Amendment vs Addendum

The short answer

An amendment edits what is already in the contract. An addendum adds something new next to it. In practice the labels are not always used strictly, so read what the document does, not what it is called.

With SaaS vendors, there is a third path: the vendor changes its online terms by posting a new version, with no signed document at all.

Amendment

• What it is: a document that changes, removes or replaces specific terms in an existing agreement. For example, it may raise a fee, extend the term or rewrite the liability clause.
• Who it binds: the parties to the original contract. A contract may say changes need a written amendment signed by both sides.
• Typical content: a reference to the original agreement, the exact sections being changed, the new wording, an effective date, and a line saying everything else stays the same.

Addendum

• What it is: a document that adds terms on a subject the main contract does not cover in detail. Common SaaS examples are a data processing addendum (DPA), a security addendum, a business associate agreement and AI terms.
• Who it binds: the same parties. It becomes part of the agreement, often by being signed or by being referenced in it.
• Typical content: its own definitions, obligations and sometimes a rule on which document wins if they conflict.

The Atlassian Customer Agreement shows how this can work. Its section 20.6 says the main body controls, but its policies, product terms and DPA "will control for their specific subject matter."

Which one applies to you

Use these steps when a vendor sends you a new document or announces a change. They help you see what changed and whether you agreed to it.

1. Identify what the document does. If it rewrites an existing clause, treat it as an amendment, whatever its title.
2. Check whether it needs your signature. If the contract requires signed amendments, a vendor email alone may not change it.
3. Check the order of precedence. An addendum may say it overrides the main agreement on its topic.
4. Check whether the addendum lives online. A posted addendum, such as a DPA on the vendor's website, may be updated without a new signature.
5. Look for a unilateral amendment clause. This lets the vendor change terms by posting them, often with notice. Atlassian's agreement (section 20.9) lets it modify the agreement by posting changes online, with a goal of posting at least 30 days before they take effect.

Whether a change made this way binds you depends on your contract and on state law, so the notice wording matters. See notice of changes to terms.

Keep a simple record for each vendor: the signed agreement, every signed amendment, every addendum, and a dated copy of each online document the contract refers to. When a dispute comes up, you will need to show which version applied on which date, and the vendor's current website will only show the latest one.

Example

Venpo flagged a change where Hotjar's DPA can now change without your signature. A DPA is an addendum. The old version said changes needed both sides' written agreement. The June 2026 version, now published by Contentsquare, which runs Hotjar, says it may change the DPA at any time in its sole discretion, much like online terms.

For example, imagine you signed an MSA that requires written amendments. Later, the vendor posts a new AI addendum and says it applies to everyone using AI features. You would check whether your MSA lets online addenda in, and whether turning on the AI feature counts as accepting it.

How Venpo helps

Many vendor changes arrive as online updates rather than signed amendments. Venpo monitors your vendors' terms, DPAs, AI terms and other public legal pages, and emails a plain-English alert when one changes, with a change history per vendor.