A contract addendum adds something to an agreement without changing what is already there. A new service under the existing terms, an extra site, an additional schedule of prices for work the original did not cover. It is the quieter sibling of the amendment and it causes more record problems, because adding rarely feels like changing and so it is filed with even less ceremony. This page covers what an addendum does, when to use one instead of an amendment, and what has to be recorded.
What an addendum does, and the test against an amendment
The test is simple. If the original agreement would still be accurate after the change, you are adding, and an addendum is right. If some sentence in the original would become wrong, you are altering, and it is an amendment. A new schedule of services under the same terms is an addendum. Changing the payment period from thirty to sixty days is an amendment, because the original clause would now be wrong.
What belongs in one
Identification of the original agreement by name and date. What is being added, in full rather than by reference to a conversation. Whether the addition takes effect immediately or on a date. Confirmation that the original terms govern the added material, which is the sentence people forget and the one that decides which liability cap and which notice period apply to the new part.
What to record, which is more than people expect
The addition itself, and then anything downstream of it. If the addendum adds a service, the annual value changes. If it adds a site or a deliverable, there are probably new obligations with owners. If it has its own end date, you now have two dates on one agreement and the record has to hold both. Attach the addendum with a one-line description of what it added.
The question an addendum usually leaves open
Whether the added material ends when the original agreement ends. Often the original governs and it does; sometimes the addendum has its own term and it does not. If the addendum does not say, note the ambiguity on the record and use the earlier date for any notice you rely on, because assuming the longer one is how a business finds itself still paying for the added service after the main agreement stopped.
Questions people ask about contract addendum
What is a contract addendum?
A document that adds something to an existing agreement without altering what is already there, governed by the original terms unless it says otherwise.
What is the difference between an addendum and an amendment?
If the original would still be accurate afterwards, it is an addendum. If a sentence in the original would become wrong, it is an amendment.
Does an addendum have its own end date?
Sometimes. If it does not say, the original usually governs, but the ambiguity is worth noting on the record and resolving with the other side rather than assuming.
Do addenda need to be signed?
Yes, by the same parties with the same authority. An addendum is as binding as the agreement it attaches to.