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A contract is signed, but something needs to change. Maybe you need to add a new set of specifications. Maybe the payment date has moved. Either way, rewriting the whole agreement creates extra work and slows things down.
That’s where an addendum or amendment can help. The basic difference is simple: An addendum adds new material without modifying substantial existing terms, while an amendment changes terms that are already there.
A useful way to think about it is: Am I adding something new, or changing something we already agreed to?
If you’re adding technical specifications that weren’t covered before, you might need an addendum. If you’re changing an existing 30-day payment term to 45 days, you might need an amendment.
Once you know which document you need, check what the original contract and applicable law require, prepare the change, and get any necessary approvals and signatures.
This guide walks you through that process.
Disclaimer: This information is for general purposes only. It isn’t legal advice and shouldn’t replace counsel from a licensed attorney.
The UCC discussion in this guide concerns contracts for goods and follows the uniform text. States enact their own versions, and the enacted language might differ.
Addendum vs amendment at a glance
If you have the original contract in front of you, start by looking at what you want to do to it.
The document’s title doesn’t necessarily settle the question. Say a vendor sends you “Addendum No. 2,” but the document replaces an existing payment term. Calling it an addendum doesn’t change what the document actually does. You still need to look at its substance, the original agreement, and the requirements that apply.
What is an addendum?
An addendum is an addition to a finished document. Cornell’s Legal Information Institute explains that an addendum is often an attachment or exhibit and “does not modify substantial terms of the document.”
Let’s say you’ve signed a supply agreement covering quantities, prices, and delivery dates. A few weeks later, you need to add detailed product specifications that weren’t included in the original.
Rather than rewriting the whole agreement, an addendum can give that additional material a clear home alongside it because you’re just adding material.
You might also come across exhibits, riders, and schedules. Those labels can serve different purposes, so check how your contract defines and uses them rather than assuming they’re interchangeable.
What is an amendment?
An amendment is used when what you need to change is already in the contract.
Say your agreement gives a customer 30 days to pay an invoice. You both decide to change it to 45 days. You’re changing an existing term, which points toward an amendment.
Cornell defines amend as making a change “by adding, subtracting, or substituting.” An amendment can identify the affected clause, state the replacement language, and make clear which parts of the original agreement stay as they are.
If you’re still working out whether you have a contract in the first place, our guide to the difference between a memorandum of understanding and a contract can help you get started.
How to tell whether you need an addendum or amendment
You don’t need to memorize contract terminology to make a useful first assessment. Put the proposed change next to the original agreement and work through these five questions:
- Are you changing an existing term? You might need an amendment.
- Are you adding material without changing a substantial existing term? You might need an addendum.
- Has the contract already been signed? If it hasn’t, make sure any addendum becomes part of the final agreement. If it has, check the contract’s process for later changes.
- What does the original contract say about changes? Look for provisions covering modifications, approvals, signatures, or required written changes.
- Could applicable law add other requirements? Governing law, jurisdiction, contract type, and the change you’re making can all affect what’s required.
Those questions can point you toward the document you might need. But they don’t determine whether a particular change will be legally effective.
Once you know what you’re preparing, think about the rest of the process too. Who needs to approve it? Who needs to sign? How will you know when they’re finished? And where will the completed document live alongside the original?
If you’re handling that process digitally, Dropbox Sign online contracts can help you prepare and send the document for signature and track the request’s progress. You’ll still need to decide the requirements that apply to your agreement.
How to write an addendum to a contract
If an addendum fits your situation, make its connection to the original agreement easy to understand.
Here’s a five-step starting point for how to write an addendum to a contract:
- Identify the original agreement by title and date: Make it clear which contract the addendum belongs to.
- Name the parties: Use the legal names from the original agreement.
- Describe the added material precisely: Include the details, dates, specifications, or other information you’re adding.
- Give the addendum an effective date: If it differs from the signing date, make the distinction clear.
- Check the approval and signature requirements: Review the original contract and applicable law to determine who needs to approve or sign the addendum and what formalities apply.
Where appropriate, you can also state that the rest of the original agreement remains unchanged.
