IMSS pension simulator: Ley 73, Ley 97 and Modalidad 40

The rule is a date. The current Social Security Law (LSS) came into force on July 1, 1997 and at that moment repealed the law published on March 12, 1973 (First Transitory Article). If you were registered with the IMSS before that date, even if you contributed only a few weeks in a summer job, you belong to the transition generation: when you meet the requirements you can choose to retire under the former law or the current one (Third and Eleventh Transitory Articles). If your first registration was on or after July 1, 1997, only Ley 97 applies to you, with an individual account at an AFORE.

Your registration date appears on your statement of contribution weeks. It does not matter how long you stopped contributing or how many times you changed jobs: what gives you the right to choose is having been registered before the change in law. The Fourth Transitory Article requires the IMSS, on request, to estimate your pension under both regimes so you can decide.

Almost everything changes between the two: who pays, how it is calculated and how much you need to contribute.

The simulators use these values. All of them come from official publications or from the law itself and are dated; if you read this page in 2027, remember that the UMA changes every February and the minimum wage every January.

The vejez or cesantía en edad avanzada (old-age unemployment) pension under the 1973 law consists of a basic amount and annual increments for every 52 weeks contributed after the first 500 (Article 167). Both are percentages of the average daily salary over the last 250 weeks, and they depend on the salary group: that average is expressed as a multiple of the general minimum wage in force on the date you retire. Those who earn little receive a high basic amount (80% of salary if they earn up to one minimum wage) and small increments; those who earn more than six minimum wages receive a 13% basic amount, but 2.45% for each additional year.

Fractions of a year also count: 13 to 26 leftover weeks earn half an increment and more than 26 earn a full one. The cesantía factor by age is then applied to the vejez pension, from 75% at age 60 to 100% at 65. Next come the family allowances of Article 164: 15% for a wife or common-law partner and 10% for each child under 16 (or up to 25 if studying, with no limit if disabled); if there is no wife and no children, 10% for each parent financially dependent on the pensioner, and if there are none of these, a 15% assistance supplement. The IMSS adds a 10% assistance supplement when the pensioner has only one dependent parent.

Two limits close the calculation. Article 168 sets a floor: the pension, including allowances, cannot be less than one general minimum wage. Article 169 sets a ceiling: it cannot exceed 100% of the average salary used as its basis. Finally, the Fourteenth Transitory Article of the decree published in the DOF on December 20, 2001 (amended on January 5, 2004) multiplies by 1.11 the pensions of those aged 60 or older who receive at least one minimum wage; that is why the 2026 minimum pension is $315.04 × 365 ÷ 12 × 1.11 = $10,636.53. Article 167 also grants a year-end bonus (aguinaldo) equal to one monthly payment.

The salary cap: 25 times, 10 times or 25 UMA. Article 33 of the 1973 law, as amended in 1993, set a general limit of 25 minimum wages on the contribution salary, but 10 for the disability, old-age, cesantía and death insurance branches. The Second Chamber of the Supreme Court held in case law 2a./J. 85/2010 that the average salary over the last 250 weeks is capped at 10 minimum wages, a holding reaffirmed in 2a./J. 164/2019, published on January 24, 2020. The IMSS, however, keeps the cap at 25 minimum wages: its Technical Council unanimously ratified it on February 6, 2020. The simulator uses 25 by default and lets you switch to 10.

In practice there is a third limit that now matters more. Since the constitutional deindexation reform (DOF, January 27, 2016), references to the minimum wage as a unit of measure are read as references to the UMA, and the IMSS caps the contribution base salary at 25 UMA. Because the minimum wage has grown faster than the UMA, in 2026 the contribution cap is $2,932.75 a day, below even 10 minimum wages ($3,150.40). Anyone who contributed at the cap in their last five years will have an average below either of the two limits in the court debate. By contrast, the minimum wage, not the UMA, is used to determine the salary group and the minimum pension; a collegiate court held that the UMA cannot be applied to calculate pension increments (isolated thesis I.6o.T.170 L, 2019).

Modalidad 40 is voluntary continuation in the mandatory regime. It is now governed by Article 218 of the current law: anyone with at least 52 contribution weeks in the last five years who has left covered employment can keep contributing on their own to the disability and life and the retirement, cesantía and vejez insurance branches, registered with their last salary or a higher one, paying monthly in advance. The right is lost if it is not requested in writing within five years of leaving covered employment (Article 219), and enrollment ends, among other reasons, if you miss two monthly payments (Article 220).

