When a marriage or common-law relationship ends in Ontario, a separation agreement is the most common method for resolving the legal consequences — division of property, spousal support, child support, and parenting arrangements — outside of court. A separation agreement is a type of "domestic contract" governed by Part IV of Ontario's Family Law Act, RSO 1990, c F.3 (FLA). Getting the agreement right is critical: a poorly drafted or procedurally defective agreement can be challenged and set aside by the court, undoing years of negotiation and creating significant legal uncertainty.

What Must Be in Writing: FLA Section 54

Section 54 of the FLA provides that a domestic contract (including a separation agreement) must be:

  1. In writing.
  2. Signed by both parties.
  3. Witnessed by at least one person (for each party's signature).

A verbal separation agreement is not legally binding in Ontario, no matter what was said or agreed upon. All the terms that the parties want to be legally enforceable must be in the written document. This is a firm rule — courts will not "imply" terms into a separation agreement or enforce verbal understandings that are not reflected in writing.

The agreement should address the key subject matters that the parties are resolving:

Independent Legal Advice: The ILA Requirement

While independent legal advice (ILA) is not technically required by the FLA to make a separation agreement valid, it is critically important to the agreement's enforceability. Section 56(4) of the FLA allows a court to set aside a domestic contract (or a provision in one) if a party did not have ILA at the time of signing, particularly where the absence of legal advice contributed to the party entering into an unfair agreement.

In practice, almost every Ontario family lawyer requires their client to obtain ILA before signing a separation agreement — and provides a certificate of ILA confirming that legal advice was given. The standard practice is:

Why ILA Matters for Both Parties: The party who benefits more from a separation agreement has as much to gain from the other party obtaining ILA as the disadvantaged party does. If the disadvantaged party later challenges the agreement on the basis they lacked ILA and didn't understand what they were signing, and succeeds, the entire agreement can be unwound — regardless of whether it was fair. Insisting on ILA protects both parties.

Section 56: Grounds for Setting Aside

Section 56(4) of the FLA authorizes a court to set aside a domestic contract or any provision in it if:

The most commonly litigated ground is non-disclosure of financial information. Ontario courts have consistently held that parties to a separation agreement must make full, frank, and voluntary financial disclosure before signing. Each party should provide (and receive) a complete financial statement disclosing all assets, liabilities, income, and expenses. Hiding assets — even accidentally — can be grounds to set aside the agreement years later.

Full Financial Disclosure Is Non-Negotiable: Signing a separation agreement without exchanging complete financial disclosure is one of the most common and costly mistakes in family law. If the agreement is later challenged, and a party can show they were not aware of the other's significant asset or income, the court has broad discretion to set aside the entire agreement or specific provisions. Complete and documented financial disclosure protects both parties.

Negotiating With and Without Lawyers

Parties can negotiate a separation agreement in several ways:

Separation Agreement vs. Court Order

A separation agreement is a contract between the parties. A court order is issued by a judge and can be enforced differently. Key differences:

Corollary Relief in Divorce Proceedings

When a couple proceeds with a divorce under the federal Divorce Act, the court can grant "corollary relief" — orders for child support, spousal support, and parenting arrangements as part of the divorce proceeding. If the parties have a comprehensive separation agreement, they can ask the court to incorporate it into the divorce order. If they cannot agree on corollary relief, the court will impose its own order, which may or may not reflect what the parties expected.