An addendum is a separate document that becomes part of the Purchase and Sales Agreement. It is used when something needs to be added, clarified, or changed after the main contract has already been written. Once everyone signs the addendum, it becomes legally binding just like the rest of the contract. It does not sit “next to” the agreement; it becomes part of it.
Some addenda are included right from the start. For example, homes built before 1978 must have a lead‑based paint addendum. This is required by federal law and is always attached to the original contract package.
Other addenda are created later, usually because something in the transaction needs to be adjusted. Common reasons include extending the closing date, changing a deadline, adding or removing a contingency, addressing home inspection findings, adding seller credits, or updating occupancy terms. Instead of rewriting the entire Purchase and Sales Agreement, the parties sign an addendum that clearly states the change.
An addendum does not replace the original contract. It simply becomes an additional page that modifies or expands the terms everyone already agreed to. In New Hampshire transactions, addenda are extremely common and are the standard way to keep the contract accurate as the deal moves forward.