Once a contract is signed and sealed, it’s set in stone — or is it?
Things often change, and knowing how to write an addendum to a contract can be a valuable skill in many situations.
Let’s explore what an addendum to a contract is and how you can write one in 7 easy steps.
Key takeaways:
- The goal of an addendum is to modify, clarify, or add new terms or conditions to an existing contract without creating an entirely new agreement.
- The key steps in writing an addendum to a contract are mirroring the language of the original agreement, specifying involved parties, clarifying the part of the contract the addendum refers to, ensuring compliance, and seeking legal advice when required.
- You can streamline and simplify the process of writing an addendum to a contract using sales and document management software.
What is an addendum to a contract?
An addendum to a contract is a legally binding document that is added to an existing legal contract.
Once a contract is signed, it’s usually difficult to change it without invalidating it. An addendum avoids the need to create a whole new contract, allowing parties to introduce new clauses while keeping the original contract intact.
And since it’s legally binding, an addendum can alter any terms and conditions of the original contract.
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Does an addendum have to be notarized?
Most of the time, an addendum can be legally valid without being notarized. For enforceability, the important thing is to have all parties to the original contract sign and agree to the terms of the addendum.
Here are a few things to consider, though:
- Contract terms or local law: The addendum should be notarized if the original contract specifically requires modifications to be notarized.
- Certain types of agreements: Some contracts, like real estate deeds or long-term lease agreements with specific jurisdictional requirements, might have to abide by state or local laws that require notarization to be enforceable.
- Added protection: Even if it’s not technically required, having an addendum notarized will give you extra verification that signatures are authentic, which can help avoid disputes later on.
So, the bottom line is that notarization is usually optional for an addendum unless applicable laws or the original contract demands it (although, it’s probably a good idea if you want to be extra safe.)
Who typically drafts an addendum?
Any party involved in the contract can draft an addendum. But it’s most commonly prepared by the following:
- One of the contracting parties if they mutually agree on changes
- A legal professional or attorney; this helps make sure the addendum is legal and compliant with applicable laws
- Agents or brokers in some specific industries will draft an addendum on behalf of a client (but recommended to do so under legal guidance)
All parties to the original contract have to agree to and sign the addendum for any changes to be legally binding.
What is the difference between an amendment and an addendum?
Many people confuse the terms contract addendum and contract amendment.
The difference between them lies in how they interact with the original contract:
- A contract amendment changes clauses or sections of an existing contract.
- An addendum is a separate document that extends the terms and conditions of a contract but does not change the existing text.
Both amendments and addendums involve, and therefore must be agreed upon, by all parties to the contract in order to be valid.
How to write an addendum to a contract
1. Mirror the language of the original contract
While an addendum is its own document, its purpose is to update or correct an original contract.
As such, it should mirror that original document as much as possible.
Be sure to continually refer to the contract when drafting an addendum. In particular, consider the contract’s:
- Language
- Formatting and layout
- Font and style
As far as possible, match all of these in the addendum.
That way, no parties should doubt that the addendum is as important and as relevant as other clauses of the contract.
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2. Choose an addendum title
Your addendum needs to clearly indicate what changes it makes and to which original contract. The first place you can do this is in your addendum title.
Give the addendum a title that references the original agreement’s name and date, and make it clear that it is indeed an addendum to that agreement.
For instance, perhaps you’re drafting an addendum to a residential lease agreement originally signed on the 1st of January 2021. Your addendum title might be:
“Addendum to Residential Lease Agreement Between [Your Name (owner)] and [Lessee’s Name (tenant)] of 1st January 2024.”
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3. Specify the parties
As the title suggested above shows, it’s crucial to specify the parties, which usually mirrors those listed in the original document. This ensures that everyone understands who is party to the addendum.
If a third party has an interest in the contract addendum, make sure to clearly mention their involvement.
4. Clarify the part of the original contract the addendum refers to
Addenda update an existing agreement, so they usually refer to a specific part of the original contract.
You should cite the title of any clause an addendum relates to and use font styles like italics, bold, and strikethrough to make clear what’s being replaced or modified.
For instance, say you are writing an addendum to a car rental lease agreement to change details of the vehicle.
Part of your addendum may look like this:
Original “Identification of Rental Vehicle” element of the Agreement:
Make: Ford
Model: Fiesta
VIN: 12345678
Color: Red
Year: 2020
Modifications proposed by this Addendum:
Make: Ford
Model: Fiesta Focus
VIN: 12345678
Color: Red
Year: 2020
5. Ensure compliance with the original contract and all relevant regulations
To make sure your addendum is fit for purpose and binding, it must not go against the original terms or requirements of the contract itself.
It should also comply with all laws and regulations in your jurisdiction.
It’s vital to check this before asking any parties to agree to the addendum.
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6. Add any additional elements
As well as the details sketched out above, most addenda will need to include some other elements:
- The effective date of the addendum;
- Relevant force majeure circumstances if not already covered in the original;
- A signature block to sign and date the addendum, either physically or with an eSignature;
- Disclaimers or other similar clauses, if required.
