MX Imss

Section 1 -- Quick Reference

Quick Reference

Field	Value
Country	Mexico
Tax/Contribution	IMSS Social Security (voluntary self-employed)
Currency	MXN only
Primary legislation	Ley del Seguro Social (LSS)
Supporting legislation	Reglamento de la LSS en materia de Afiliacion; Ley del INFONAVIT; Ley del ISR Art. 151
Authority	Instituto Mexicano del Seguro Social (IMSS)
Portal	IMSS Digital (imss.gob.mx)
Filing deadline	Monthly contributions; enrolment at any time
Contributor	Open Accountants Community
Validated by	Pending -- requires sign-off by a Mexican contador publico or social security specialist
Skill version	2.0

UMA Reference Values (2025 -- verify with INEGI)

UMA Reference Values

Item	Approximate Value
Daily UMA	MXN 113.14
Monthly UMA	MXN 3,439.46
Annual UMA	MXN 41,273.52

IMSS Five Branches of Insurance

IMSS Five Branches of Insurance

Branch	Coverage
Enfermedades y Maternidad	Medical care, prescriptions, maternity leave
Invalidez y Vida	Disability pension, death benefits
Retiro, Cesantia y Vejez	Old-age pension, unemployment in advanced age
Riesgos de Trabajo	Work accidents and occupational diseases
Guarderias y Prestaciones Sociales	Daycare, social services

Voluntary Enrolment Options

Voluntary Enrolment Options

Option	Who	Coverage	Key Detail
IVRO (Art. 13)	Self-employed, freelancers	All 5 branches	Total contribution approx. 31-33% of chosen base
Seguro de Salud para la Familia (Art. 240)	Any non-covered person	Health only	Fixed annual cost by age bracket; NO pension
Modalidad 40 (Art. 218)	Former employees with 52+ prior weeks	Pension only (Invalidez y Vida + Retiro)	Total approx. 10.075% of chosen base; max 25 UMA

Conservative Defaults

Conservative Defaults

Ambiguity	Default
Employment status unknown	STOP -- do not proceed
Prior contribution weeks unknown	Assume ineligible for Modalidad 40 until confirmed
Desired salary base unknown	Use 1 UMA (minimum) for estimates
UMA value unconfirmed	Direct client to INEGI for current value

Section 2 -- Required Inputs and Refusal Catalogue

Required Inputs

• Minimum viable inputs — Confirmation of self-employed status, CURP, RFC, and whether currently enrolled in any IMSS regime.
• Recommended inputs — Prior IMSS contribution history (semanas cotizadas), desired salary base for contributions, family members to cover.
• Ideal inputs — Full contribution statement from IMSS, prior year ISR return, INFONAVIT status.

Refusal Catalogue

• R-MX-1 -- Salaried employees — If the client is a salaried employee, the EMPLOYER handles IMSS. This skill covers self-employed/voluntary enrolment only. Stop. (R-MX-1)
• R-MX-2 -- Employer-employee IMSS disputes — Disputes between employers and IMSS regarding contributions or registrations are outside this skill scope. Escalate to a specialist. (R-MX-2)
• R-MX-3 -- Disability claims — IMSS disability benefit claims require medical and legal evaluation. Escalate. (R-MX-3)
• R-MX-4 -- INFONAVIT complex cases — INFONAVIT credit interaction with voluntary IMSS is outside this skill scope. Escalate. (R-MX-4)

Section 3 -- Transaction Pattern Library

This is the deterministic pre-classifier for bank statement lines related to IMSS.

3.1 IMSS Payment Patterns (Debits)

IMSS Payment Patterns (Debits)

Pattern	Category	Treatment	Notes
IMSS CUOTA OBRERO PATRONAL / IMSS PAGO	IMSS contribution	EXCLUDE from business expenses	Personal social security -- ISR deduction (Art. 151)
IMSS REGIMEN VOLUNTARIO / IMSS IVRO	IVRO contribution	EXCLUDE from business expenses	Personal deduction for ISR
IMSS MODALIDAD 40 / IMSS MOD 40	Modalidad 40 payment	EXCLUDE from business expenses	Personal deduction for ISR
IMSS SEGURO SALUD FAMILIA / IMSS SSF	Family health insurance	EXCLUDE from business expenses	Medical expense deduction (limited)
INFONAVIT / INFONAVIT PAGO	Housing contribution	EXCLUDE	Not IMSS; separate programme

