Often, yes. Ontario law lets a court order child support for a period before the order is made, and lets it change an existing order retroactively when income or circumstances changed and were not reflected. How far back a court goes depends on the facts, including when the paying parent was told support was being sought and whether income was disclosed.
How retroactive child support works in Ontario
"Retroactive" child support means support for a period that has already passed. It comes up in two common situations: no support (or too little) was paid after separation and nobody went to court, or an order or agreement was in place but the paying parent's income rose and the amount was never updated. For the bigger picture, see our child and spousal support page.
The statutes give courts the power to look back:
- New claims under the Family Law Act. Under the Family Law Act, on a support application the court may make an order "requiring that support be paid in respect of any period before the date of the order" (s. 34(1)(f)).
- Changing an existing Family Law Act order. If there has been a change in circumstances within the meaning of the guidelines, or new evidence has become available, the court may vary a child support order "prospectively or retroactively" and may also relieve arrears (s. 37(2.1)).
- Divorce Act orders. A court may vary, rescind or suspend a support order "retroactively or prospectively" (s. 17(1)).
- No limitation period. Ontario's Limitations Act, 2002 says there is no limitation period for a proceeding to obtain support under the Family Law Act (s. 16(1)(c)). That does not mean any period can be claimed: the court still decides how far back is fair.
A retroactive claim usually moves through these steps:
- Work out what should have been paid. Apply the guidelines to each past year, using that year's income; see how child support is calculated.
- Compare with what was actually paid. The difference for each year is the potential shortfall.
- Identify when the paying parent was told. A clear written request for support or for income information is an important date.
- Gather the income evidence. Past tax returns and notices of assessment for every year in question; see yearly income disclosure.
- Try to settle. Many retroactive claims are resolved by agreement, sometimes with the amount paid over time.
- If not, start a claim or a motion to change. In Toronto, a child support claim under the Family Law Act can start in the Ontario Court of Justice; see the Ontario Court of Justice family courts in Toronto.
Looking back, year by year
| Step | What you need | Why it matters |
|---|---|---|
| Separation date and parenting schedule for each year | Calendar, school records, messages | Decides who would have paid and whether shared parenting applied |
| Paying parent's income for each year | Tax returns and notices of assessment | Table amounts depend on each year's income |
| Section 7 expenses each year | Receipts for child care, health, school and activities | These can form part of a retroactive claim |
| What was actually paid | Bank records, e-transfers, receipts | Credits against what was owed |
| Date of first request | The letter, email or court document asking for support or disclosure | Often central to how far back a court looks |
When support was set by an agreement
Many parents set child support in a separation agreement rather than a court order. The same questions about the past arise, with a few differences. Since the yearly disclosure rule for agreements came into force, a person whose income was used to set child support in a domestic contract or other written agreement must share their tax return and notice of assessment every year, no later than 30 days after the agreement's anniversary (Ontario Child Support Guidelines, s. 25.1). That gives the receiving parent a regular chance to check the amount.
If the agreement has not been updated, the receiving parent can ask for a change by agreement or bring a motion to change under rule 15 of the Family Law Rules, which applies to final orders and agreements. Where the paying parent has defaulted on payments required by the contract, the Family Law Act allows the court to determine and order support even though the contract tries to exclude it (s. 33(4)(c)). Filing the agreement with the court under section 35 also allows its support terms to be enforced and varied like an order.
If you are the parent being asked to pay for the past
A retroactive claim can be stressful and expensive, but there are practical steps that help. Start by checking the numbers yourself: gather your tax returns for each year in question, calculate the table amounts, and add up everything you actually paid, with proof. Credit for informal payments depends on records, so bank statements and e-transfer histories matter.
If there were good reasons why support was lower, such as a period of shared parenting, a job loss, or direct payments for the children's expenses, document them. If paying a large sum at once is not possible, propose a realistic schedule; both agreements and orders can spread retroactive amounts over time. And going forward, keep the yearly disclosure current so the issue does not recur.
