Prenups and Separation Agreements in Canada: What the Law Actually Says

A prenuptial agreement and a separation agreement are the two contracts that govern money and property in a relationship — one signed at the start, one at the end. In Canada, both are domestic contracts, and the law treats them with unusual seriousness: get the formalities wrong, and a court can throw the entire agreement out.

In Ontario, a prenup is legally called a marriage contract (common-law couples use a cohabitation agreement instead). Under section 55(1) of the Family Law Act, it is unenforceable unless it is in writing, signed by both parties, and witnessed. That is only the starting line. Under section 56(4), a court can set aside a marriage contract if one party hid significant assets or debts, did not understand what they were signing, or the terms are unconscionable. That is why full, honest financial disclosure and independent legal advice — each party with their own lawyer — are the real foundation of an enforceable prenup. And timing matters: sign it well before the wedding, not the week of, so nobody can later claim they signed under pressure.

A separation agreement settles the end of the relationship without going to court: parenting arrangements, child and spousal support, and the division of property and debts. In Ontario it is a domestic contract under the Family Law Act, enforceable when it is in writing, signed by both of you, and witnessed. The same protections decide whether it holds up: full financial disclosure on both sides, no pressure or coercion, and independent legal advice for each of you. Two cautions worth knowing: child support should follow the Federal Child Support Guidelines, and courts can always vary parenting and child-support terms later if a child's best interests require it — those parts are never truly final.

Both documents share one hard rule: a handshake or verbal promise has no legal force in family law. Only the written, signed, witnessed document counts.

What should these agreements actually cover? A prenup typically addresses how property brought into the marriage is treated, how assets acquired together will be divided, whether spousal support will be paid and how much, and how debts are handled — it cannot decide child custody or child support in advance, since courts decide those on the child's best interests at the time. A separation agreement is more detailed still: it should spell out parenting time and decision-making responsibility, the exact support amounts and payment dates, who keeps the matrimonial home and how a buyout is funded, how pensions and RRSPs are divided, and who pays which debts. Vague language is the enemy — 'we will share expenses fairly' means nothing in a dispute; dollar amounts, dates, and account numbers mean everything.

A properly drafted agreement at the start — or a fairly negotiated one at the end — is far cheaper than litigating the difference years later.

Our free prenuptial agreement generator and our free separation agreement generator walk you through the key terms province by province, so nothing important gets missed. For high-value assets, a business, or anything contested, have a lawyer review the final document before you sign — independent advice is the single strongest protection against a future challenge.