Lease Addendum Mexico (Addendum al Contrato de Arrendamiento)

A Lease Addendum Mexico (Addendum al Contrato de Arrendamiento) is a written supplementary agreement that amends, extends, or adds new terms to an existing lease contract (contrato de arrendamiento) between a landlord (arrendador) and a tenant (arrendatario), without replacing the primary lease agreement in its entirety. The addendum is governed by Código Civil Federal (CCF) Article 2478, which establishes that lease modifications must be made by mutual written agreement of both parties, and by the general principles of contract novation (novación) and modification established in CCF Articles 2213 through 2218. The addendum is incorporated by reference into the original lease and forms an completo part of the overall lease relationship.

CCF Article 2478 establishes the baseline rule for lease terms: where no fixed term is agreed, the lease is presumed open-ended and terminable on notice equal to the rent period. Where the parties have agreed a fixed term (plazo forzoso) and wish to extend it, CCF Article 2478 governs the legal basis for the extension — a formal written addendum signed by both parties extending the plazo forzoso prevents the ambiguity of tácita reconducción (tacit renewal as an open-ended lease) that would otherwise arise under CCF Article 2478 if the tenant continues to occupy the property after the fixed term expires without a new agreement.

A Lease Addendum in Mexico may serve several distinct purposes: extension of the lease term (prórroga del plazo); adjustment of the monthly rent (modificación de la renta) — either a negotiated adjustment outside the original rent increase mechanism, or an agreed adjustment to the index linkage (vinculación al INPC); addition of new clauses covering matters not addressed in the original lease (e.g., a pet permission clause, a home office use clause, an authorisation for subletting under CCF Article 2480, or a parking assignment modification); correction of errors in the original lease (corrección de datos); or modification of the security deposit amount (modificación del depósito en garantía).

For tax reporting purposes under Ley del Impuesto sobre la Renta (LISR) Article 114, a lease addendum that changes the monthly rent requires the arrendador to update their monthly provisional ISR payment calculations with the Servicio de Administración Tributaria (SAT) to reflect the new renta amount. The arrendador must continue issuing Comprobantes Fiscales Digitales por Internet (CFDI) for each rent payment at the revised amount and update the invoice description to reference the addendum date and the modified rent amount. The addendum itself does not require notarisation for leases of less than six years under CCF Article 2406, but notarisation provides evidentiary advantages in disputes before the Juzgado Civil competente.

In the commercial lease context — leases governed additionally by the Código de Comercio (CCom) — lease addenda modifying rent, extending terms, or changing permitted use are particularly common and must be carefully drafted to ensure they do not inadvertently create a novación (novation) that extinguishes the original lease and the guarantees (fianzas) or security deposits provided by the tenant under the original agreement. Under CCF Articles 2213 and 2214, novación — the substitution of a new obligation for an existing one — extinguishes the original obligation and all accessory securities unless the parties expressly agree that the securities survive the modification. A well-drafted addendum should expressly state that it does not constitute a novación and that all guarantees, fianzas, and security deposits under the original lease remain in full force.

Mexican commercial landlords and tenants frequently use addenda to implement agreed rent concessions (condonaciones temporales de renta) during economic downturns, business interruptions, or extraordinary events such as the COVID-19 pandemic. PROFECO (Procuraduría Federal del Consumidor) has issued guidance recommending that commercial parties document any rent concessions in writing to prevent subsequent disputes about whether reduced payment constituted a waiver or a contractual modification.

A Lease Addendum Mexico is required whenever the landlord (arrendador) and tenant (arrendatario) mutually agree to change any term of an existing lease agreement — whether residential or commercial — without terminating and replacing the entire lease contract. The addendum preserves the continuity of the lease relationship, maintaining the security deposit, fianza, and all accessory obligations, while documenting the agreed changes with the same legal formality as the original lease.

The Addendum al Contrato de Arrendamiento is needed when an existing fixed-term lease (plazo forzoso) expires and both parties wish to extend the tenancy without executing an entirely new lease — a term extension addendum prevents the ambiguity of tácita reconducción under CCF Article 2478, under which continued occupancy without a new agreement converts the fixed-term lease to an open-ended arrangement terminable on 30 days' notice.

The addendum is required when the parties negotiate a rent adjustment outside the original rent increase mechanism — for example, a below-INPC increase agreed during an economic downturn, or a rent reduction in exchange for the tenant agreeing to a longer commitment period (plazo forzoso ampliado). The written addendum documenting the new rent amount allows the arrendador to update their CFDI issuance and SAT provisional ISR payment calculations under LISR Article 114.

