A lease addendum is a short document that changes or adds to a lease that’s already signed, without rewriting the whole thing. Landlords and tenants use one when something comes up mid-lease: a new dog, a second parking spot, a rent change, a partner moving in. Our free lease addendum template in Word and PDF has optional sections for those four, plus a blank section for anything else.

When do you need a lease addendum?

You need one whenever both sides agree to change something in the lease while it’s still running. A verbal “sure, the cat’s fine” is easy to forget and hard to prove a year later, when the deposit is being split up.

Here’s a hypothetical. Dana rents a two-bedroom from a small landlord on a 12-month lease that says no pets. In month five she wants to adopt a beagle. The landlord agrees, with a $300 pet deposit and $35 a month in pet rent. Ten minutes with a residential lease addendum covers it: which dog, the deposit, the monthly charge, who pays for damage. Everyone signs, and it’s part of the lease from then on.

An addendum isn’t always the best tool, though:

  • If the lease is ending and you’re agreeing to a new term, use a lease renewal agreement. You can list changed terms in the renewal instead of stacking an addendum on top.
  • If the changes are so big that half the lease would be crossed out, sign a fresh residential lease agreement.
  • If you’re switching from a fixed term to a rolling arrangement, a month-to-month rental agreement is clearer than an addendum.

How does an addendum relate to the original lease?

An addendum becomes part of the original lease once everyone signs it, and it only changes what it says it changes. Everything else in the lease, including the end date, the deposit terms and the rules on repairs, keeps going exactly as before.

That’s why our template opens by identifying the lease (its date, the property and the parties) and says that if the addendum and the lease disagree, the addendum wins for the terms it covers. Most leases, including ours, say changes must be in writing and signed by both sides. An addendum is how you meet that rule.

People sometimes ask whether an addendum and an amendment are different. In everyday use they overlap a lot. Some people say “addendum” for something added (a pet) and “amendment” for something changed (the rent). The label matters less than what’s written and who signed it.

What should a lease addendum include?

Our lease addendum form is built so you fill in the reference block and then tick only the sections you need. Unused sections get marked “not used,” so nobody wonders later whether something was deleted.

Reference to the lease. The date of the original lease, the property address and unit, every landlord and tenant by full legal name, and the date the addendum takes effect.

Pet (optional). The animal’s type, breed, name and approximate weight, any pet deposit or monthly pet rent, the tenant’s responsibility for damage and waste, and any rules on leashes or noise. One thing a pet section shouldn’t touch: assistance animals. HUD’s guidance says an assistance animal is not a pet, that housing providers may not require a deposit for one, and that pet rules can’t simply be applied to it. A tenant can still be charged for damage the animal actually causes, as long as other tenants are charged for damage too. If a tenant asks to keep an assistance animal, treat it as an accommodation request, not a pet addendum. Our template says so in that section.

Parking (optional). The space number or location, the vehicle, any monthly fee, and what happens with towing or guest parking.

Rent change (optional). The old rent, the new rent, the date it starts, and whether anything else (due date, late fee) changes. State and local rules can limit rent increases and set notice periods. California’s Attorney General, for example, tells tenants that a landlord must give formal written notice at least 30 days before an increase takes effect, or at least 90 days if it’s more than 10%, and that a call, text or email isn’t enough. Signing an addendum where the tenant agrees to the new rent is a different thing from a one-sided notice, but if your area has rent control or a cap, the addendum can’t override it.

Added occupant (optional). The new person’s name, whether they’re becoming a tenant (equally responsible for rent and the lease) or just an approved occupant, and whether the rent or deposit changes. If they’ll be a tenant, they sign the addendum.

Other changes. A blank section for anything else: a new end date for a short extension, permission to paint, a storage unit, a satellite dish.

Who has to sign a lease addendum?

Every person who signed the lease should sign the addendum, and a new co-tenant should sign as well. If two roommates are on the lease and only one signs a rent increase, you’ve got an argument waiting about whether the other one ever agreed to it.

Signing order doesn’t change the legal effect, but we suggest the same order as our lease: tenants sign first, then the landlord countersigns. That way the landlord signs only once every tenant is on board, and the fully signed copy goes out to everyone in one step.

What should you check for your state?

Check three things before you use a lease addendum template. First, rent increase rules: caps, rent stabilization and notice periods vary a lot by state and city. Second, fees: some places limit total deposits (and a pet deposit counts), or limit fees in general. Third, the lease itself. If your lease came from a state realtor association or a property manager’s standard form, it may have its own addendum forms, and using those keeps everything consistent. Your state attorney general or court self-help site is usually the quickest place to look.

How do you fill it in and get it signed?

  1. Fill in the reference block so the addendum points to exactly one lease.
  2. Tick the sections you need and fill them in. Mark the rest “not used.”
  3. Check any amounts against your local rules on rent, deposits and fees.
  4. Send it to every tenant for signature, then the landlord countersigns.
  5. Give everyone a signed copy and keep it with the original lease.

E-signing an addendum is generally fine. The federal ESIGN Act says a contract can’t be denied legal effect solely because an electronic signature was used to form it. Our guide on whether electronic signatures are legally binding covers the details, including the few notices about a primary residence that have their own rules.

Download it, fill in the blanks, and send it for e-signature with any tool you like. (SignWren does exactly this; you can start free.)

This template and guide are general information, not legal advice. For a specific lease or dispute, talk to a lawyer licensed where the property is.