If you regularly prepare similar documents, you probably don’t want to rebuild the signature request every time. With Dropbox Sign, you can create reusable templates, then only fill in the information that changes for each request.
That can be useful for recurring addenda where the structure stays consistent but the parties, dates, or added information change.
What does an addendum look like?
Suppose you need to add technical specifications to a signed supply agreement. Here’s a simplified example of what an addendum could look like:
ADDENDUM NO. 1
to the Product Supply Agreement dated March 14, 2026
This Addendum No. 1 (the “Addendum”) is entered into as of August 3, 2026, between [Buyer legal name] (“Buyer”) and [Supplier legal name] (“Supplier”), the parties to the Product Supply Agreement dated March 14, 2026 (the “Agreement”).
1. Product Specifications: Schedule A to this Addendum provides the technical specifications for the products described in the Agreement. Schedule A is incorporated into the Agreement.
2. No Other Changes: Except for the material added by this Addendum, all terms of the Agreement remain in full force and unchanged.
[Signature blocks for the parties required to sign under the Agreement and applicable law, including printed name, title, and date.]
Once the wording has been reviewed and you’re ready to send it, your document moves from drafting to coordination. Dropbox Sign can help you route the signature request to the appropriate signers, while automated reminders can reduce the manual work of following up.
DISCLAIMER: These documents are provided to users as a starting point for convenience. Using a template isn’t a substitute for legal advice from a licensed attorney, and the information contained in the document shouldn’t be construed as legal advice. Because the law differs in each legal jurisdiction and may be interpreted or applied differently depending on your location or situation, you shouldn’t rely on the materials provided here without first consulting an attorney about your specific situation. Dropbox Sign doesn’t make any representation as to the legal enforceability or effectiveness of any templates, or the resulting documents created using them.
Before you send it, check the original contract
You’ve drafted the change. Before sending it anywhere, pull up the original agreement again.
It might already tell you how changes have to be made, who needs to approve them, and whether they need to be signed or put in writing. Applicable law can add other requirements.
Check who needs to approve and sign
The parties need to agree to the change. Cornell refers to agreement by all parties to a contract as mutual assent.
Next, check who needs to sign and what formalities apply. Cornell’s addendum guidance says an addendum “should be signed or executed with the same formalities unless the original document states otherwise.”
That doesn’t mean every addendum has identical signature requirements. Follow the original contract and applicable law for your situation.
Check whether the change needs to be in writing
Sometimes the contract itself answers this question. If it says changes must be made in a signed writing, follow that process. Applicable law can also require a writing in certain circumstances.
For contracts involving goods, UCC rules may be relevant. Under the uniform text of UCC § 2-209, a modification must satisfy applicable statute-of-frauds requirements if the contract as modified falls within them.
For example, under the uniform UCC text, a sale of goods for $500 or more generally requires a sufficient signed writing to be enforceable. An informal $400 order that later increases by $150 might then cross that threshold.
State enactments can differ, and other writing requirements might apply to other types of contracts. Review the law that applies to your agreement.
Check whether consideration could be an issue
Consideration is the legal term for what each party gives or promises. Whether a contract change needs new consideration depends on the type of contract and applicable law.
For example, if someone has already agreed to perform a service for a set price, simply promising them more money to perform the same existing obligation can raise consideration issues.
Sales of goods follow a different rule under the uniform UCC text. UCC Article 2 says an agreement modifying a goods contract doesn’t need consideration to be binding, although other requirements can still apply.
This is a good example of why choosing the right document is only the first step. If you’re unsure what rules apply to your contract or proposed change, consult a licensed attorney.
What changes if the original contract hasn’t been signed yet?
Timing matters too.
If you’re adding material before the original contract is signed, make sure it becomes part of the final agreement instead of leaving it as a separate side document. Clearly identify the original agreement and explain how the documents relate.
One reason is the parol-evidence rule. When parties intend a signed writing to be their complete agreement, the rule can limit the use of earlier or simultaneous agreements that contradict or change its terms. Exceptions can apply.
An integration or merger clause can also state that the written contract is the parties’ complete agreement.
If the contract has already been signed, check its modification provisions and any requirements for making a later change.
