Waiver and Equitable Estoppel: Can You Still Enforce a Contract Term You Let Slide?

Last updated: November 2026. Reviewed by Pavel Kolmogorov, California business litigation attorney (State Bar No. 321018).

Waiver is the intentional giving up of a known contract right. Equitable estoppel bars a party from contradicting what it deliberately led the other side to rely on. (Evid. Code, § 623.) A California business that keeps accepting late payments may be found to have waived the deadline, so terminating without warning is risky. Notice that strict performance will be required can restore the right for future performance. A no-waiver clause helps but does not end the argument. Kolmogorov Law, P.C. litigates these disputes for businesses.

Call (909) 235-6116 or contact us online to discuss a contract right you want to enforce after letting it slide, or a term the other side has suddenly started to enforce.

Waiver: giving up a right you knew you had

The California Supreme Court defines waiver as the intentional relinquishment of a known right after knowledge of the facts. The party claiming a waiver must prove it by clear and convincing evidence, and doubtful cases are decided against a waiver. (Waller v. Truck Ins. Exchange, Inc. (1995) 11 Cal.4th 1, 31.)

A waiver may be express, based on what the party said. It may also be implied from conduct that shows an intent to give up the right. (Ibid.) The court described the conduct that qualifies: acts so inconsistent with an intent to enforce the right that they induce a reasonable belief the right has been relinquished. (Id. at pp. 33-34.)

Not every right can be waived. Anyone may waive the advantage of a law intended solely for their benefit, but a law established for a public reason cannot be contravened by a private agreement. (Civ. Code, § 3513.)

Equitable estoppel: the other side relied on you

A party that has, by its own statement or conduct, intentionally and deliberately led another to believe a particular thing true and to act on that belief may not contradict it in litigation arising from that conduct. (Evid. Code, § 623.)

The difference from waiver is reliance. Estoppel requires proof that the other party relied to its detriment. (Waller, supra, 11 Cal.4th at pp. 33-34.) Waiver asks what the party holding the right intended. Estoppel asks what the other party did because of it.

A related doctrine is covered on our page about promissory estoppel.

Accepting late payments or late deliveries

A licensee sends its royalty reports six weeks late for six quarters, and the licensor says nothing. On the seventh, the licensor declares a default and terminates.

The Commercial Code has a rule for the transactions it governs, such as sales of goods. (Com. Code, § 1102.) A course of performance exists when an agreement involves repeated occasions for performance and the other party, knowing the nature of the performance and having an opportunity to object, accepts it or acquiesces without objection. (Com. Code, § 1303, subd. (a).) A course of performance is relevant to show a waiver or modification of any term inconsistent with it. (Com. Code, § 1303, subd. (f).) For a contract outside that code, which the license above may be, the waiver rule already described applies.

Acceptance is evidence, not an automatic result, because the question is still intent. A written objection and reservation of rights with each late payment is evidence the other way.

What a no-waiver clause does

A no-waiver clause says that accepting late or defective performance is not a waiver, and sometimes that no waiver is effective unless written and signed. The Court of Appeal has said such a provision weighs against a finding of waiver in most circumstances. It also noted that the landlord in the case cited no authority that such a provision cannot itself be waived. (Gould v. Corinthian Colleges, Inc. (2011) 192 Cal.App.4th 1176, 1180.)

A commercial tenant had to make its early termination payment in cash or immediately available funds. It paid most of the sum by check and applied part of its security deposit to the rest. The landlord kept the money, then argued the termination had failed and pointed to the lease's antiwaiver clause. The court upheld the finding of waiver.

For goods, a signed agreement between merchants that requires modifications to be in a signed writing or other signed record cannot be modified another way. (Com. Code, § 2209, subd. (2).) Yet an attempted modification that fails that requirement can still operate as a waiver. (Com. Code, § 2209, subd. (4).) For other contracts, the statute on modifying written agreements expressly preserves the rules on waiver and estoppel. (Civ. Code, § 1698, subd. (d).) Our page on integration clauses and contract modification explains how the pieces fit.

How to restore strict performance

In a sale of goods, a party that waived an executory part of the contract may retract the waiver by reasonable notification, received by the other party, that strict performance will be required. The exception is where retraction would be unjust because the other party materially changed its position in reliance on the waiver. (Com. Code, § 2209, subd. (5).)

The California Supreme Court reached a similar result for a land contract long ago, as our page on time is of the essence clauses explains.

The notice should be in writing and specific. Name the term, state the date from which it will be enforced, and allow enough time to comply. Then enforce it every time. Accepting the next late payment without a written reservation invites a new waiver argument.

If you want to enforce a term you let slide

Do not terminate first and explain later. A termination based on a waived deadline may itself be a breach, a risk covered on our page about material and minor breaches. Send the notice described above, wait for the next default, and follow the contract's cure procedure. We read the notice and default clauses first, because they control the sequence.

If a term is suddenly enforced against you

Collect the history: every late payment or delivery that was accepted, and what the other side said each time. Show what you did in reliance, such as commitments made on the assumption that the practice would continue. If the dispute involves a condition to the other side's own duty, see our page on conditions precedent.

What to bring to the first meeting

The contract, including any no-waiver, notice, cure, and amendment clauses.
A ledger or log of due dates and the dates performance was received.
Every email, letter, or notice about lateness, including reservations of rights and any default or termination notice.
Evidence of what either side did in reliance on the past practice.

Frequently asked questions

We accepted late payments for a year. Can we still terminate the contract for late payment now?

Not safely, without notice. Under California law a year of accepting late payments without objection can support a finding that you waived strict timing. You can restore the deadline for future payments by notice that strict performance will be required. A termination based on a later default, after that notice, stands on firmer ground.

What is the difference between waiver and estoppel?

Waiver is the intentional giving up of a known right, and California courts focus on the intent of the party who held the right. Estoppel focuses on the other party. It applies when one side's statements or conduct led the other to believe something and to act on it, and it requires detrimental reliance.

Does a no-waiver clause prevent waiver in California?

It makes waiver harder to prove but does not rule it out. A California appellate court has said such a clause weighs against a finding of waiver in most circumstances. The same court upheld a finding that a landlord who kept a tenant's payments had waived the clause itself. Written objections made at the time support the party relying on the clause.

Our customer always paid late and we never complained, but our contract says no waiver unless in writing. Are we protected?

Partly. The clause weighs against a finding that you waived the payment date. A long record of silent acceptance cuts the other way, because a California court has held that the clause can itself be waived, and the customer may also argue estoppel if it relied on the practice. Send written notice restoring the deadline before you act on a late payment.

What is equitable estoppel in California?

Equitable estoppel prevents a party from contradicting what it intentionally and deliberately led another to believe, when the other acted on that belief. California codifies the rule in Evidence Code section 623. In contract disputes it is raised against a party that tolerated a practice and then tried to enforce the written term without warning.

Talk to a California breach of contract attorney

If your business needs to enforce a contract term after a period of leniency, or is facing a termination over a term that was never enforced, call (909) 235-6116 or contact us online. Kolmogorov Law, P.C. is a business litigation firm in Irvine, California, that represents companies and their owners in court and in arbitration.

This page provides general information about California law and is not legal advice. Outcomes depend on the contract, the parties' conduct, and the court.