C.A.R. Form ASA, the Additional Signature Addendum published by the California Association of Realtors, gives you extra signature lines when a real estate contract has more signers on one side than the primary form can hold. Most C.A.R. contracts, including the Residential Purchase Agreement, only fit two buyers and two sellers. Anyone beyond that signs on the ASA, which attaches to the primary contract and carries the same header information so the two documents read as one.
When You Need It
The trigger is usually a headcount problem. Three siblings selling an inherited house, a couple buying with a parent, or a group of investors acquiring a rental all put more names on one side of the deal than the standard form accommodates.
Business entities need the ASA when their governing documents require more than one officer to authorize a sale. An LLC with two managing members may need both signatures, and each signer gets a dedicated line with a title field so their corporate role is documented.
Trusts with co-trustees are another common case. When property is held in a trust that requires the co-trustees to act together, each trustee signs, and the signature block should match the property’s vesting: name, capacity as trustee of the named trust, and the trust date.
Power-of-attorney arrangements fit here too. If an agent signs for someone who cannot sign personally, the “Other” checkbox and title field let the agent identify themselves and the principal they represent.
Filling In the Header
The top of Form ASA ties the addendum to the original contract. Three pieces of information go here:
- Document type. Check whether the addendum supplements a Residential Purchase Agreement, a Residential Listing Agreement, or another document. If you check “Other,” write in the name of the contract.
- Date. Enter the date the original contract was signed, not today’s date. This links the addendum to the specific agreement it modifies.
- Property address. The full street address exactly as it appears on the primary contract.
The header also identifies the parties to the original transaction by role: Buyer, Seller, Landlord, Tenant, Broker, or Other. Match these to the primary contract. A wrong date or a slightly different property description creates ambiguity about which contract the additional signers are joining.
Completing Each Signature Block
The form provides three identical signature blocks. Each one collects the following for a single additional party:
- Role checkbox. Mark Buyer, Seller, Landlord, Tenant, or Other.
- Printed name. The signer’s full legal name, matching their government-issued ID or the name on the property’s vesting deed. Misspellings and missing middle initials cause delays when the title officer or notary compares signatures to the title report.
- Title, if applicable. For anyone signing in a representative capacity (a corporate officer, LLC member, trustee, or attorney-in-fact), write the title here. A trustee, for example, would enter “Trustee of the [Trust Name], dated [date].”
- Signature and date.
If you need more than three additional signatures, use a second copy of the form. There is no limit on how many addenda you can attach, but each one must repeat the header information so it independently references the original contract.
Arbitration and Liquidated Damages Initials
Each signature block on the ASA also asks whether the signer agrees to the arbitration provision and the liquidated damages provision in the primary contract. This step is easy to miss.
If the original Residential Purchase Agreement contains an arbitration clause that the original parties already initialed, each additional signer on the ASA must separately initial whether they agree or do not agree. The same applies to any liquidated damages clause. The form provides paired “agree” and “do not agree” checkboxes for each provision. Leaving them blank does not default to agreement; it creates an ambiguity that can surface in a dispute.
Before handing the form to additional signers, check whether the original parties initialed these clauses on the primary contract. If they did not, the ASA’s arbitration and liquidated damages sections can be left blank.
Signing and Dating
Form ASA can be signed with wet ink or electronically. California’s Uniform Electronic Transactions Act provides that an electronic signature satisfies any legal requirement for a signature, and a contract cannot be denied enforceability solely because an electronic record was used in its formation.1California Legislative Information. California Civil Code 1633.7 DocuSign and Authentisign are widely used in California real estate for this purpose.
Every signature must include the date the signer executed the form. When multiple people sign on different days, each dates their own block. Those dates matter, because a purchase agreement is not fully ratified until every required party has signed, and a missing date creates uncertainty about when the contract became binding on that individual.
Attaching the Addendum to the Primary Contract
California Civil Code Section 1642 provides that several contracts relating to the same matters, between the same parties, and made as parts of substantially one transaction are to be taken together.2California Legislative Information. California Civil Code 1642 – Interpretation of Contracts In practice, the ASA and the primary agreement function as a single integrated contract, and agents keep them in the same document package (a stapled physical set or a single digital transaction file) so there is no question about which documents belong together.
Once fully signed, distribute copies to every party. Escrow needs the addendum to verify who is authorized to sign closing instructions and approve fund disbursements. The other side needs a copy to confirm the contract is fully ratified. On a digital platform, upload the signed ASA to the same transaction folder as the primary agreement.
What a Missing Signature Costs
Skipping a required signature can derail the transaction. Under California’s Statute of Frauds, an agreement for the sale of real property is invalid unless it is in writing and signed by the party to be charged.3California Legislative Information. California Civil Code 1624 If one of three co-owners never signs the purchase agreement or the ASA, the contract may be unenforceable against that person, and because they hold an ownership interest, the property cannot transfer cleanly without their consent.
Title companies catch this during their review. A preliminary title report lists every person or entity with a recorded interest in the property, and the title company will not issue a policy until every listed owner has signed. A missing signature creates what the industry calls a cloud on title, an unresolved question about ownership that prevents the title from being considered marketable. Until the cloud is cleared, the lender will not fund the loan and the deal will not close.
The simplest way to avoid this is to pull the preliminary title report early and compare it against your list of signers. If someone on the title report is not already a party to the primary contract, prepare an ASA for them before the deal reaches escrow. Chasing down a missing signature at the last minute, particularly when a signer is out of state or unavailable, is one of the most common reasons California closings get delayed.
Where to Get the Form
Form ASA is a proprietary C.A.R. document available to California Association of Realtors members through the zipForms platform, accessed via the C.A.R. member portal. The platform auto-populates property data and party names from the primary transaction, which reduces manual entry errors. Non-members, including buyers and sellers acting without an agent, cannot directly download C.A.R. forms. In a for-sale-by-owner transaction you can draft your own additional signature page, but title companies and escrow officers are accustomed to the standardized ASA format and may flag a homemade substitute for review.