Lease addendum template and how to get it signed
Short answer: A lease addendum adds new terms to an existing lease without rewriting it, a pet policy, a rent change, an added occupant, while an amendment typically changes or replaces specific existing terms within the lease itself. Both need to reference the original lease by date and both parties' signatures to be enforceable, the addendum doesn't take effect just because it's written down, the tenant needs to actually agree to it the same way they agreed to the original lease.
You need to add something to an existing lease, a pet, a new occupant, a rent change, without tearing up and rewriting the whole document, and you want it done properly so it's actually enforceable.
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A lease addendum is one of the most useful small documents in property management precisely because it avoids the alternative, rewriting an entire lease every time something minor changes. Done right, it's a short, focused document that adds exactly one thing to an existing agreement, signed by the same parties who signed the original.
Addendum vs amendment
An addendum adds a new term that wasn't in the original lease, allowing a pet that wasn't previously permitted, adding an occupant, introducing a new house rule. An amendment changes or replaces a term that was already in the lease, changing the rent amount stated in the original document, changing the lease end date. The practical difference matters less than getting the basic structure right either way: reference the original lease by date and parties, state clearly what's being added or changed, and get it signed by everyone who signed the original. Some landlords use "addendum" loosely to cover both, which is fine as long as the document itself is specific about exactly what's changing.
Why not just rewrite the lease instead?
Rewriting the full lease every time something small changes means re-signing a long document for a one-line change, which is slower for everyone and makes it harder to tell, months later, what actually changed and when. An addendum, kept as its own short, dated document referencing the original lease, gives you a clean paper trail: the original lease shows what was agreed at move-in, and each addendum shows exactly what changed and when, without burying that history inside successive full rewrites of the same multi-page document. Saving the form once as a template, as in reusing a lease addendum for every new tenant, removes most of the repeat work.
Common addenda
- Pet addendum. States which specific pet is approved (species, breed if relevant, weight), any pet deposit or monthly pet rent, and any related rules (cleanup, noise, liability for damage). Confirm your state's rules on pet deposits specifically, some states cap or regulate how pet deposits can be structured relative to a standard security deposit, and a few states and cities restrict pet deposits or fees altogether for certain categories like service or assistance animals, which are a separate legal category from an ordinary pet and generally can't be charged a pet deposit or denied under a no-pets policy.
- Added occupant addendum. Names a new adult occupant and typically states they're bound by the same lease terms as the original tenant, important for enforceability if that occupant later causes a lease violation or needs to be addressed directly.
- Rent change addendum. States the new rent amount and effective date, used for a mid-lease rent adjustment agreed to by both parties (distinct from a renewal rent increase, which is usually handled through a new lease or a separate notice depending on your state's rules). For a building-wide change, see how to get every tenant to sign a rent increase or rule change notice.
- House rules or policy addendum. Parking, noise, common area use, or other rules introduced after the original lease was signed, which need the tenant's actual agreement to be enforceable against them, not just a notice posted in a common area.
A filled-in example
"Addendum to Lease dated March 1, 2026, between Sunrise Properties LLC and Jordan Avery for the premises at 118 Maple Court, Unit 2. Effective December 1, 2026, the following is added to the lease: Tenant is approved to keep one domestic cat (indoor only) at the premises, subject to a $250 pet deposit due before the pet's move-in date and a $25 monthly pet rent added to the existing rent amount. All other terms of the original lease remain unchanged and in full effect." Notice it references the original lease precisely by date and parties, states exactly what's changing, and explicitly confirms everything else stays the same, which avoids any ambiguity about whether other lease terms were also affected.
Sending to many tenants at once
If you're rolling out the same addendum across multiple units, a new building-wide policy, a standard pet addendum offered to all current tenants, QuickSigner, an electronic signature tool for sending documents out to be signed online from any device, supports bulk sending on its Professional plan ($15 a month per user, $144 annually), letting you send the same addendum template to many tenants at once rather than handling each one manually. Confirm current pricing and bulk-send limits directly before committing, since plan features and limits can change. For a single addendum with one or two tenants, the Business plan ($5 a month per user, $48 annually) with reusable templates is enough. Electronically signed addenda are enforceable the same way as paper under the US ESIGN Act and state UETA laws, with the same consumer consent disclosure requirement that applies to the original lease itself, since the tenant is still a consumer for this document too, see my lease e-sign workflow guide for how that consent step actually works.