What happens if you call the document the wrong thing?
Calling a document an addendum when it actually changes an existing term can make the intended change less clear.
What happens next depends on the agreement, governing law, and circumstances. The document’s title alone doesn’t determine whether an attempted change is effective.
For goods contracts, the UCC also says an attempted modification that doesn’t meet certain requirements may still operate as a waiver. Questions about waiver, retraction, reliance, and partial performance can depend heavily on the facts, so legal advice may be appropriate.
For your workflow, there’s a simpler lesson: Make the change easy to follow. Identify the original agreement, say exactly what you’re adding or changing, and follow the process the contract requires.
Your addendum is ready. What happens next?
Once the wording is settled, your job shifts from drafting the document to getting it completed.
Start by keeping the new document clearly connected to the agreement it belongs to. Then follow whatever approval and signature process the original contract and applicable law require.
Before you send it:
- Keep the documents connected: Clearly identify the original agreement and keep the completed addendum or amendment with it.
- Collect the required signatures: Check the original agreement and applicable law to determine the necessary approvals and signatures.
- Confirm electronic signing is appropriate: The federal ESIGN Act generally says that a signature, contract, or record can’t be denied legal effect solely because it’s electronic. It doesn’t require another party to accept electronic records or signatures.
- Check applicable disclosure and retention requirements: Different rules can apply depending on the transaction, parties, and jurisdiction.
If another law requires an electronic record to be kept, ESIGN requires the record to accurately reflect the information and remain accessible for the required period. ESIGN itself doesn’t create the retention obligation.
The administrative side can get repetitive, especially if you manage agreements regularly. With Dropbox Sign, you can add signer fields, send signature requests, automate reminders, and see where requests stand. When several documents are out for signature, that status visibility makes it easier to see what’s complete and what’s still waiting.
An electronic signature audit trail can also provide a record of activity associated with the signature request.
These tools help you manage the signing workflow. They don’t determine what your addendum or amendment needs to contain, whether it’s enforceable, or what retention requirements apply.
Does “addendum” mean the same thing everywhere?
Not necessarily. Legal terminology can vary across jurisdictions.
Cornell notes that in civil law systems, addendum can refer more broadly to a modification of a contract, rather than only an addition that leaves substantial existing terms unchanged.
If you’re working internationally, don’t rely on the document title by itself. Make clear what you’re adding or changing and which terms remain in place.
You can also review electronic signature laws around the world when considering a cross-border electronic signing process.
Send and track addenda with Dropbox Sign
When a contract needs updating, start with the simplest question: Are you adding something new or changing something that’s already there?
That can point you toward an addendum or amendment. From there, check the original agreement and applicable law, make the change explicit, and follow the required approval and signing process.
If contract updates are a regular part of your work, the administrative work around them can add up. Preparing a request, sending it, following up with signers, and checking whether it’s finished all take time.
Dropbox Sign gives you a simpler way to manage that part of the process. Reusable templates can help standardize recurring documents, automated reminders can reduce manual follow-up, and status visibility helps you see where signature requests stand.
If you’re looking to standardize recurring agreement workflows or spend less time chasing signatures, talk to our team about Dropbox Sign.
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What’s the difference between an addendum and an amendment?
An addendum generally adds material to a finished document without modifying substantial existing terms. An amendment changes existing terms by adding, removing, or replacing them.
If you’re not sure which one you need, compare the proposed change with the original contract. Are you adding something new, or changing something that’s already there?
Can an addendum be added before the contract is signed?
Yes. Make sure the addendum becomes part of the final agreement or is clearly incorporated into it.
The contract’s terms and applicable law can affect how this should be done, so check the requirements that apply before signing.
Do both parties have to sign an addendum?
The parties need to agree to the addition, but the signatures and formalities required depend on the original contract and applicable law.
Check both before you send an addendum for signature.
Is the plural addenda or addendums?
Both addenda and addendums are accepted plural forms of addendum. Merriam-Webster lists both.
If you’re dealing with several formal contract addenda, you might label them individually as “Addendum No. 1” and “Addendum No. 2,” then refer to them collectively as the addenda.
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