Contract Addendum Template (Free Sample)

What is a contract addendum?

An addendum (plural: addenda) is a document attached to a contract that adds to it. It can be signed at the same time as the main contract, to add terms that do not fit the standard form, or later, to add or change terms after the contract is signed. Once the parties sign it, the addendum becomes part of their agreement, and the original contract and the addendum are read together.

An addendum is useful because it lets the parties change one or two points without re-signing the whole contract. It is common with standard-form contracts, such as residential leases and real estate purchase contracts, where the parties keep the printed form and put their own terms in an addendum.

Addendum vs amendment vs rider vs exhibit

These labels are used loosely, and the same document can be called an addendum by one lawyer and an amendment by another. What matters legally is what the document says and that the right parties signed it, not its title. In general US usage:

If the changes are so extensive that the contract becomes hard to follow, an amended and restated agreement (a full new version that replaces the old one) is often clearer than a stack of addenda.

When to use a contract addendum

• To add terms at signing. The parties are using a standard form and need terms it does not cover, such as a pet policy, an early move-in or a special condition of sale.
• To change terms after signing. The price, a deadline, the term, the scope of work or a delivery date changes, and both sides agree to the change.
• To attach a required disclosure. Some disclosures are commonly attached to a contract as an addendum, such as the federal lead-based paint disclosure for most housing built before 1978.
• To clarify a term. The parties agree on what an unclear clause means and want that recorded.

An addendum is not always the right tool. To transfer a party's rights or performance duties, you may need an assignment and delegation, with any consent required by the contract or applicable law. That generally does not release the original party from its obligations. Substituting a new party and releasing the original party usually requires a novation agreed to by all affected parties, or another legally effective release. If the contract has expired, an addendum to it may not revive it; a new agreement is safer. And if the changes touch most of the contract, use an amended and restated agreement.

What to include in a contract addendum: checklist

• A title that names the original contract. For example, "Addendum No. 1 to the Services Agreement dated March 3, 2026". Number addenda if there may be more than one.
• The parties. The same legal names as in the original contract. If a party's name has changed, say so.
• The original contract. Its title, date and any earlier addenda or amendments, so there is no doubt which document is being changed.
• The changes, section by section. Say exactly what is added, deleted or replaced, using the original section numbers, and quote the new wording in full. Avoid vague wording such as "the parties agree to adjust the price".
• The effective date. When the change takes effect, which may differ from the date the addendum is signed.
• Consideration, where needed. What each side gives in exchange for the change (see the next section).
• A conflict clause. That the addendum controls if it conflicts with the original contract on the points it covers.
• A "rest unchanged" clause. That everything not changed by the addendum stays in effect.
• Signatures. Signature blocks for every party to the original contract, signed by people with authority to bind them, with the date of each signature.
• Anything the original contract requires. Check its amendment clause: many contracts say they can be changed only in a writing signed by all parties, and some require specific signers, notice or the consent of a lender, landlord or other third party.

Signing an addendum: signatures, consideration and formalities

Who signs

An addendum binds only the parties who agree to it. As a rule, every party to the original contract should sign, even if the change mainly affects one of them. For a company, the signer should have authority to bind it. Each party should keep a copy of the signed addendum with its copy of the original contract.

"Changes must be in a signed writing" clauses

Many contracts include a clause saying they can be modified only by a written document signed by the parties. For sales of goods, Uniform Commercial Code section 2-209(2) generally gives effect to a signed agreement requiring signed modifications. If a merchant supplies the form to a nonmerchant, the nonmerchant must separately sign that requirement. Under section 2-209(4), an attempted modification that does not meet the signed-writing or statute-of-frauds requirements can nevertheless operate as a waiver. Article 2 has been adopted in some form in every state except Louisiana; check the applicable state's version. Outside the UCC, the effect of these clauses and any waiver or estoppel exception varies by state. Do not rely on that: put every change in a writing signed by all parties. Some contracts, such as contracts for the sale of land, must be in a signed writing under each state's statute of frauds, and a change to one of them should be in a signed writing too.

