Can a separation agreement be changed later?

Yes. Agreements can be varied by mutual consent at any time. Courts can also vary child support and spousal support if there has been a material change in circumstances. Property division is generally final once agreed.

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Separation Agreement

Separation Agreements in Ontario

Q: Can child support be waived in a separation agreement?

No. Both parents have a legal obligation to support their children. No separation agreement can eliminate this obligation. Child support below the Federal Guidelines amount is not binding.

Governing legislation: Family Law Act, R.S.O. 1990, Children's Law Reform Act

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Property Division

Equalization of Net Family Property (NFP). Each spouse calculates their NFP (assets minus debts at date of separation, minus assets brought into marriage). The spouse with the higher NFP pays the other half the difference.

What can be excluded

Excluded property: gifts and inheritances received during the marriage, personal injury damages, insurance proceeds (not for loss of income), property owned before marriage (less debts). The matrimonial home is treated differently — it has no exclusion regardless of when acquired.

Spouses can contract out of the equalization regime via a valid separation agreement.

Spousal Support

Length of marriage, roles during marriage (career sacrifice, childcare), economic disadvantage, ability to become self-sufficient. Courts use the Spousal Support Advisory Guidelines (SSAGs) — these are guidelines, not legislation.

Duration: Roughly 0.5–1 year of support per year of marriage for marriages under 20 years. Indefinite support possible for long marriages or where spouse cannot become self-sufficient.

Spousal support can be waived by agreement if both parties consent with legal advice.

The federal Spousal Support Advisory Guidelines (SSAGs) are used as a reference across Canada for calculating support amounts and duration. They are not legislation — but courts and lawyers treat them as a strong starting point.

Child Support

Child support cannot be waived

Both parents have a legal obligation to support their children. No separation agreement can eliminate this obligation. An agreement that sets child support below the Federal Guidelines amount is not binding.

Federal Child Support Guidelines apply. Amount based on payor's income and number of children. Both parents have a legal obligation — cannot be waived. Special expenses (childcare, medical, extracurricular) are shared in proportion to income.

→ Calculate child support using the federal online tool

Parenting Arrangements

Terminology in Ontario

Since 2021 under the federal Divorce Act: "decision-making responsibility" (formerly custody) and "parenting time" (formerly access). Ontario courts use both sets of terms depending on whether divorce is involved.

The child's best interests are paramount. Both parents typically retain decision-making responsibility for major decisions (education, health, religion) unless one is clearly unsuitable.

Signing Requirements

Witnesses

Each spouse's signature must be witnessed by a separate witness. The witness must be present when the spouse signs. Witnesses cannot be the other spouse.

Independent Legal Advice

Strongly recommended. Courts may set aside agreements made without ILA if a party claims they did not understand what they were signing. An ILA certificate is not legally required in Ontario but greatly strengthens enforceability.

Court Filing

A separation agreement does not need to be filed with the court to be valid in Ontario. However, if you want to enforce child support through the Family Responsibility Office (FRO), the agreement must be filed with the court.

Steps to Complete Your Agreement

1
Prepare a complete list of all assets and debts (Financial Disclosure).
2
Exchange financial disclosure with your spouse — both parties must have full information.
3
Agree on division of property, support, parenting, and any other issues.
4
Draft the agreement (ideally with lawyers, or with a template and then ILA review).
5
Each party signs the agreement before a witness.
6
Each party should ideally have their own lawyer review the agreement before signing (ILA).
7
Keep signed copies. File with court only if you want FRO enforcement of child support.

Critical points for Ontario

!Child support cannot be waived or set below the Federal Guidelines amount.
!A matrimonial home requires special treatment — see a lawyer if the home is involved.
!Agreements signed under duress, without disclosure, or without understanding can be set aside by courts.
!This template is a starting point — a family lawyer should review before you sign.
!Pension division requires separate steps: Pension assets are NOT automatically split by a separation agreement. Each pension plan (employer, OMERS, HOOPP, federal public service, etc.) has specific forms and procedures. A domestic contract must specifically address pensions and each plan administrator must receive the appropriate documentation. Consult a family lawyer about pension rollover (T2220 form for RRSPs/pension plans).

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Official sources

Last updated: June 2026

Guidepost is not a law firm. Family law is complex and fact-specific — this guide is for general informational purposes only and is not legal advice. Consult a family lawyer before signing any separation agreement. Full disclaimer.