A second worked example: adding an occupant
Say Jordan from the pet addendum example above gets married eight months into the lease and wants to add a spouse, Casey, as a co-occupant. The added-occupant addendum would read: "Addendum to Lease dated March 1, 2026, between Sunrise Properties LLC and Jordan Avery for the premises at 118 Maple Court, Unit 2. Effective November 15, 2026, Casey Morgan is added as an occupant of the premises and is bound by all terms of the original lease, including but not limited to rules regarding conduct, maintenance, and grounds for termination. Casey Morgan is jointly and severally liable for rent and all other obligations under the lease alongside Jordan Avery. All other terms of the original lease remain unchanged and in full effect." The phrase "jointly and severally liable" is doing real work here, it means you can pursue either tenant individually for the full rent amount if payment stops, rather than being limited to collecting half from each. Without that specific language, a landlord can end up in a dispute over whether a newly added occupant is actually on the hook for unpaid rent or just living there with the original tenant's permission, two very different legal positions that look identical day to day until something goes wrong.
A common mistake small businesses make with this document
The mistake I see most often among smaller landlords is approving a pet, an occupant, or a rent change verbally or over text, then never following up with the actual signed addendum because the immediate request has been resolved and it feels like paperwork for its own sake. Six months later, that same tenant's cat damages the flooring, or the added occupant causes a disturbance, and the landlord has no signed document establishing the pet was ever formally approved, what rules applied to it, or that the new occupant agreed to be bound by the lease at all. The text thread where you said "sure, that's fine" doesn't carry nearly the same weight as a dated addendum both sides actually signed. Treat the verbal or text approval as the first step, not the last, and get the signed addendum out within a day or two while it's still fresh and easy for the tenant to complete.
How I'd approach this
I'd keep a small library of the addenda you use repeatedly, pet, added occupant, rent change, as clean, reusable templates rather than drafting a new one from scratch each time, which both saves time and reduces the risk of inconsistent wording across your tenant base. One thing I'd flag specifically: an addendum signed by only one tenant in a multi-tenant lease doesn't bind the others, if a pet or an occupant addendum affects the whole household, get every adult tenant's signature on it, the same way the original lease needed everyone's signature to be fully enforceable. If one tenant is unreachable or unwilling to sign a needed addendum, treat that as a real issue to resolve directly rather than proceeding as if a majority or a verbal okay from the others is good enough, since it generally isn't for something that binds the whole household. For a building-wide policy rollout specifically, I'd also give tenants a reasonable window to ask questions before expecting a signature, a new rule introduced and expected to be signed the same week it's announced tends to generate more pushback than the same rule introduced with two weeks' notice and a chance to raise concerns first. The best e-signature tools for property managers and landlords handle templates and bulk sending.
Questions people ask
Does a lease addendum need to be signed by every original tenant?
Yes, if the lease has multiple tenants, an addendum affecting the lease generally needs all original signers to agree, not just one. A single tenant can't unilaterally bind co-tenants to a new term.
Can a landlord add an addendum without the tenant's agreement?
Generally no for most substantive changes, most new terms added mid-lease require the tenant's actual agreement to be enforceable against them, similar to how the original lease required their signature. A unilateral notice of a new rule isn't the same as an enforceable addendum.
How is a pet deposit typically structured in an addendum?
This varies by state and sometimes by city, some cap total deposits (security plus pet) at a set multiple of rent, others regulate pet deposits specifically as separate from security deposits. Confirm your specific state and local rules before setting the amount.
Does adding an occupant via addendum change who's responsible for rent?
It depends on how the addendum is worded, some simply acknowledge the new occupant without changing payment responsibility, others make the new occupant jointly liable for rent. State this explicitly rather than leaving it ambiguous.
Can an addendum be used to raise rent mid-lease?
Only if both parties agree to it, a standard fixed-term lease generally can't have rent increased unilaterally mid-term regardless of addendum. A rent change addendum documents a mutually agreed change, not a landlord-imposed one during an active lease term.
What happens if I never got a verbal pet or occupant agreement in writing?
Get it documented retroactively as soon as you notice the gap, a signed addendum now is better than continuing with an undocumented informal arrangement. An unwritten agreement is much harder to enforce or point to if a dispute comes up later.