3.2 IMSS Benefit Patterns (Credits)

IMSS Benefit Patterns (Credits)

Pattern	Category	Treatment	Notes
IMSS PENSION / PENSION IMSS	Pension income	Taxable income	Report as pension income on ISR return
IMSS INCAPACIDAD / SUBSIDIO IMSS	Disability/sickness benefit	Verify tax treatment	May be exempt up to certain amounts
IMSS REEMBOLSO	IMSS refund	EXCLUDE	Not income

Section 4 -- Worked Examples

Example 1 -- IVRO at Minimum Base (1 UMA)

Input: Self-employed designer, no prior IMSS coverage, wants minimum coverage for self and family.

Reasoning: IVRO at 1 UMA daily (approx. MXN 113.14/day). Monthly base approx. MXN 3,439.46. Self-employed pays both employer and employee shares. Total rate approx. 31% of base. Monthly cost approx. MXN 1,066. Covers all 5 branches including health for family.

Classification: IVRO monthly contribution MXN 1,066. Deductible for ISR purposes under Art. 151.

Example 2 -- Modalidad 40 at Moderate Base

Input: Former employee with 200 weeks prior contributions. Left employment 2 years ago. Chose base of 10 UMA daily.

Reasoning: Eligible for Modalidad 40 (has 52+ weeks, within 5-year window). Daily base: approx. MXN 1,131.40. Monthly base: approx. MXN 34,394.60. Rate: approx. 10.075%. Monthly cost: approx. MXN 3,465. Covers pension only -- NO health coverage.

Classification: Modalidad 40 contribution MXN 3,465/month. Deductible for ISR. Client needs separate health coverage.

Example 3 -- Seguro de Salud para la Familia

Input: Family of 4: 2 adults (age 35, 33), 2 children (age 8, 5). No current IMSS coverage.

Reasoning: Annual cost per person based on age brackets. Adults (19-39): approx. 7.5% of annual UMA each. Children (under 19): approx. 5.9% of annual UMA each. Total annual: approx. MXN 11,061. Health coverage only; no pension.

Classification: Annual family health premium MXN 11,061. Deductible as medical expense (limited).

Example 4 -- Modalidad 40 at Maximum Base

Input: High earner wanting maximum pension. 500 weeks prior contributions. Chose 25 UMA daily.

Reasoning: Maximum Modalidad 40 base: 25 UMA daily = approx. MXN 2,828.50/day = approx. MXN 85,987/month. Monthly cost: approx. 10.075% = MXN 8,663. Maximum pension accumulation strategy.

Classification: Modalidad 40 contribution MXN 8,663/month. Maximum pension strategy. Flag for reviewer to assess long-term pension impact.

Section 5 -- Tier 1 Rules (When Data Is Clear)

5.1 IVRO Contribution Rates (Art. 13, 106, 147, 168, 211)

• IVRO both shares — For IVRO, the self-employed person pays BOTH employer and employee portions. (LSS Art. 13, 106, 147, 168, 211)

IVRO Contribution Rates (LSS Art. 13, 106, 147, 168, 211)

Branch	Total Rate (% of base salary)
Enfermedades y Maternidad (in kind, fixed)	approx. 20.40%
Enfermedades y Maternidad (in kind, excess)	Varies by salary above 3 UMA
Enfermedades y Maternidad (cash)	approx. 1.00%
Invalidez y Vida	approx. 2.375%
Retiro	2.00%
Cesantia en Edad Avanzada y Vejez	approx. 4.375% (increasing under 2020 reform)
Guarderias	1.00%
Riesgos de Trabajo	approx. 0.54% (office/low-risk average)
Approximate total	approx. 31-33%

5.2 Modalidad 40 Contribution Rates (Art. 218)

Modalidad 40 Contribution Rates (LSS Art. 218)

Component	Rate
Invalidez y Vida	approx. 2.375%
Retiro	2.00%
Cesantia y Vejez	approx. 4.375%
Total	approx. 10.075%

• Modalidad 40 maximum base — 25 UMA daily UMA (LSS Art. 218)

5.3 Seguro de Salud para la Familia (Art. 240-245)

Seguro de Salud para la Familia Annual Cost by Age (LSS Art. 240-245)

