# Addendum

Source: https://contracko.com/glossary/addendum

# Addendum

A supplementary document that adds to or amends an existing contract without replacing it.

## Definition

An addendum is a separate instrument signed by the parties that modifies, clarifies or extends terms of an existing contract while leaving the rest intact. It is the standard way to change agreed terms during the contract term, for instance to adjust pricing, scope or duration. To be effective it should reference the original contract and be signed by authorised signatories of both parties.

## Example

> Mid-term, the parties sign an addendum raising the annual fee by 4% and extending the term by one year, leaving all other clauses unchanged.

## Why this is a business risk

An addendum that is poorly drafted or not signed by authorised signatories may fail to legally amend the underlying contract, meaning the original terms continue to apply. If addenda accumulate without a clear version history, it becomes difficult to know which version of a clause is currently in force. Relying on informal email exchanges rather than a signed addendum leaves agreed changes legally precarious.

## How to manage it

- Every amendment should be captured in a signed addendum that references the original contract by name and date.
- Clearly state which clauses are replaced, added or deleted, and reproduce the new wording in full to avoid ambiguity.
- Number addenda sequentially so the version history is transparent and the latest state of each clause can be reconstructed.
- Store each addendum alongside the original contract in your repository so both are always retrieved together.

### How Contracko helps

Contracko links addenda to their parent contract in the repository, so you always see the full document set in one place. Version control tracks when each addendum was added and the AI extraction re-analyses the updated obligation set, flagging if a new fee, extended term or changed notice period needs a corresponding reminder update.

## Relevant for

[IT Services](https://contracko.com/industries/it-services)[Commercial Real Estate](https://contracko.com/industries/commercial-real-estate)[Consulting](https://contracko.com/industries/consulting)

## Related clauses

- [Change Order (Variations) Clause](https://contracko.com/clause-library/change-order)
- [Entire Agreement Clause](https://contracko.com/clause-library/entire-agreement)

## Related terms

- [Order of precedence](https://contracko.com/glossary/order-of-precedence)
- [Retroactive effect](https://contracko.com/glossary/retroactive-effect)
- [Effective date](https://contracko.com/glossary/effective-date)
- [General terms and conditions](https://contracko.com/glossary/general-terms-and-conditions)

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## Frequently asked questions

Common questions about this term.

- **Q:** What is the difference between an addendum and an amendment?
  **A:** In common usage the terms are interchangeable. Some practitioners use "addendum" for additions and "amendment" for changes, but legally both are modifications to an existing contract and the same rules apply.

- **Q:** Does an addendum need to be witnessed or notarised?
  **A:** Only if the underlying contract required those formalities. Most commercial contracts do not, so a signed addendum by the authorised parties is sufficient.

- **Q:** Can one party unilaterally issue an addendum?
  **A:** No. An addendum is a bilateral agreement and requires the consent and signature of all contracting parties to be effective.

- **Q:** What happens if an addendum conflicts with the original contract?
  **A:** The addendum typically prevails as the later expression of the parties' intent, especially if it explicitly states it supersedes the conflicting provision. An order-of-precedence clause can confirm this ranking.

- **Q:** Is an email confirmation sufficient to amend a contract?
  **A:** It may create a binding obligation depending on the circumstances, but it is legally precarious compared to a signed addendum. If the contract contains a "no oral modification" or "entire agreement" clause, informal email changes are likely ineffective.

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