The California one action rule, set out in Code of Civil Procedure Section 726, limits a mortgage lender to a single lawsuit when collecting a debt secured by real property.1California Legislative Information. California Code CCP 726 If you default on a home loan, your lender cannot file one lawsuit to foreclose on the property and a separate lawsuit to chase you personally for the remaining balance. Everything happens in one action, and in most residential cases, that single action is where the lender’s rights against you end.
What the Rule Requires
Section 726 says there can be only one form of action to recover a debt secured by a mortgage or deed of trust on real property.1California Legislative Information. California Code CCP 726 That action is a foreclosure. The lender forecloses on the property, applies the sale proceeds to the debt, and then, if the law still allows it, seeks a deficiency judgment for the balance.
Courts call the underlying principle “security first.” A lender has to exhaust the real property collateral before going after the borrower personally. Filing a straight breach-of-contract suit on a mortgage note, without foreclosing, violates the rule. Without this constraint, a lender could win a money judgment, garnish your wages, and still foreclose later — collecting twice on the same debt. The one action rule shuts that door.
Can the Lender Still Sue You for the Shortfall?
In most California home foreclosures, no. Two things determine the answer: which foreclosure method the lender uses, and whether your loan is a purchase money loan.
Non-Judicial Foreclosure
Most California foreclosures are non-judicial. The lender sells the property through a trustee sale without going to court.2California Courts. Your Rights in a Nonjudicial Foreclosure After a non-judicial foreclosure, the lender cannot pursue a deficiency judgment against you. Section 580d of the Code of Civil Procedure bars any deficiency collection after a trustee sale.3California Legislative Information. California Code CCP 580d If the auction price falls short of your loan balance, the shortfall is the lender’s loss. That trade-off is why non-judicial foreclosure is faster and cheaper for lenders but gives up any personal claim against you.
Section 580d does not protect guarantors or other sureties on the loan. If someone guaranteed your mortgage, the lender may still pursue that person.
Judicial Foreclosure
In a judicial foreclosure, the lender files a lawsuit and the court oversees the sale. This route is slower and more expensive, but it preserves the lender’s right to seek a deficiency judgment for the difference between the sale price and the outstanding debt.1California Legislative Information. California Code CCP 726 Because of the one action rule, the deficiency claim has to be included in the same foreclosure action, not filed later as a separate suit.
Section 580a imposes a fair-value limitation. The deficiency is calculated against the property’s fair market value at the time of sale, not the auction price. A lender who buys the property cheaply at its own sale cannot then sue you for an inflated shortfall.
Purchase Money Loans
Section 580b blocks any deficiency judgment on a purchase money loan, meaning a loan taken out specifically to buy your home.4California Legislative Information. California Code CCP 580b The protection covers a deed of trust or mortgage securing a loan used to pay all or part of the purchase price of a dwelling of four or fewer units, where the buyer occupies the property. If you bought your home with a standard mortgage and later default, the lender cannot pursue you personally for the balance. The shield applies to both judicial and non-judicial foreclosures.
Section 580b also extends to refinances of purchase money loans, with one limit. If the refinance included cash-out or new principal beyond what was owed on the original purchase money loan, the lender can seek a deficiency on that new-advance portion.4California Legislative Information. California Code CCP 580b If you refinanced a $300,000 purchase money mortgage and pulled out $50,000 in cash, that $50,000 is not protected.
Between Section 580b and Section 580d, most California homeowners end up protected from any personal deficiency claim after foreclosure. A home equity line of credit or a cash-out refinance that falls outside 580b is still shielded by 580d as long as the lender forecloses non-judicially.
When a Separate Action Is Still Allowed
The one action rule is broad, but not absolute. A handful of situations let a lender bring a separate claim without violating Section 726.
Environmental Indemnity Claims
Section 736 allows a lender to bring a separate breach-of-contract action to enforce environmental provisions in a loan agreement, outside the foreclosure case. Commercial loan documents almost always include environmental indemnities covering cleanup costs. Section 736 lets those claims travel on a separate track rather than being trapped inside, or lost by, the foreclosure.
Sold-Out Junior Lienholders
When a senior lender forecloses, the sale wipes out junior liens. A second mortgage holder whose lien is extinguished this way is a “sold-out junior.” California courts have generally held that a sold-out junior can sue the borrower for the unpaid balance, because the foreclosure sale did not happen under the junior’s deed of trust.3California Legislative Information. California Code CCP 580d Section 580d only blocks deficiency judgments when the property was sold under the specific deed of trust securing the note being enforced.
If the same lender holds both the senior and junior loans, courts look more closely. Where the two loans were structured as a single transaction to expand the lender’s recovery rights, a court may block the junior deficiency to prevent an end-run around the anti-deficiency statutes. The exception works most cleanly when the senior and junior debts are truly separate, made at different times by different lenders.
Deed in Lieu of Foreclosure
A borrower who voluntarily transfers the property to the lender through a deed in lieu of foreclosure avoids the standard foreclosure process. Because no foreclosure sale occurs, Section 726 is not triggered the same way. A deed in lieu does not automatically wipe out the remaining debt. Unless the written agreement includes a full release of the balance, the lender may still try to collect. Negotiate the release in writing before signing.
What Happens If a Lender Breaks the Rule
A lender who ignores the one action rule and files a separate lawsuit on the note loses the security interest in the property. Courts treat the separate suit as an election of remedies. By suing on the note instead of foreclosing, the lender is deemed to have abandoned the mortgage, converting itself from a secured creditor into an unsecured one.1California Legislative Information. California Code CCP 726
That shift matters. A secured creditor has priority over the property and can force its sale. An unsecured creditor stands behind every secured claim and often recovers very little, especially in bankruptcy. The lender cannot undo the mistake by later trying to foreclose. The security interest is gone.
If a lender files a prohibited second action against you, the one action rule is an affirmative defense. Courts may dismiss the lender’s claim and leave the lender with higher legal costs, a weaker position, and no path back to the collateral.
Can the Rule Be Waived?
Commercial loan documents sometimes include language purporting to waive the one action rule. The law here is less settled than many lenders assume. A borrower cannot waive the one action rule or fair-value protections at the time the loan is made or renewed. Whether a borrower can waive these protections later, during a workout or loan modification, is an open question California courts have not definitively resolved.
If a lender asks you to sign a waiver of the one action rule as part of a loan modification, do not assume it will hold up. Talk to an attorney before agreeing. A modification structured to comply with the rule is more durable than one that leans on a waiver whose enforceability is uncertain.