Age Group	Annual Cost (approx. % of annual UMA)
Under 19	approx. 5.9%
19-39	approx. 7.5%
40-59	approx. 9.1%
60+	approx. 11.9%

• Payment schedule — Payment: annual, upfront. (LSS Art. 240-245)

5.4 Tax Deductibility (ISR Art. 151)

Tax Deductibility (Ley del ISR Art. 151)

Contribution Type	Deductible?
IVRO contributions	Yes -- social security contribution deduction
Modalidad 40	Yes -- deductible for ISR
Seguro de Salud para la Familia	Yes -- medical expense deduction (limited)

5.5 Eligibility Rules

Eligibility Rules

Rule	Detail
IVRO eligibility	Self-employed workers, freelancers, independent professionals
Modalidad 40 eligibility	Minimum 52 weeks prior contributions; must enrol within 5 years of last employer contribution
Seguro de Salud eligibility	Any person not otherwise covered by IMSS

5.6 2020 Reform Impact

• 2020 pension reform impact — The 2020 pension reform gradually increases the employer share of Cesantia en Edad Avanzada y Vejez from 3.15% (2023) to 11.875% (2030). For IVRO, the self-employed pays both shares, so total contribution increases annually through 2030. (Reforma LSS 2020)

Section 6 -- Tier 2 Catalogue (Reviewer Judgement Required)

6.1 Choosing Between IVRO and Seguro de Salud

Freelancer wants health coverage only, no pension. Seguro de Salud is lower cost but accumulates no pension credits. If long-term retirement planning matters, IVRO is required. Flag for reviewer to assess retirement impact.

6.2 Choosing Salary Base for IVRO

Higher base = higher cost but higher pension and maternity/disability benefits. Common strategy: choose a base reflecting actual income for adequate coverage. Flag for reviewer to balance cost vs coverage.

6.3 Modalidad 40 as Pension Strategy

Modalidad 40 allows choosing up to 25 UMA base to maximize future pension. This is a common strategy for persons approaching retirement age. Flag for reviewer -- qualified advisor must assess pension projection.

6.4 Gap in Contributions

If client had employer IMSS, left more than 5 years ago with no contributions since, the Modalidad 40 right has lapsed. IVRO is the only voluntary option.

Section 7 -- Working Paper Template

MEXICO IMSS SELF-EMPLOYED WORKING PAPER
Client: _______________  CURP: ___________  RFC: ___________
Date: ___________

A. CURRENT STATUS
  A1. Employment status                          ___________
  A2. Currently enrolled in IMSS?                ___________
  A3. Prior IMSS weeks (semanas cotizadas)       ___________
  A4. Date of last employer contribution         ___________

B. CHOSEN OPTION
  B1. IVRO / Modalidad 40 / Seguro de Salud     ___________

C. CONTRIBUTION CALCULATION
  C1. Chosen base salary (daily UMA multiples)   ___________
  C2. Monthly base                               ___________
  C3. Applicable rate                            ___________
  C4. Monthly contribution                       ___________
  C5. Annual contribution                        ___________

D. COVERAGE
  D1. Health (Enfermedades y Maternidad)         ___________
  D2. Disability (Invalidez y Vida)              ___________
  D3. Pension (Retiro, Cesantia y Vejez)         ___________
  D4. Work Risk (Riesgos de Trabajo)             ___________
  D5. Childcare (Guarderias)                     ___________

E. TAX DEDUCTIBILITY
  E1. ISR deduction type                         ___________
  E2. Estimated ISR benefit                      ___________

REVIEWER FLAGS:
  [ ] Employment status confirmed (self-employed only)?
  [ ] Prior weeks verified for Modalidad 40 eligibility?
  [ ] 5-year window checked for Modalidad 40?
  [ ] UMA values verified with INEGI?
  [ ] 2020 reform rate adjustments applied?

