Cohabitation Agreement Mexico (Acuerdo de Unión Libre / Concubinato)

A Cohabitation Agreement Mexico (Acuerdo de Unión Libre / Concubinato) is a formal written document through which two unmarried partners who live together in a stable and permanent union in Mexico — known as concubinos — formally record the terms of their cohabitation arrangement and exercise the legal rights and obligations that arise from concubinato under the Código Civil Federal (CCF) Articles 291-Bis through 291-Quater and the equivalent provisions of state civil codes. The concubinato is a legally recognized family institution in Mexico, generating rights and obligations between the partners that are distinct from but in some respects comparable to those arising from marriage, including rights to alimentos (support), inheritance (sucesión legítima), and in several states, community property over assets acquired during the union.

The constitutional recognition of concubinato as a protected family institution derives from Article 4 of the Constitución Política de los Estados Unidos Mexicanos, which protects the integrity and legal organization of the family without restricting that protection to the formal marriage relationship. The Suprema Corte de Justicia de la Nación (SCJN) has developed an extensive body of jurisprudencia since the 1990s recognizing concubinato rights — including landmark decisions establishing that concubinos have the same inheritance rights as spouses in intestate succession (sucesión legítima) and the same rights to IMSS survivor benefits (pensión por viudez) under the Ley del Seguro Social.

Under CCF Article 291-Bis, concubinato is defined as the union of a man and a woman (or, following SCJN interpretive expansion and state-level reforms, of any two persons regardless of sex) who live together as a permanent couple for a period of two or more years without impediments to marry, or who have had children together regardless of the duration of cohabitation. The two-year minimum cohabitation requirement under federal law may be reduced or eliminated in states that have modified their civil codes to require a shorter period or to recognize concubinato from the moment the parties formally register or document their union.

CCF Article 291-Ter establishes the alimentary obligations between concubinos — each concubino has the right to receive alimentos from the other during the union, and upon its termination, the economically vulnerable concubino may claim post-separation support for a period proportional to the duration of the union. This alimentary right is independent of the concubino's capacity to work and is calculated based on the same proportionality standard as spousal support in marriage under CCF Articles 288 through 290.

CCF Article 291-Quater establishes that upon death of a concubino without a will, the surviving concubino inherits in the same proportion as a legal spouse in intestate succession under the applicable provisions of the Código Civil Federal governing sucesión legítima — this right applies only when the concubinato has been legally established for the minimum period and when neither concubino was married to another person during the union. The Ley del Seguro Social Article 84-Bis and Articles 127 through 132 of the Ley del ISSSTE provide IMSS and ISSSTE survivor and beneficiary rights equivalent to those of spouses for registered or documented concubinos, requiring the surviving concubino to demonstrate the union's duration and permanence.

The formal Acuerdo de Unión Libre provides essential documentary evidence of the concubinato for all administrative and legal purposes — IMSS beneficiary registration, INFONAVIT joint housing applications, tax filing as household unit, financial account beneficiary designations, hospital medical decision-making authority, and judicial proceedings to enforce alimentary or inheritance rights.

The Ley General de Salud and hospital regulations in Mexico recognize the concubino's authority to make medical decisions for an incapacitated partner — but only when documentary evidence of the concubinato relationship is presented to hospital staff. A formal Acuerdo de Unión Libre, particularly one executed before a Notario Público, provides the strongest evidence of the relationship for hospital admission forms (formatos de admisión hospitalaria) and for organ donation consent under the Ley General de Salud Article 324. Without such documentation, blood relatives may legally take precedence over the cohabiting partner in medical decision-making, even after decades of life together — a situation that the formal acuerdo is specifically designed to prevent.

The CCF concubinato framework also intersects with Mexico's immigration law for foreign nationals. The Instituto Nacional de Migración (INM) under the Ley de Migración recognizes documented concubinato as a family relationship basis for Tarjeta de Residencia Temporal and Residencia Permanente applications — the INM's family unity procedure requires the Mexican or resident concubino to sponsor the foreign partner's immigration application, presenting the Acuerdo de Unión Libre alongside supporting evidence of cohabitation such as joint bank account statements, lease agreements, utility bills, and photographs. The INM immigration officer evaluates the totality of this documentary record to confirm that the concubinato is genuine, permanent, and meets the two-year threshold under CCF Article 291-Bis, or that the couple has children together qualifying for immediate recognition regardless of duration.

