Updating a Prenup or Cohabitation Agreement After Marriage, Kids or a Move

Many couples sign a cohabitation agreement before moving in or a marriage agreement before the wedding, file it away and never look at it again. Then life changes: you marry, have children, buy a home, receive an inheritance or start a business.

BC law lets spouses change their agreement at any time, but an amendment that is poorly drafted or signed without proper disclosure can create new problems. This guide explains how updating works and what a court looks at if an older agreement is ever challenged.

Why an older agreement may no longer fit

If you are still deciding whether to sign an agreement at all, start with our guides to marriage agreements and cohabitation agreements. This article is for couples who already have one and whose circumstances have moved on.

An agreement is written for the life you had when you signed it. A cohabitation agreement drafted when you were renting together may say nothing useful about a house you later bought in both names. A marriage agreement signed before children may contain a spousal support waiver that looks very different once one of you has stepped back from work to raise a family. The agreement may still be binding, but the gap between what it says and how you now live is exactly what invites a dispute later.

Can you change a prenup or cohabitation agreement in BC?

Yes, if you both agree. Section 6 of the Family Law Act allows two or more people to make an agreement about a matter that may become a family law dispute in the future, and says an agreement is binding whether or not there is consideration and whether or not a lawyer or other family dispute resolution professional was involved. Section 7 deals directly with changes: when a new agreement changes a previous one, each changed part of the old agreement is treated as revoked and the rest stays in effect.

That rule is helpful, but it means an amending agreement has to be precise about which clauses it replaces. Where the changes are extensive, many couples sign a fresh replacement agreement instead, so there is one complete document rather than an original plus a series of amendments. Neither spouse can change the agreement alone; without both signatures, only a court can set it aside or replace it.

Formalities that make the updated agreement stronger

For property terms, section 93 applies to a written agreement where each spouse's signature is witnessed by at least one other person (the same person can witness both). When an agreement meets that standard, section 94 says the court cannot make its own property division order on matters the agreement covers unless all or part of the agreement is first set aside. Treat any amendment with the same care as the original:

• Put it in writing and have each signature witnessed. A side email or verbal understanding does not give you the same footing.
• Exchange fresh financial disclosure. Failing to disclose significant property, debts or other relevant information when the agreement was made is one of the grounds for setting it aside under section 93(3).
• Give each person time and their own advice. The court can also act if one spouse took improper advantage of the other's vulnerability, including ignorance, need or distress, or if a spouse did not understand the nature or consequences of the agreement. Separate legal advice and no last-minute signing help show neither happened.

How a court looks at an agreement that has aged

Even when nothing was wrong at signing, section 93(5) lets the Supreme Court set aside or replace all or part of a property agreement that is significantly unfair, considering the length of time since it was made, the spouses' intention to achieve certainty, and how far they relied on its terms. The passage of time is itself one of the factors, which is one reason to revisit an agreement after major life events rather than leaving it untouched for decades.

Spousal support terms are tested under section 164, which adds further factors: any changes since the agreement in the condition, means, needs or other circumstances of a spouse, and how well the agreement meets the objectives of spousal support. A support waiver signed before children, a career change or an illness is therefore more exposed than one that was reviewed after those events. If a spouse wants to challenge an agreement, section 198(3) generally allows two years from when the spouse discovered, or reasonably ought to have discovered, the grounds.

Children: what an agreement cannot settle in advance

Couples sometimes include terms about future children in a prenup. Under the Family Law Act, an agreement about parenting arrangements (section 44) or child support (section 148) is binding only if it is made after separation, or when the parties are about to separate, to take effect on separation. Agreements about parenting must also be made in the best interests of the child only (section 37). Clauses written years before a child is born will not decide those questions.

What the arrival of children often does change is the fairness of the property and spousal support terms. If one parent's earnings or career path changed because of child care, that is a good time to review the agreement together.

Common life events that call for a review

• You married after signing a cohabitation agreement. Check whether the agreement says it continues if you marry. If it is silent, get advice on whether it still covers the relationship as it now stands.
• You bought a home. How title is held and who contributed the down payment can interact with the agreement in ways neither of you intended. Our article on owning a home before the relationship explains the baseline rules.
• You received an inheritance or a gift. Inheritances and third-party gifts are generally excluded property under section 85, but section 84(2)(g) treats any increase in the value of excluded property during the relationship as family property. An agreement can deal with that growth expressly.
• You started or sold a business, or one of you retired. Valuation and support assumptions may be out of date.
• You moved to or from another province or country. Different laws may apply where you now live, so have the agreement reviewed where you are settled.

An updated agreement should sit alongside an updated estate plan. When you change the agreement, it is sensible to look at your will and beneficiary designations at the same time; see when to update your will.

Signed an agreement years ago? Have it reviewed before the next big change

Our family lawyers can review your existing marriage or cohabitation agreement, explain how the Family Law Act is likely to treat it today, and prepare an amending or replacement agreement that reflects your current circumstances.

Call 604-259-2844 or send us a message to arrange a consultation at our Vancouver office.