Section 8 -- Bank Statement Reading Guide

Mexican Bank Statement Formats

Mexican Bank Statement Formats

Bank	Format	Key Fields
BBVA Mexico (Bancomer)	CSV / PDF	Fecha, Descripcion, Cargo, Abono, Saldo
Banorte	CSV	Fecha, Concepto, Retiro, Deposito, Saldo
Citibanamex	CSV / PDF	Fecha, Descripcion, Cargos, Abonos, Saldo
Santander Mexico	CSV	Fecha, Concepto, Cargo, Abono, Saldo
HSBC Mexico	CSV	Fecha, Descripcion, Debito, Credito, Saldo
Scotiabank Mexico	CSV	Fecha, Descripcion, Retiro, Deposito, Saldo

Key IMSS-Related Narrations

Key IMSS-Related Narrations

Narration	Meaning	Classification Hint
IMSS CUOTA / PAGO IMSS	IMSS contribution	Social security -- personal deduction
IMSS MOD 40 / MODALIDAD 40	Modalidad 40 payment	Pension contribution -- personal deduction
IMSS SSF / SEGURO SALUD	Family health insurance	Medical expense deduction
INFONAVIT / PAGO INFONAVIT	Housing fund payment	Separate from IMSS
PENSION IMSS / RETIRO IMSS	Pension receipt	Taxable pension income

Section 9 -- Onboarding Fallback

If the client provides a bank statement but cannot answer onboarding questions immediately:

1. Identify all IMSS-related debits (contributions paid)
2. Classify as personal deductions (NOT business expenses)
3. Flag Modalidad 40 payments separately from IVRO
4. Do NOT assume eligibility for any programme without confirmation

Present these questions:

ONBOARDING QUESTIONS -- MEXICO IMSS SELF-EMPLOYED
1. Are you purely self-employed, or also employed part-time?
2. Are you currently enrolled in any IMSS regime? If so, which one?
3. What is your CURP and RFC?
4. How many weeks have you contributed to IMSS in total (semanas cotizadas)?
5. If you were previously employed, when was your last employer IMSS contribution?
6. Which family members do you want to cover (spouse, children, parents)?
7. What salary base do you want for your contributions?
8. Are you interested in health coverage, pension coverage, or both?

Section 10 -- Reference Material

Key Legislation

Key Legislation

Topic	Reference
IMSS coverage branches	LSS Art. 6, 11
IVRO voluntary enrolment	LSS Art. 13
Modalidad 40	LSS Art. 218
Seguro de Salud para la Familia	LSS Art. 240-245
Contribution rates	LSS Art. 106, 147, 168, 211
ISR deductibility	Ley del ISR Art. 151
UMA usage	Decreto DOF 27/01/2016
2020 pension reform	Reforma LSS 2020 (Cesantia rates)

Known Gaps / Out of Scope

• Employer-employee IMSS obligations
• IMSS disability claims processing
• INFONAVIT credit interaction
• ISSSTE (public sector social security)
• Pension calculation projections (require actuarial analysis)

Changelog

Changelog

Version	Date	Change
2.0	April 2026	Full rewrite to v2.0 structure; bank statement patterns; worked examples
1.0	2025	Initial version

Self-Check

• Employment status confirmed as self-employed?
• Prior IMSS weeks verified before Modalidad 40 recommendation?
• 5-year Modalidad 40 window checked?
• UMA values verified with INEGI for current year?
• 2020 reform rate increases applied?
• Contributions classified as personal deductions (NOT business expenses)?

PROHIBITIONS

• NEVER enrol in Modalidad 40 without verifying at least 52 weeks of prior contributions
• NEVER assume Seguro de Salud para la Familia provides pension or disability coverage -- it is health only
• NEVER use salario minimo for IMSS calculations -- use UMA since 2017
• NEVER ignore the 5-year window for Modalidad 40 enrolment after leaving employment
• NEVER assume IVRO rates are fixed -- the 2020 reform increases Cesantia rates annually through 2030
• NEVER present IMSS calculations as exact -- use the IMSS calculator at imss.gob.mx for precise amounts
• NEVER advise on Modalidad 40 as a pension strategy without flagging for a qualified advisor
• NEVER classify IMSS contributions as business expenses -- they are personal deductions under ISR Art. 151
• NEVER present calculations as definitive -- always label as estimated and direct client to IMSS or a qualified Mexican contador publico

Disclaimer

This skill and its outputs are provided for informational and computational purposes only and do not constitute tax, legal, or financial advice. Open Accountants and its contributors accept no liability for any errors, omissions, or outcomes arising from the use of this skill. All outputs must be reviewed and signed off by a qualified professional (such as a contador publico, social security specialist, or equivalent licensed practitioner in Mexico) before filing or acting upon.

The most up-to-date, verified version of this skill is maintained at openaccountants.com. Log in to access the latest version, request a professional review from a licensed accountant, and track updates as tax law changes.