Consideration

Under traditional contract law, a promise to change an existing contract is binding only if it is supported by consideration: each side must give something new, not just what it was already obliged to do. A promise to pay more for exactly the same work, for example, can be challenged on that ground. The rule has been relaxed in several ways:

• Sales of goods. UCC section 2-209(1) says an agreement modifying a contract for the sale of goods needs no consideration to be binding, although the change must still be made in good faith.
• Unanticipated circumstances. The Restatement (Second) of Contracts, section 89, which many courts follow, treats a modification of a contract not fully performed on either side as binding without new consideration if it is fair and equitable in view of circumstances the parties did not anticipate when they made the contract.
• State statutes. Some states have statutes on this. In New York, for example, General Obligations Law section 5-1103 provides that a written contract modification signed by the party against whom enforcement is sought, or that party's agent, is not invalid merely because it lacks consideration. Other enforceability requirements still apply.

The practical answer is to make the addendum two-sided where you can (one side pays more, the other extends a deadline or adds work) and to say in the addendum what each side gives.

Electronic signatures and notarization

The federal E-SIGN Act and the Uniform Electronic Transactions Act, which most states have adopted, generally allow contracts and addenda to be signed electronically, with some exceptions, such as wills. An addendum does not usually need to be notarized. If the original document had to be notarized or recorded, for example a document recorded in the county land records, the change may need the same formalities.

Free contract addendum template (sample text)

Copy the text below into Word and fill in the brackets. It is an original, general US sample for adding or changing terms in an existing contract, not tied to any state or contract type. It is a starting point, not a finished document: check the original contract's amendment clause, and adapt the sample to the contract and your state's law.

Sample: addendum to an existing contract (fill-in template)

Copy addendum text

Not legal advice. This sample is not tailored to any state, contract type or transaction. Check the original contract's amendment and notice clauses, any third-party consents it requires, and your state's law before anyone signs.

Common examples of contract addenda

Lease addendum

Landlords and tenants use addenda to add a pet policy, parking or storage, a co-tenant or occupant, utilities, early termination terms or a rent change at renewal. For most housing built before 1978, federal law requires a lead-based paint disclosure, which is often attached as an addendum. Residential leases are also subject to state and local landlord-tenant laws, which can override lease terms, so an addendum cannot take away a tenant right that law makes mandatory. See the lease agreement template.

Purchase agreement addendum

In home sales, addenda commonly add or change contingencies (financing, inspection, appraisal, sale of the buyer's home), repairs or credits after an inspection, the closing date or the price. Many state real estate associations publish standard addendum forms. Because contracts for the sale of land must be in a signed writing, any change should be signed by every buyer and seller. For sales of goods between businesses, see the purchase agreement review guide.

Employment agreement addendum

Employers use addenda for a new commission or bonus plan, a remote-work arrangement, a change of role or pay, or new confidentiality or intellectual property terms. Adding a non-compete or similar restriction during employment needs care: states differ on whether those restrictions are enforceable at all, and on whether continued employment alone is enough consideration for one added after hiring. See the employment agreement template.

Common mistakes with contract addenda

• Not identifying the original contract. Without the title, date and parties of the contract being changed, it can be unclear what the addendum applies to.
• Vague changes. "Section 4 is updated to reflect the new pricing" invites a dispute. Quote the new text in full.
• Wrong section numbers. A change that points at the wrong section, or at a section renumbered by an earlier addendum, can change the wrong term.
• Missing signatures. An addendum signed by only one side, or by someone without authority, may not bind the other party.
• Ignoring the amendment clause. If the contract requires changes in a signed writing, notice or a third party's consent, follow it.
• Conflicting addenda. Several addenda on the same point without a clear order of precedence. Number them and say which controls.

How to draft or review a contract addendum in Word with LexDraft

LexDraft is a Word add-in from Microsoft AppSource. It opens as a side panel in Word 365 (Windows and Mac), Word 2021 and Word on the web, so the addendum stays in the document you are already editing.

What LexDraft does not do: it does not give legal advice, confirm that a change is enforceable in your state, or collect signatures. You check every output, including that each section reference matches the original contract, before anyone signs.

Reviewing an addendum someone else drafted?

• Lease review guide
• Purchase agreement review (UCC Article 2)
• Contract review checklist: 20 points