How to Write a Contract Addendum
A contract addendum is a document that is added to an existing contract to modify the terms
of the agreement. If properly executed, it leaves the original contract in full force and effect
and only modifies the specific terms described in the addendum. Note that any change to an
existing contract which is not incorporated through a separate document is an amendment and not an addendum.
Writing Your Contract Addendum
Use a style that is consistent with the original contract
The addendum needs to look like the original contract so that it is clear the two documents
are connected. Use the same typeface, margins and font size. Reference the date of the original contract.
Title the document in a way that shows it is an addendum to the original contract. For example:
"Addendum to January 2, 2009 Employment Contract".
Specify the parties to the contract
For example: This contract is between John Doe ("Employer") and Jane Smith ("Employee").
Include the date upon which the addendum is to become effective.
For example: "This addendum shall become effective as of today, May 5, 2010."
Place the date in a way that is consistent with the original contract. If the original contract included
the date at the beginning of the text, then follow the same format in the addendum.
List the terms and parts of the original contract that the addendum is modifying
Be clear, thorough and concise in describing the modifications. Specify whether each item
replaces a current item in the contract, changes one, or is a new item.
For example: "Item I of the Employment Contract shall be modified as follows with the text
in bold added to the Item and the text containing a strikethrough deleted:"
Use strikethrough and italic or bold font to clarify additions, deletions, and modifications.
Attach the original contract to the addendum and reference the fact that you have done so in
your addendum. For example:
"the original Employment Contract dated January 2, 2009 is attached and made a part of this
document". This will ensure that any party executing the addendum is clear as to which specific
contract the addendum modifies.
Add a signature block
The signature block should contain a blank space for the date the addendum will be executed,
lines for each party to sign, and each party's typed or printed name.
Add a notary block
Each of the party’s signatures on a contract may be notarized in order to prove that he or
she did, in fact, sign the contract.
Understanding the Law
Make sure your addendum complies with the existing contract
For your addendum to be enforceable, it must comply with the terms of the existing contract.
Often, a contract will specify the circumstances under which it can be amended. Therefore, it
is imperative that you read the terms of the existing contract before preparing the addendum.
Be particularly wary of contractual terms that: Prohibit addendums to the contract, especially
with regard to altering specific rights or responsibilities. Allow one party to change the terms
of the contract without the consent of the other parties involved. Set forth specific requirements
for changing the existing contract, such as requiring that any amendment be made in writing and signed by all parties.
Review the applicable law
In addition to complying with the terms of the existing contract, your contract addendum
must meet the requirements of the applicable law. The majority of contracts (i.e. employment
agreements, leases, business agreements) are controlled by the common law of the state in
which the agreement was made.
Contracts for the sale of goods are governed by the Uniform Commercial Code (UCC).
Under the common law of most states, a contract addendum is only enforceable if a right or
asset of value (known as "consideration") is exchanged. Under the UCC, consideration is not
required to make an addendum enforceable.
Contracts governed by both the UCC and common law generally require mutual assent, meaning that
all parties must agree to the important elements of the amended contract.