests. Worked examples on each page call the same engine as the interactive form.

Rules are versioned by country and year. Mexico 2026 constants live in a dedicated module and are never mixed with another country. Peru, Colombia, Chile, Argentina and Spain each have their own 2026 modules. When a source is missing or contradictory, the calculator is labeled as an estimate or left unpublished.

Source priority is: (1) current statute or Diario Oficial, (2) the responsible authority’s official table or bulletin, (3) professional commentary only to locate the primary source. Secondary blogs are not used as the rule.

Annual updates start from the new Anexo 8, UMA, minimum wage and labor reforms. Last-reviewed dates are the research dates, not the URL year.

An estimate means the math is documented but some legally relevant inputs are assumed, excluded or not unique. Payroll providers can still differ on contribution days, exemptions, union contracts and software rounding.

If a result looks wrong, use Contact and name the calculator and rule year. Do not send salaries or other personal amounts unless you choose to.

Finiquito and liquidación headline totals stay gross. Estimated employer ISR withholding uses LISR article 93 fractions XIII and XIV and article 96, sixth paragraph. Article 95 annual tax is not calculated. The XIII exemption uses 90 daily UMA per LISR year of service (a fraction of more than six months counts as a year; exactly six months does not). Prima de antigüedad as a labor entitlement remains capped at two minimum wages.

LISR article 93 XIV treats ordinary compensation (pending salary, vacation pay, aguinaldo and vacation premium) with the documented UMA caps: 30 daily UMA for aguinaldo and 15 daily UMA for vacation premium. Vacation pay and pending salary are treated as ordinary taxable wages.

LISR article 93 XIII still says 90 geographic minimum wages. This product follows the 27 January 2016 desindexación decree and tesis 2029120 and uses 90 daily UMA. That is an interpretive choice and is labeled as such.

LISR article 95 describes annual tax on certain separation payments. KnowPay does not compute article 95. Employer withholding follows article 96, sixth paragraph: if the taxable excess is below the last monthly salary, the monthly Anexo 8 table is applied without subsidy; otherwise the last monthly ISR-with-subsidy rate is applied to the taxable excess. Individual facts can change the final annual liability.

UMA comes from INEGI. The 2026 daily UMA is 117.31 from 1 February 2026; January 2026 still uses the 2025 UMA. Labor entitlements stay independent from this tax estimate.