Changing a Family Law Agreement in Ontario

Why Agreement Terms Change Over Time

A separation agreement is written to fit the circumstances that existed when it was signed. Years later, those circumstances can look very different — incomes rise or fall, children grow older and their needs change, someone relocates, or a new relationship begins. It is common, and entirely normal, for spouses to want to revisit part of an agreement they signed some time ago.

This page is about ordinary, forward-looking changes to an agreement whose terms both people generally still accept as validly made. It is not about arguing that the agreement was legally flawed from the start — that is a different topic, covered separately under challenging a separation agreement.

Can You Just Change an Agreement by Mutual Consent?

Generally, yes. A separation agreement is a type of domestic contract under Ontario's Family Law Act, and like most contracts, the people who made it are generally free to change it later, at any time, as long as they both agree to the new terms. You do not need a judge's permission to change an agreement by mutual consent, and you do not need to go back to court to do it.

A change can be made through a short amending agreement that modifies only the specific terms you want to update, or through an entirely new agreement that replaces the old one. Either approach is generally acceptable, though a full replacement agreement can be clearer where several terms are changing at once, or where the original document has already been through more than one earlier amendment.

Formalizing a Change: Writing, Signatures & Witnesses

An amendment to a separation agreement is still a domestic contract, so it is generally expected to meet the same formal requirements as the original document. In general terms, that means the change should be:

• Made in writing
• Signed by both parties
• Witnessed

A verbal understanding to change a term, even one both people genuinely intend to honour, does not meet this standard and is generally unenforceable if a dispute arises later. The same is true of an informal exchange of text messages or emails discussing a change — it may reflect what you both intended, but it is a poor substitute for a properly signed and witnessed document if the other person later denies agreeing, or changes their mind.

As with the original agreement, independent legal advice is not mandatory for an amendment, but it is widely recommended. Read more about independent legal advice and why it matters.

Parenting Terms: Easiest to Revisit

Parenting terms in a separation agreement — covering decision-making responsibility and parenting time — are generally the most straightforward to revisit, and not only because parents change their minds as children grow. Under Ontario and federal family law, parenting terms in any agreement remain subject to a court's ongoing oversight based on the best interests of the child.

In practice, this cuts two ways. If both parents agree that a parenting arrangement needs to change, they can generally update it by mutual consent, the same as any other term. And because a court can, in principle, override even long-standing parenting terms if it finds they no longer serve a child's best interests, parenting arrangements are treated as less permanently "locked in" than property terms, even when both parents originally agreed to them in a properly signed agreement.

Support Terms: Sometimes Variable

Child support and spousal support terms sit between parenting and property in how easily they can change. Spouses can always update support terms by mutual consent. Where one side does not agree, support terms may still be variable in some circumstances — particularly where the agreement itself contemplates a future review (for example, a clause requiring the parties to revisit support after a set number of years or a specific event), or where there has been a material change in circumstances since the agreement was signed, such as a significant change in income or the needs of a child.

Because the process and legal test for changing support can differ depending on your situation, see changing child or spousal support for a fuller discussion of when a variation may be available and how it is generally pursued.

Property Terms: Generally More Final

Property terms — how spouses divided assets, debts, and the matrimonial home — are treated differently from parenting or support terms. Once a separation agreement dividing property has been validly made, its property terms are generally considered final and binding, much like the resolution of a claim in any other type of contract.

This means mutual consent still works — both spouses can always agree to redivide property or adjust a term later if they both want to. But if one spouse simply changes their mind about a property division they already agreed to, a court will not generally reopen it just because circumstances changed or the deal no longer feels fair in hindsight. Unwinding a property term against the other spouse's wishes generally requires a successful legal challenge to the validity of the agreement itself — for example, on the basis of non-disclosure — rather than an ordinary request for a variation. See challenging a separation agreement for what that process generally involves.

When You Can't Agree: Going to Court

If mutual consent is not possible, a court can sometimes change certain terms even over one spouse's objection, though how readily it will do so depends heavily on which type of term is at issue, for the reasons described above. This is generally pursued through a motion to change, a court process available where a spouse wants to update an existing agreement or order without both parties agreeing.

Broadly speaking, courts tend to be most willing to intervene on parenting terms where the child's best interests require it, will vary support terms where a material change in circumstances or an agreed review is shown, and are generally most reluctant to interfere with property terms outside of a successful challenge to the agreement's validity. If you expect to need court involvement, read more about changing a family court order, since a similar motion-to-change process is often used whether the original terms come from an agreement or an order.

Changing vs. Challenging an Agreement

It is worth being precise about the difference between these two ideas, since people sometimes use "changing" and "challenging" loosely to mean the same thing.

• Changing an agreement means updating its terms going forward, generally because circumstances have shifted since it was signed. It does not require arguing anything was wrong with the agreement when it was made — both people can simply agree the old terms no longer fit and sign something new.
• Challenging an agreement (sometimes called setting it aside) means arguing the agreement, or a specific provision in it, should not be enforced at all because of a legal defect from the outset — for example, one spouse failed to disclose significant assets or debts, or was pressured into signing. See challenging a separation agreement for how that different process generally works.

Property terms are a useful illustration of why the distinction matters: they are generally too final to "just change" if the other spouse disagrees, so the only realistic route to undoing one against their wishes is usually a successful challenge, not an ordinary request for a variation.

Keeping Records of Any Changes

Whenever an agreement is amended, keep clear records of exactly what changed and when. This generally includes the signed and witnessed amending document itself, any financial disclosure exchanged in connection with the change, and, where support terms were updated and previously filed with a court, confirmation of whether the updated version also needs to be filed to replace what was filed before.

Good records matter because an agreement that has been amended more than once can become difficult to interpret if the amendments are not kept together with the original. Store the complete history — original agreement plus every amendment — somewhere both spouses can access if a question arises later.

Frequently Asked Questions