By Neta, founder of SortMyDivorce · Updated
There is a device in some jurisdictions that changes the economics of refusing a reasonable offer. It exists in Canadian family law. It largely does not exist in American family law. Advice written for one country is actively wrong in the other. This is the single most jurisdiction-dependent topic on this site. Sections below are marked with what has been verified and what has not. Do not act on any of it without your own lawyer.
| What a formal offer is | A settlement proposal made under a court rule, which can carry consequences for legal costs if it is refused and the refusing party does no better at the end. |
|---|---|
| Ontario | Governed by Rule 18 of the Family Law Rules. Verified 19 Aug 2026. |
| The Ontario consequence | If an offer is refused and the court result is as good or better for the offering party, "the person who didn't accept the offer may have to pay a part of the other person's legal fees." |
| A limit people miss | In Ontario, cost consequences and time limits apply to offers made in relation to motions or trials — not to case conferences or settlement conferences. |
| Ontario timing | To carry costs consequences at trial, an offer "must be made at least seven days before the trial." Verified from the Ontario Court of Justice, 19 Aug 2026. |
| Ontario signature | "The offer to settle must be signed by you and your lawyer (if you have one)." |
| United States — federal | FRCP 68 does not apply to divorce. Divorce is a state matter and federal courts do not hear it. |
| United States — state | Offer-of-settlement rules exist but are generally rules of civil procedure tied to damages claims. See the verification note — this is flagged as unverified. |
| Origin of "Calderbank" | Calderbank v Calderbank [1975], an English Court of Appeal case which was itself about divorce finances. |
| The transferable part | The concept: a documented, formal offer creates leverage and a record. |
| The non-transferable part | The mechanic: near-automatic costs shifting. That is not a general US feature. |
Keeping track of dates like these across a stack of letters is exactly what SortMyDivorce does — start a free trial, no card needed.
Most legal systems want cases to settle. Trials are expensive, slow, and hard on everyone involved — particularly in family matters, where the parties have to keep dealing with each other afterwards.
A formal offer to settle is a device for putting pressure on unreasonable refusal. The logic is simple: if one side makes a sensible proposal, and the other refuses it, and the eventual outcome is no better than what was proposed, then the refusing party caused everything that happened after the refusal. The costs of that period should arguably follow them.
That is the theory. How far it is implemented differs enormously, and that is where people get into trouble.
In Ontario family proceedings, offers to settle are governed by Rule 18 of the Family Law Rules.
An offer to settle is a proposal to resolve some or all of the issues in the case — support, property, parenting, or any combination. Parties can make offers at any point, including before the case begins, and can make more than one.
The costs consequence is the point of the exercise. As Steps to Justice, Ontario's public legal information service, puts it: if a party rejects an offer and the court result is as favourable or better for the offering party, "the person who didn't accept the offer may have to pay a part of the other person's legal fees."
Two limits are worth knowing, because they are frequently misunderstood:
It applies to motions and trials. Cost consequences and time limits under the rule apply to offers made in relation to motions or trials — not to case conferences or settlement conferences, where offers are discussed openly with the judge in any event.
"May", not "will". The consequence is discretionary rather than automatic. A court decides, and the circumstances of the case matter.
Two mechanical requirements, from the Ontario Court of Justice's own guide for self-represented litigants. The offer "must be signed by you and your lawyer (if you have one)." And to carry costs consequences at trial, "it must be made at least seven days before the trial." An offer made on the courthouse steps does not do the work.
There is also a partial-success provision worth knowing: "if you do better than the final decision on part of your offer that could have been accepted, you may be entitled to costs for that part." An offer does not have to be beaten in its entirety to be useful.
Verification note — Ontario. The text of Rule 18 itself could not be read directly: Ontario's e-Laws site requires JavaScript and CanLII blocks automated access. Everything stated above is taken from two accessible official sources — Steps to Justice, Ontario's public legal information service, and the Ontario Court of Justice's own published guide for self-represented litigants. On the question of a form: Steps to Justice states that no specific form is mandated, and the Court's own trial guide refers only to the offer being signed by the party and their lawyer, not to a numbered form. Some practitioner sources refer to a "Form 18". We have therefore not stated a form number. Confirm with your lawyer or on e-Laws before relying on any of this.
Formal offer mechanisms exist across Canada, but they are set by each province's rules and they differ — in the form required, the timing, the notice period, and the strength of the costs consequence.
Verification note — provinces other than Ontario. We have deliberately not set out the rule numbers, forms or deadlines for British Columbia, Alberta, or any other province. Our research identified plausible provisions but could not verify them against primary sources, and a wrong rule number on a page like this is worse than no rule number. Ask your lawyer what the formal offer mechanism is in your province and what it requires.
This is where imported advice does real damage.
Federal Rule of Civil Procedure 68 — the offer of judgment rule — is the provision Americans sometimes hear about in this context. It does not help you. FRCP 68 governs federal civil actions, and divorce is not heard in federal court. Domestic relations is a state matter, and the federal courts decline jurisdiction over it. Rule 68 essentially never touches a dissolution.
Most states have their own offer-of-settlement or offer-of-judgment provisions. These are generally rules of civil procedure, framed around claims for damages, and they generally do not govern dissolution proceedings.