A lease addendum is also required when the landlord wishes to add a clause that was not in the original lease — for example, an authorisation for the tenant to sublet under CCF Article 2480 (which requires express written landlord consent); permission for a home-based business (negocio en casa) that modifies the original uso habitacional restriction under CCF Article 2416; or addition of a fiador (personal guarantor) when the original lease did not include one.

Under CCF Article 2478 and the general principles of contract modification established in CCF Articles 2213 through 2218, both arrendador and arrendatario benefit from a written addendum that clearly identifies the original lease being modified, states the effective date of each modification, expressly confirms that all non-modified terms of the original lease remain in full force, and declares that the addendum does not constitute a novación — protecting all accessory securities and fianzas from inadvertent extinguishment.

A valid Lease Addendum Mexico under CCF Article 2478 and applicable state civil codes must contain the following essential elements to be enforceable and to properly integrate with the existing lease agreement.

Identification of Original Lease: Precise identification of the lease agreement being modified — the date of the original lease, the names of the arrendador and arrendatario as stated in the original lease, the property address, and the lease reference number or folio if applicable. This cross-reference ties the addendum to the primary agreement and confirms which lease is being amended.

Identification of Parties: Confirmation of the current arrendador and arrendatario — with their RFC, official identity document numbers (INE, pasaporte, or Tarjeta de Residencia), and current domicilios. If there has been any assignment (cesión) of the landlord's or tenant's interest since the original lease was executed, the addendum should document the current party's authority to enter into the modification.

Effective Date of Modification: The specific date from which each modification takes effect. Some modifications — such as a rent increase — may take effect at the start of the next payment period; others — such as a term extension — may take effect from the original lease expiration date. Multiple modifications with different effective dates may be included in a single addendum if clearly labelled.

Description of Modifications: Each modification stated separately and precisely. Common modifications include: (a) Term Extension (Prórroga del Plazo) — new lease end date (nueva fecha de vencimiento), confirming that the plazo forzoso extends to the new date and that CCF Article 2478 tácita reconducción is excluded; (b) Rent Modification (Modificación de Renta) — new monthly rent amount in MXN, effective date, and updated INPC or fixed-percentage adjustment mechanism; (c) Permitted Use Modification — addition of specific activities allowed under the amended lease while maintaining uso habitacional or agreed commercial use classification; (d) Subletting Authorisation — express written consent required under CCF Article 2480, identifying the authorised subtenant's name, RFC, and sublease term; (e) Security Deposit Adjustment — new deposit amount and the balance due or to be returned.

Non-Novation Clause (Cláusula de No Novación): An express statement that the addendum does not constitute a novación under CCF Articles 2213 and 2214 — the original lease remains in full force except as specifically modified, and all accessory obligations, fianzas, security deposits, and guarantees provided by the tenant or fiador under the original lease continue in full effect without modification. This clause is essential when the tenant has provided a fianza solidaria — without the non-novation clause, modifying the rent or extending the term might extinguish the fiador's obligation under CCF Article 2218.

Confirmation of Surviving Terms: Express statement that all terms and conditions of the original lease agreement that are not specifically modified by the addendum remain in full force and effect. Reference to specific surviving clauses of the original lease (e.g., maintenance obligations, permitted use restrictions, termination rights) reinforces the continuity of the lease relationship.

SAT and CFDI Implications: For rent modifications, a note that the arrendador will issue updated CFDIs reflecting the new rent amount, and will update monthly provisional ISR payment calculations with the SAT as required under LISR Article 114. No separate registration of the addendum with the SAT is required, but the arrendador's provisional ISR payments must reflect the actual rent received.

Witnesses and Signatures: Signatures of both arrendador and arrendatario, dated and signed in the same city (ciudad de firma) stated in the original lease. While CCF Article 2406 does not require notarisation for lease modifications of less than six years, having two witnesses sign alongside the parties or obtaining a notarial acknowledgment strengthens the addendum's evidentiary value before the Juzgado Civil competente.

Forms-legal.com provides this Lease Addendum Mexico template as a practical starting point. Mexican lease modification law — particularly regarding novation risks, fiador obligation survival, commercial lease modifications under the Código de Comercio, and SAT reporting of rent changes — varies by state and lease type. Every landlord and tenant should consult a licensed Licenciado en Derecho and a contador público autorizado (CPA) familiar with the applicable state civil code before executing any lease addendum in Mexico.