Addendum
An addendum is a separate document attached to a contract that adds terms, details or conditions the main contract doesn't cover.
Updated November 5, 2026 · 1 min read
Addendum vs amendment
An addendum usually adds something, often at signing: a pet addendum to a lease, a lead paint disclosure, or a schedule of materials. An amendment changes terms the parties already agreed. People mix the words up, so the document should say what it does: which contract it belongs to, what it adds, and the date.
What to include
- The title and date of the contract it attaches to, and the parties' names.
- The added terms, numbered so they can be referred to.
- A line saying the original contract stays in force except as the addendum adds.
- Signatures from everyone who signed the original.
In SignMaster
Send the contract and its addendum in one envelope: an envelope can hold more than one document, and signers sign both in one sitting. For an addendum added later, send it as its own envelope to the same people. There's a pet addendum template in the library to start from.
Questions? Answers.
Does an addendum need to be signed?
Yes. Have every party to the original contract sign it, so it's clear they all agreed to the added terms.