What is a lease addendum and when should you use one?
A lease addendum is a separate signed page that adds to or changes the terms of a lease, either at signing or partway through. Use one for a topic that needs its own rules, such as pets, parking or a required disclosure, or to change a term mid-lease when both sides agree. It binds only if every party to the lease signs it.
Addendum, amendment or a new lease?
People use "addendum" and "amendment" loosely. A common way to keep them apart: an addendum adds a topic the lease does not cover, often signed with the lease; an amendment changes a term already in it, during the lease. Both must be in writing and signed by the same parties as the lease. If you are changing most of the lease, sign a new lease instead.
| Situation | Use |
|---|---|
| Tenant gets a dog after move-in | Pet addendum |
| Rent changes mid-lease by agreement | Amendment to the rent clause |
| New roommate joins | Addendum adding the occupant, or a new lease if they will be a tenant on it |
| Pre-1978 building at signing | Lead-based paint disclosure attached to the lease |
| Lease renewed with new rent and a new term | New lease or a renewal agreement |
Common addenda for apartments
- Pets: which animals, fees or deposits where your state allows them, cleanup and damage rules. Assistance animals are not pets; see assistance animals and pet policies.
- Parking: assigned space, towing rules, vehicle list.
- Utilities: which bills the tenant pays, how shared water is split.
- Smoke-free building: where smoking is not allowed.
- Renter's insurance: required coverage and proof.
- Storage, bike rooms and amenity rules.
- Mold, bed bug or other state-required notices.
Disclosures the law requires on paper
Some addenda are not optional. For housing built before 1978, federal rules require landlords to disclose known lead-based paint and hazards, give the EPA pamphlet, and provide a Lead Warning Statement that can be attached to the lease or inserted into it, before the renter signs. Keep the signed disclosure for three years (EPA). The details and exemptions are in lead-based paint disclosure for rentals.
States add their own. Florida, for example, requires a set radon gas notice, word for word from the statute, to be provided at or before signing a rental agreement for a building, except for transient stays of 45 days or less (Florida Statutes 404.056(5)). Check your state for others, such as mold or flood notices.
How to write and sign one
- Title it clearly, such as "Pet Addendum to Lease dated March 1, 2026, Unit 3A".
- Name the property, unit, every tenant and the owner exactly as in the lease.
- State the start date and, for an amendment, the exact clause it replaces.
- Add one line: "If this addendum conflicts with the lease, this addendum controls on its subject. All other lease terms stay the same."
- Have every adult tenant and the owner sign and date it. A guarantor should sign too if the change affects what they guarantee.
- Give each signer a copy and file it with the lease.
Example a made-up tenant on a $1,450 lease adopts a cat in month five. The owner's pet policy charges $35 a month pet rent. The addendum, signed by both tenants and the owner, sets rent at $1,485 from June 1 and adds the pet rules. Over the remaining seven months the owner collects $245 in pet rent, and the rent roll shows $1,485 so the payment amount matches.
One caution: an addendum cannot take away rights the law gives the tenant. A clause waiving required entry notice, for example, generally will not hold.
How DoorKeeping handles it
DoorKeeping sends leases for e-signature. When an addendum changes rent, you update the unit's rent in DoorKeeping, approve the change with one tap, and the tenant's exact payment amount and memo stay in step with the new rent. DoorKeeping is $2 per unit per month, and it does not give legal advice.
Sources
- EPA, Real Estate Disclosures about Potential Lead Hazards, read Oct 29, 2026
- Florida Statutes 404.056, radon notification, read Oct 29, 2026
Questions
- Does a lease addendum need to be signed by both parties?
- Yes. Every tenant on the lease and the owner should sign and date it, or it may not bind the person who did not sign.
- Can a landlord add an addendum in the middle of a lease?
- Only by agreement. A landlord generally cannot add new terms mid-lease on their own; the tenant must agree and sign.
- Is a lead paint disclosure an addendum?
- For pre-1978 housing it is usually handled as one: the Lead Warning Statement can be attached to the lease or inserted into it, and must be given before the tenant signs.