For AFORE retirement savings, a documented concubino who survives their partner may claim survivor pension benefits (pensión por viudez) under the Ley del Seguro Social Articles 127 through 132 — but only upon presenting a judicial declaration of concubinato (declaración judicial de concubinato) to the IMSS and the relevant AFORE institution. The Acuerdo de Unión Libre significantly strengthens the evidentiary foundation for this judicial declaration, reducing the time and cost of obtaining recognition of survivor rights when they are most urgently needed.

A Cohabitation Agreement Mexico is needed whenever two unmarried partners who are living together in Mexico wish to formally document their union libre relationship to activate and protect the legal rights that arise from concubinato under the Código Civil Federal Articles 291-Bis through 291-Quater and applicable state civil codes.

The acuerdo is needed when registering one partner as a beneficiary under the other's IMSS (Instituto Mexicano del Seguro Social) medical coverage. Under Article 84-Bis of the Ley del Seguro Social, concubinos qualify as IMSS beneficiaries (derechohabientes) with the same rights as spouses, but only upon presenting documentary evidence of the concubinato — either a judicial declaration (declaración judicial de concubinato) or documented evidence such as a formal cohabitation agreement, shared lease, and joint utility bills. The IMSS Subdelegación reviewing the beneficiary application will require evidence establishing the duration and permanence of the union.

The document is needed when applying for an INFONAVIT housing credit (crédito INFONAVIT) as a joint applicants — INFONAVIT's co-applicant (coaccreditado) program for couples requires evidence of a stable relationship, and documented concubinato satisfies this requirement. Under the INFONAVIT regulations, co-accredited concubinos can combine their housing subaccount balances and credit capacities to access a larger mortgage amount than either could qualify for individually.

A formal Acuerdo de Unión Libre is needed when one partner wants to designate the other as heir or primary beneficiary in a will (testamento) — while a will itself creates the inheritance right, having a documented concubinato also protects the surviving partner's intestate succession rights under CCF Article 291-Quater if the deceased partner dies without a will. Courts evaluating intestate claims from a concubino require evidence of the union's duration and stability.

The acuerdo is required in family proceedings involving children born to the concubinos — the document establishes that both parents are in a stable family unit, supports joint custody arrangements, and provides context for child support calculations under CCF Articles 301 through 323 that account for the family's household income and expenses.

The agreement is needed for tax planning purposes — partners in a documented concubinato may qualify for certain ISR deductions available to family members under the Ley del Impuesto sobre la Renta, and may make joint decisions about asset ownership, investment structures, and estate planning with a clearer legal framework than undocumented cohabitation provides.

Finally, the acuerdo is needed when one or both partners are foreign nationals — the Instituto Nacional de Migración (INM) recognizes documented concubinato as a basis for family unity immigration applications, allowing a foreign national partner to apply for Tarjeta de Residencia Temporal on the basis of family ties to a Mexican national or a foreign resident. Additionally, the agreement is needed when partners apply jointly for an INFONAVIT co-accredited credit (crédito coaccreditado) for housing purchase — INFONAVIT requires evidence of a stable couple relationship, and a formal Acuerdo de Unión Libre satisfies this requirement. Partners who pool their INFONAVIT housing subaccount balances through the co-accredited program can access significantly larger credits than either could qualify for individually, making formal documentation a direct financial benefit beyond its legal protective functions.

A comprehensive Cohabitation Agreement Mexico under CCF Articles 291-Bis through 291-Quater should address the following elements to document the concubinato effectively and protect both partners' rights under Mexican law.