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7. Consider seeking legal advice
Finally, it’s worth considering seeking the advice of a law firm or legal professional before you present the addendum to the relevant parties.
This could help you keep the addendum from falling foul of laws or regulations, even those you may not be aware of.
What is an example of an addendum?
An addendum is typically used to introduce new terms/information to an existing contract without changing the original agreement. It only becomes legally binding when all parties review and sign it.
Here’s an example:
Say a company signs a service contract with a marketing agency for social media management. While partway through the contract, the client decides they want to add email marketing services.
Instead of having to rewrite the entire contract, the parties involved create an addendum that outlines the new scope of work, pricing, and timelines.
It might look something like this:
Addendum to Service Agreement
This Addendum is entered into on January 15, 2026, and amends the Service Agreement dated October 1, 2025, between ABC Company and XYZ Marketing Agency.
The following services are hereby added to the original agreement:
- Monthly email campaign strategy and execution
- List segmentation and automation setup
- Performance reporting
All other terms and conditions of the original agreement remain unchanged and in full effect.
Signed:
ABC Company Representative
XYZ Marketing Agency Representative
Here are some more examples of addenda:
- Adding new services or deliverables to a contract
- Extending a project deadline or contract term
- Updating payment terms or fees
- Including additional clauses (e.g., confidentiality or compliance requirements)
- Adding property details or contingencies in real estate agreements
Addendum to contract sample scenarios
An addendum to a contract can be used in various scenarios. Let’s explore some.
1. Addendum to an employment contract
Employment agreements can be lengthy documents, and it can often be the case that some clauses and details are left out either intentionally or unintentionally.
An addendum to an employment contract offers an opportunity to remedy such omissions or to add new details to remedy clauses in the original contract that may have been contentious.
A good example of a case when an addendum to an employment contract is needed is when the original contract’s clause regarding termination of employment only included death or employee resignation.
An addendum could be added later that also includes other grounds for termination, such as gross misconduct, breach of contract by the employee, or scenarios where the company is suffering financially and has to make compulsory redundancies.
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2. Addendum to alter insurance coverage
Another type of contract that often needs addendums is a contract for insurance coverage.
There are many scenarios in which an addendum to an insurance contract may be required; for example, state laws regarding insurance sometimes undergo changes.
As well as factors directly related to insurance, there’s also the aspect of data protection.
An addendum may be needed to reflect changes to the regulatory framework and compliance requirements surrounding how a company handles a customer’s confidential information.
3. Addendum for real estate purchase contracts
The real estate sector is one where there’s a frequent need for addendums to original contracts.
There are multiple scenarios where the details in the first signed agreement change and an addendum is needed to update them and keep the contract legally binding.
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Some of those scenarios include:
Extension of the closing date
If problems arise, such as with the buyer’s financing or with the sale of the buyer’s own property, the buyer and seller can agree to an extension.
Escrow holdback
An agreement may be put in place so that full payment can be withheld until certain tasks are carried out by the seller.
Inspection contingency
The buyer may choose to add an inspection contingency addendum so that if any inspection reveals issues with the property, they can withdraw from the sale or request that the issues be resolved.
Seller financing
In some cases, such as with developers, the seller may agree to grant the buyer a mortgage.
A contract addendum could include all details of such financing, such as the repayment period and monthly payments.
Short sale
If the seller of a property owes more money on it than the current market value, this addendum directs the seller to field offers on the property but also to seek their creditor’s consent to accept an offer.
Purchase-agreement termination
This addendum type may be needed when there’s a mutual agreement to cancel the sales contract and recognizes that neither party holds the other at fault.
It may also cover details regarding the return of a deposit and when that return should take place.
Write an addendum to a contract with a user-friendly PandaDoc template
Writing an addendum can sound like a complicated process, but it doesn’t have to be.
And while you may want to use an attorney for more complicated addendums, in most cases, creating an addendum is an exercise you can carry out yourself as long as you’re aware of what an addendum to a contract should look like.
What can make the process even easier is using a contract addendum template from PandaDoc. It can be used in any scenario where one or more parties want to change certain details of the original contract.
A great benefit of using one of our templates is that it takes care of all the tricky legalese that is needed in such documents and allows you to focus on the details you need to change or rectify.
While a template removes the need for legal expertise, you may still have to double-check some details, such as compliance with relevant laws.
By following the guidelines above and ensuring that all changes have been agreed upon, you’ll find that what could be a complicated process is extremely simple, and can be accomplished without an in-depth knowledge of contract law.
Whether adding an addendum to an employment contract or adding new terms agreed upon with a client, PandaDoc makes it as easy as A, B, C.
FAQ
Can you add an addendum after signing a contract?
Yes, an addendum can be added after a contract is signed, as long as all parties agree to the new terms. The addendum needs to reference the original contract, clearly outline the changes, and then be signed by all parties involved. Then, the addendum becomes part of the original contract and is legally binding.