For someone under Ley 73, the appeal is arithmetic. The pension depends on the average of the last 250 weeks, so contributing for about five years on a high salary replaces that average, and every week paid also adds increments. The salary that can be registered is capped at 25 daily UMA, $2,932.75 in 2026, equivalent to 9.31 minimum wages: it falls in the highest group of the Article 167 table.

The cost, however, has changed. In Modalidad 40 you pay the full employer and employee contributions: retirement (2%), employee cesantía and vejez (1.125%), disability and life (1.75% employer and 0.625% employee, Article 147) and pensioners’ medical expenses (1.05% and 0.375%, Article 25), which add up to a fixed 6.925%, plus the employer cesantía and vejez contribution, which the 2020 reform raises every year until 2030. For salaries of 4.01 UMA and above, the total rate goes from 13.347% in 2025 to 14.438% in 2026 and will reach 18.800% in 2030.

Under Ley 97 the pension is funded by your individual account balance. To qualify for a cesantía pension you need to be 60, and 65 for vejez (Articles 154 and 162), and in both cases the weeks set by the Fourth Transitory Article of the reform published in the DOF on December 16, 2020: 750 in 2021, 25 more each year, 875 in 2026 and 1,000 from 2031. If you reach the age without the weeks, you can withdraw your balance as a lump sum or keep contributing; with at least 750 weeks you keep medical coverage. If you never used your housing loan, the balance of that subaccount is transferred to the AFORE to purchase the pension (Article 40 of the INFONAVIT Law).

There are three contributions to the retirement, cesantía and vejez subaccount: 2% for retirement paid by the employer, 1.125% for cesantía and vejez paid by the employee, and the employer cesantía and vejez contribution, which since 2023 depends on salary and rises every year until 2030 (Article 168 and Second Transitory Article). For those earning up to 4 UMA, the Federal Government also deposits a social contribution per day contributed, indexed quarterly to the INPC. A 2026 detail: because the minimum wage ($315.04) equals 2.69 UMA, the bracket from 1.01 minimum wages to 1.50 UMA is empty in practice, and someone earning a little over the minimum contributes in the 2.51 to 3.00 UMA bracket.

How the balance becomes a pension. On retirement you choose between a life annuity, which you buy from an insurer and which pays you for life, and a programmed withdrawal, which the AFORE recalculates each year from your balance and your life expectancy. In both cases the monthly amount is, in essence, the balance divided by an annuity factor: the present value of paying one peso a month for as long as you live. The simulator calculates it with the CNSF’s EMSSA-15 table and its improvement factors, at the real rate you choose, and presents it as an approximation: an actual life annuity also includes survivors’ insurance for your beneficiaries and the insurer’s expenses, which reduce the amount.

Guaranteed pension. If your balance falls short, the State guarantees a minimum pension that, since the 2020 reform, depends on three variables: your age, your weeks and your career average salary, adjusted for inflation and expressed in UMA (Article 170). The statutory table is in 2020 pesos and is indexed every February with the INPC; with the cumulative factor of 1.3503, its 2026 values range from about $3,540 to $11,128 a month. The week columns shift every year: in 2026 the first corresponds to 875 weeks and the last to 1,125 or more. If your calculated annuity exceeds by more than 30% the guaranteed pension you would be entitled to at age 60, you can retire before that age (Article 158).

Top-up from the Fondo de Pensiones para el Bienestar (Pension Fund for Wellbeing, the Bienestar Fund). The decree published in the DOF on April 30, 2024 provided that the Fund, administered by Banco de México as trustee, would pay out resources so that workers aged 65 or older whose pension is equal to or below a threshold receive a top-up up to their last salary, without exceeding that threshold. The threshold started at $16,777.68 a month, equal to the average salary registered with the IMSS in 2023 adjusted for estimated 2024 inflation, and it is updated every January 1. For 2026 it is $17,885.85. According to the IMSS, it applies to those who began contributing on or after July 1, 1997, are 65 or older when claiming the vejez pension, meet the weeks required for the year (875 in 2026), have a resolution issued on or after May 2, 2024 and receive a pension below the average salary of their last year of contributions; under a life annuity, they must not have withdrawn surplus funds from the account. The IMSS assesses it automatically and reported 7,224 beneficiaries between 2024 and May 2026. The top-up is subject to the Fund’s sufficiency.