What changes the answer
- Notice. Raising support clearly, in writing, puts the paying parent on notice. Delay after that can work against the parent claiming.
- Disclosure. The guidelines require yearly income updates after an order or agreement (ss. 24.1 and 25.1) and production on request (s. 25). A parent who hid an income increase is in a different position from one who disclosed it. Failure to disclose can also lead to imputed income; see what counts as income for support.
- The child's age and situation. Support is owed for a "child" under the Family Law Act or the Divorce Act. If the child has since finished school, the court looks at the period when the child qualified; see child support after 18.
- Ability to pay. A large lump sum can be hard to pay. Courts and agreements can spread payments over time.
- Arrears versus retroactive support. Arrears are amounts already owed under an existing order. Retroactive support creates or increases an obligation for the past. The Family Law Act lets a court relieve arrears in some cases (s. 37(2.1)(b)), so a payor whose income fell should act quickly rather than let arrears build; the same variation process is described in changing or ending spousal support.
- Enforcement. Once ordered, retroactive amounts are enforced like any support debt; see what happens if support is not paid.
A worked example
For example, imagine parents who separated in Toronto four years ago. Their two children live with one parent. The other parent paid $600 a month informally and never shared tax information. Last year, the receiving parent emailed asking for income documents and guideline support. The paying parent's notices of assessment, produced later, show incomes of $85,000, $92,000, $101,000 and $108,000 over the four years.
The guideline table amount for two children at each year's income would be calculated and compared with the $600 a month actually paid. The gap is the potential retroactive amount. A court would look at the date of the email request, the lack of disclosure, the children's needs over that period, and the paying parent's circumstances in deciding how far back to go and how payment should be made. A negotiated agreement might set a lump sum or monthly instalments on top of ongoing guideline support. This example is hypothetical; we do not predict how a court would decide a real case.
Common mistakes with past support
- Accepting informal payments without asking for income information. Without disclosure, the recipient cannot know whether the amount is right.
- Waiting years to raise it. Delay can reduce what a court is willing to order for the past.
- Making the request only verbally. A dated written request is the clearest proof of notice.
- Paying cash with no record. Payors should keep proof of every payment so they get credit for it.
- Ignoring an income increase. Under an order or agreement, the yearly update is mandatory unless the parties opted out of it.
- Letting a temporary arrangement drift. Put support in a written agreement or order early; see support before the case is decided.
What to do this week
- Write down the separation date and, year by year, where the children lived and what support was paid.
- Gather proof of payments: bank statements, e-transfer records, cheques.
- Send a dated written request for the other parent's income documents for the last three years.
- Collect receipts for past section 7 expenses such as child care or orthodontics.
- Use the official federal look-up for each year to estimate the table amount.
- Book a free consultation with us to assess how far back a claim is likely to reach and the best way to raise it.
Frequently asked questions
Is there a deadline to claim past child support?
There is no limitation period for a Family Law Act support claim (Limitations Act, 2002, s. 16(1)(c)). But delay matters to how far back a court looks, so acting promptly is wise.
Can I claim support for a child who is now an adult?
Possibly, for the period when the child qualified for support. The longer ago that was, the harder the claim becomes.
Can a paying parent ask to reduce support retroactively?
Yes. The same powers allow a retroactive decrease, for example after a job loss that was promptly disclosed. Arrears under the old order may be reduced only by a court or an agreement.
Does the Family Responsibility Office collect retroactive amounts?
Once a court orders them, or they are in an agreement filed with the court, they are enforced as support, generally through the Family Responsibility Office.
Will interest be added?
Interest can arise on support debts in some situations, and the Family Law Act lets a court relieve interest on arrears (s. 37(2.1)(b)). Ask about it specifically in your case.
Does the same apply to special expenses?
Past section 7 expenses can be part of a retroactive claim if they meet the guidelines' tests; see special or extraordinary expenses.