Glossary · 2 min read
IMSS contributions: what they are and who pays them
Short answer
Employer and employee contributions are the payments to the IMSS that fund social security. The company pays one part and the other is withheld from the worker. They are calculated on the contribution base salary.
Which insurances they cover
- Workplace risks.
- Illness and maternity.
- Disability and life.
- Retirement, unemployment in old age and old age.
- Daycare and social benefits.
What they depend on
They depend on the contribution base salary, the UMA and each company's risk premium. The percentages change by branch and by year, so calculate them with your accountant or in the IMSS system.
Why everything starts with the working-time record
Almost every labor calculation starts from the same data point: how many hours and which days each person worked. If that data is uncertain, so is everything else.
- Overtime: it is paid according to the hours of each week.
- Sunday premium and rest days worked: they depend on which days were worked.
- Aguinaldo and profit sharing: they use the days worked in the year.
- Labor lawsuits: the company must prove the working time.
Since 2026, the Federal Labor Law requires that record to be electronic, per person, with start and end time.
Common mistakes
- Using the UMA or minimum wage value from a previous year.
- Confusing daily salary, integrated salary and contribution base salary.
- Calculating benefits without knowing the days actually worked.
- Taking the legal minimums as if they were the maximum.
- Not keeping the backup of the calculation.
What to do now
- Confirm the current value for the year.
- Have each person's daily salary at hand.
- Check the days and hours worked in your record.
- Do the math and keep it.
- Validate it with your accountant.
Related terms
What is NOM-035. NOM-035 is the STPS standard that requires identifying and preventing psychosocial risk factors at work, such as excessive workloads and long workdays.
What is the contribution base salary (SBC). The contribution base salary is the salary used to calculate IMSS contributions and INFONAVIT contributions.
Overtime: what it is. Overtime is the hours worked above the ordinary workday.
Frequently asked questions
Do IMSS contributions go down with the 40-hour workweek?
Not by themselves: salary does not go down.
Where does the data come from?
From the Federal Labor Law and from the official values published by INEGI and the National Minimum Wage Commission.
Do these values change every year?
Yes. The UMA is updated every February 1 and the minimum wage every January 1. Always confirm the current value.
Are the amounts gross or net?
Gross. They do not account for taxes or social security contributions.
Can I use this for my payroll?
It works as a reference. Your accountant should do or validate the payroll calculation.
Legal basis and sources
- Social security: Social Security Law and INFONAVIT Law.
- Decree amending the Federal Labor Law on the reduction of the working week. Official Gazette of the Federation, May 1, 2026.
- Federal Labor Law, current text. Chamber of Deputies.
How we write this content. The Sicheca team writes it from the official text of the law. When something is not yet defined by the authority, we say so. It is general information and does not replace the advice of a lawyer or an accountant.