Identification of Both Concubinos: Full legal name, date of birth, nationality, CURP (Clave Única de Registro de Población), RFC (Registro Federal de Contribuyentes), INE credential or passport number, occupation, and current domicile of each partner. Declaration that neither partner is currently married or in another active concubinato — a fundamental requirement under CCF Article 291-Bis, which requires freedom from matrimonial impediments (impedimentos matrimoniales) for concubinato rights to arise.

Declaration of Cohabitation: Specific statement of the date on which the partners began living together (fecha de inicio de la convivencia), the address of the shared home, and a declaration that the union is permanent, stable, and exclusive. Reference to corroborating evidence of cohabitation — joint lease or property deed, joint utility accounts, shared bank accounts, or children's birth certificates naming both partners as parents — strengthens the document's evidentiary weight.

Property Arrangements: Specification of how property acquired before and during the cohabitation is owned — individually in each partner's name, jointly (copropiedad), or under an agreed arrangement. Unlike marriage, concubinato does not automatically create a community property regime under federal law (though some state codes have introduced limited community property rights for long-term concubinato). The agreement should specify: which assets each partner owns individually; any jointly held assets and the ownership percentage; how jointly acquired assets will be divided upon termination of the union; and which partner administers shared household expenses.

Household Expense Contribution: Agreed division of shared household expenses (gastos del hogar) — rent or mortgage, utilities, food, children's expenses. Under CCF Article 291-Ter, both concubinos are obligated to contribute to household support proportionally to their respective economic capacities, mirroring the marital obligation under CCF Article 164.

Alimentary Rights and Obligations: Explicit acknowledgment of each partner's right to alimentos from the other during the union and post-separation, under CCF Article 291-Ter. If one partner has significantly lower income or is not employed outside the home — for example due to childcare responsibilities — the agreement should address post-separation support duration, amount, and indexation to the INPC published by the INEGI.

Children and Parental Responsibilities: If the concubinos have minor children or anticipate having children, the agreement should address physical custody default arrangements, joint exercise of patria potestad under CCF Article 416, child support contributions, and the process for custody and support arrangements upon separation. Reference to LGDNNA Article 26 and the interés superior del menor standard.

IMSS and INFONAVIT Beneficiary Designation: Declaration of intent to register the other partner as an IMSS beneficiary under Ley del Seguro Social Article 84-Bis and as an INFONAVIT co-applicant where applicable. Acknowledgment that each partner will cooperate in providing required documentation for beneficiary registrations.

Inheritance and Estate Planning: Reference to CCF Article 291-Quater intestate inheritance rights, and the partners' stated intention regarding testamentary planning — particularly the mutual designation as primary heir in each partner's testament (testamento notarial). Forms-legal.com provides this Cohabitation Agreement Mexico template as a practical framework — legal advice from a licensed abogado is recommended for complex asset arrangements, and notarization significantly strengthens the document's evidentiary value in subsequent administrative and judicial proceedings.

Dispute Resolution and Governing Law: A clause specifying that any dispute arising from the concubinato relationship — including claims for alimentos post-separation, division of jointly held property, or inheritance rights — will be submitted first to mediation before the Centro de Justicia Alternativa of the competent Tribunal Superior de Justicia, and then, if unresolved, to the Juzgado de lo Familiar of the jurisdiction where the shared home is located. The governing law is the Código Civil Federal and the applicable state civil code of the state where the partners are domiciled. For couples domiciled in Ciudad de México, the CCDF and the Ley de Sociedad de Convivencia para el Distrito Federal supplement the CCF framework.

Children Born During the Concubinato: Where children are born during the concubinato, both parents must ensure their formal legal recognition — the father's recognition (reconocimiento voluntario de paternidad) before the Registro Civil under CCF Articles 369 through 373, or through simultaneous registration of both parents on the Acta de Nacimiento at birth. Children recognized by both parents within the concubinato have exactly the same legal rights as children born within marriage under CCF Article 338, including rights to alimentos from both parents, intestate inheritance from both parents' estates, and IMSS beneficiary registration under both parents' IMSS registrations. The Acuerdo de Unión Libre can designate the process to be followed for recognizing future children and for establishing paternity without contested judicial proceedings.