Addendum

Key Takeaways

• An addendum is attached when the contract is written and becomes part of the binding agreement once the parties sign it.
• An amendment changes a term of a contract that already exists, while an addendum adds terms as the contract is being formed.
• An attachment that the parties never signed is not part of the agreement, so signatures on the addendum matter as much as signatures on the main form.
• In Washington, the seller disclosure statement is a statutory disclosure delivered under RCW 64.06.020 rather than an addendum, and the statute says it is not part of the purchase agreement.

What It Means

An addendum is a separate page attached to a contract that spells out terms the main form does not cover. Preprinted purchase and sale forms are built to handle the common case, so anything unusual, whether a specific repair, an unusual financing arrangement, or a condition on the sale of the buyer's current home, is written on an addendum and attached. Because the addendum is included when the contract is written and signed by the parties, it carries the same force as the printed pages.

Addenda are how most Contingency language reaches the agreement. An inspection contingency, a financing contingency, and an Escalation Addendum that raises a buyer's price automatically against competing offers all arrive as attachments. The distinction to hold onto is timing. An addendum is part of the deal from the start. An amendment comes later, after a contract already exists, and changes something the parties previously agreed to. Both need every signature, since neither one binds a party who did not sign it.

How It Works in Washington

In Washington, an addendum is bound by the same writing rule as the contract it joins. RCW 64.04.010 requires every conveyance of real estate, or any interest in it, to be by deed, and RCW 64.04.020 requires a deed to be in writing and signed by the party bound. That is why terms affecting a Washington sale are captured on signed paper rather than left in an email thread or a phone call, and why brokers attach an addendum instead of writing a side agreement.

One Washington document that students miscategorize is Form 17, the seller disclosure statement. RCW 64.06.020 requires the seller of improved residential real property to deliver it not later than five business days, unless otherwise agreed, after mutual acceptance, and the statute states that it is a disclosure and does not constitute part of the purchase agreement. So Form 17 is a statutory delivery obligation, not an addendum. It gives the buyer a rescission right rather than adding a contract term, and it changes nothing the parties negotiated.

Example

Priya and Sam offer $525,000 on a Vancouver, Washington house with $15,000 in earnest money. Two addenda go in with the offer at signing: an inspection contingency giving them 10 days to review the property, and a financing contingency tied to their loan approval. Both are signed by all four parties, so they are part of the Purchase And Sale Agreement from the moment of mutual acceptance, exactly as if the terms had been printed on the form.

The inspection turns up a failing water heater. The parties negotiate and sign a document reducing the price by $8,000, to $517,000. That one is an amendment, not an addendum, because it changes a term of a contract that already exists. Both documents end up in the same file and both bind the parties, but only the two signed at the outset were addenda.

Common Mistakes and Exam Traps

• An addendum adds terms when the contract is formed; an amendment changes terms after the contract exists. Exam questions swap the two words on purpose.
• A contingency is a condition inside the agreement, while an addendum is the document that can carry that condition, so the two are not interchangeable.
• An addendum signed by only one side is not binding, because a contract term needs the assent of every party it binds.
• The Washington seller disclosure statement is a required disclosure under RCW 64.06.020, not an addendum, and it does not become part of the purchase agreement.