Verification note — US states. This is the most significant gap in this guide, and we want to be explicit about it. Our research did not find a source that directly and authoritatively states that state offer-of-settlement rules exclude family law proceedings. The proposition is consistent with how those rules are framed — Florida's, for example, is tied by statute to a "civil action for damages", which a dissolution is not — but we did not verify the exclusion itself. If you are in the United States, ask your lawyer whether your state has any offer mechanism that applies to a divorce. Do not assume from this page that it does not.
What the US does use instead. Rather than costs shifting on refused offers, American family courts generally address fees through two different routes: need-and-ability-to-pay fee awards, under provisions like California Family Code sections 2030 and 2032 or New York Domestic Relations Law section 237; and sanctions for conduct. California Family Code section 271 is the closest functional cousin to a costs consequence, because it expressly targets conduct that frustrates settlement.
Verification note. The statutory citations in the preceding paragraph were not independently verified for this guide. They are included as signposts for a conversation with your lawyer, not as statements of law.
The term "Calderbank offer" comes from Calderbank v Calderbank [1975], a decision of the English Court of Appeal — and, appropriately enough, a case about the financial consequences of a divorce.
The mechanism it created spread through the Commonwealth. In Australia it remains standard in family law. In England and Wales it has been substantially curtailed in financial remedy proceedings, where a general "no order as to costs" rule now applies and open offers carry the weight instead.
Verification note. We could not verify the current English position on costs and failure to negotiate openly. It is included here for context only. Anyone dealing with an English matter should take English advice.
Strip out the jurisdiction-specific machinery and something useful remains, and it applies everywhere.
A documented, specific, reasonable offer changes the dynamic — whether or not a rule attaches consequences to refusing it. It moves the conversation from posturing to a concrete proposal that has to be accepted, refused, or countered.
A record of reasonable conduct is worth having. In most systems, how the parties behaved is relevant to costs in some form, even where there is no formal offer rule. Being able to show a sequence of specific, justified proposals — and their refusal — is a stronger position than being able to say you were reasonable.
Refusal becomes a decision rather than a drift. A formal offer with a response window forces the other side to engage. That is often its main practical value.
What does not transfer is the assumption that refusing your offer automatically exposes the other side to your costs. In Ontario that is a real possibility under Rule 18. In most US states it is not a feature of family law at all.
Verification note — Ontario. The text of Rule 18 itself could not be read directly: Ontario's e-Laws site requires JavaScript and CanLII blocks automated access. Everything stated above is taken from two accessible official sources — Steps to Justice, Ontario's public legal information service, and the Ontario Court of Justice's own published guide for self-represented litigants. On the question of a form: Steps to Justice states that no specific form is mandated, and the Court's own trial guide refers only to the offer being signed by the party and their lawyer, not to a numbered form. Some practitioner sources refer to a "Form 18". We have therefore not stated a form number. Confirm with your lawyer or on e-Laws before relying on any of this.
Verification note — provinces other than Ontario. We have deliberately not set out the rule numbers, forms or deadlines for British Columbia, Alberta, or any other province. Our research identified plausible provisions but could not verify them against primary sources, and a wrong rule number on a page like this is worse than no rule number. Ask your lawyer what the formal offer mechanism is in your province and what it requires.
Verification note — US states. This is the most significant gap in this guide, and we want to be explicit about it. Our research did not find a source that directly and authoritatively states that state offer-of-settlement rules exclude family law proceedings. The proposition is consistent with how those rules are framed — Florida's, for example, is tied by statute to a "civil action for damages", which a dissolution is not — but we did not verify the exclusion itself. If you are in the United States, ask your lawyer whether your state has any offer mechanism that applies to a divorce. Do not assume from this page that it does not.
Verification note. The statutory citations in the preceding paragraph were not independently verified for this guide. They are included as signposts for a conversation with your lawyer, not as statements of law.
Verification note. We could not verify the current English position on costs and failure to negotiate openly. It is included here for context only. Anyone dealing with an English matter should take English advice.
That is a strategic decision for your lawyer, and it depends on where you are, what stage the matter is at, and how confident you are in the outcome. A formal offer is a commitment — it can be accepted, and you have to be content to be bound by it.
In Ontario, the court may order them to pay part of your legal fees. "May" is doing work in that sentence — it is discretionary, and it applies in relation to motions and trials rather than conferences. Elsewhere, the answer depends entirely on your jurisdiction.
Generally yes, subject to the rules that apply, and until it has been accepted. The mechanics matter and vary, so do it through your lawyer rather than by sending an email.
No. A without prejudice letter is ordinary settlement correspondence, protected in ways that differ between Canada and the US. A formal offer is a specific instrument made under a court rule, with specific consequences. Some offers are both. They are not interchangeable, and treating them as such is a common and expensive error.
Asking is reasonable. "Is a formal offer to settle something we should be considering at this stage?" is a fair question and takes a minute to answer. There may be good reasons not to — timing, incomplete disclosure, or that the mechanism does not apply where you are.
Last reviewed August 2026. Researched and written by Neta, founder of SortMyDivorce. I am not a lawyer and this is not legal advice — laws, fees and forms change, so please confirm current details with the official sources above or a local family lawyer.
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