The Spousal Support Advisory Guidelines are one of the most important — and most misunderstood — tools in Canadian family law. Developed by Professors Carol Rogerson (University of Toronto) and Rollie Thompson (Dalhousie University) with Department of Justice funding, the SSAG were finalized in July 2008 and have since become the de facto framework for spousal support calculations across Canada.

But the SSAG are advisory, not law. They don't determine whether a spouse is entitled to support — that's a threshold legal question. What they do is provide ranges for the amount and duration of support once entitlement is established.

For practitioners, understanding exactly how those ranges are calculated is essential. Here's a practical walkthrough of both formulas.

The Without-Child Support Formula

This formula applies when there are no dependent children — either because the marriage didn't produce children or because the children are now independent.

It's the simpler of the two formulas, and it's based on two variables: the difference in the spouses' gross incomes and the length of the marriage.

Amount range

The formula generates a range from 1.5% to 2.0% of the difference in the spouses' gross incomes, multiplied by the number of years of marriage (or cohabitation). The percentage is capped at 50% — meaning that even in a very long marriage, the amount will not exceed half the income difference.

Duration range

Duration runs from 0.5 to 1.0 years of support for each year of marriage.

The Rule of 65

If the years of marriage plus the age of the support recipient at separation equals or exceeds 65, the SSAG suggest that support may be indefinite (no fixed end date). This reflects the reality that older recipients from long marriages face significant barriers to achieving economic self-sufficiency.

Worked Example: Without-Child Formula

Facts: Anna and David are divorcing after 15 years of marriage. No dependent children. Anna earns $110,000/year gross. David earns $45,000/year gross. David is 52 at separation.

Step 1 — Income difference: $110,000 − $45,000 = $65,000

Step 2 — Amount range:

Low: 1.5% × $65,000 × 15 years = $14,625/year ($1,219/month)
High: 2.0% × $65,000 × 15 years = $19,500/year ($1,625/month)

Check the cap: 2.0% × 15 = 30%, which is under the 50% cap. No adjustment needed.

Step 3 — Duration range:

Low: 0.5 × 15 = 7.5 years
High: 1.0 × 15 = 15 years

Step 4 — Rule of 65 check:David's age (52) + years of marriage (15) = 67. This exceeds 65, so the SSAG suggest indefinite duration may be appropriate.

Result: $1,219–$1,625/month, with indefinite duration indicated by the Rule of 65.

Where the amount falls within the range depends on factors like the basis for entitlement (compensatory vs. non-compensatory), the recipient's prospects for self-sufficiency, and the standard of living during the marriage. These are judgment calls for the lawyer and ultimately the court — the formula gives the range, not the answer.

The With-Child Support Formula

This is where things get considerably more complex. When child support is also being paid, the SSAG use a different methodology based on Individual Net Disposable Income (INDI).

The core concept: after accounting for child support, taxes, and mandatory deductions, the with-child formula aims to leave the recipient spouse with 40% to 46% of the combined INDI of both spouses.

Why it's more complex

Child support is calculated first (using the Federal Child Support Guidelines tables). That child support payment affects both spouses' tax positions — it's not taxable to the recipient or deductible by the payor. But spousal support IS taxable to the recipient and deductible by the payor. This creates a feedback loop: the amount of spousal support changes the tax calculations, which changes the net disposable income, which changes the spousal support range.

The with-child formula requires iterative calculation to converge on the correct range.

Worked Example: With-Child Formula

Facts: Sarah earns $85,000/year. Michael earns $62,000/year. Two children (ages 8 and 11). Sole custody with Sarah. Ontario.

Step 1 — Child support:Using the Federal Child Support Guidelines table for Ontario, Michael's child support obligation for 2 children at $62,000 income is $913/month ($10,956/year).

Step 2 — Calculate INDI for each spouse: This requires computing after-tax income for each spouse, subtracting child support paid (for the payor) and adding child support received (for the recipient), and accounting for government benefits like the Canada Child Benefit.

Sarah's INDI (after receiving child support, after taxes): ~$65,800
Michael's INDI (after paying child support, after taxes): ~$40,200
Combined INDI: ~$106,000

Step 3 — Apply the 40–46% range:

Low end (40%): Sarah should have $42,400 of combined INDI → Spousal support needed: ~$274/month
High end (46%): Sarah should have $48,760 of combined INDI → Spousal support needed: ~$696/month

Step 4 — Duration: Marriage-based: 6 to 12 years. Child-based: youngest child is 8, up to 10 more years. Longer result applies: 6 to 12 years.

Result: $274–$696/month for 6–12 years.

Where Practitioners Need to Exercise Judgment

The SSAG give you a range. Placing a recommendation within that range — or arguing for a departure from it — is where legal expertise matters.

Key factors that influence positioning within the range include the nature of entitlement (compensatory support for career sacrifices carries different weight than non-compensatory support based on need), the recipient's realistic prospects for economic self-sufficiency, the standard of living during the marriage, and the payor's ability to pay after their own reasonable expenses.

Why Software Matters

Manual SSAG calculations are error-prone, particularly with the with-child formula. The iterative tax calculations, the interaction between child support and spousal support, the provincial tax variations — these create multiple opportunities for arithmetic errors that can significantly affect the ranges presented to clients and courts.

The right software doesn't replace judgment. It ensures the arithmetic is correct so the lawyer can focus on the judgment calls that actually require their expertise.

Divorce Copilot calculates both SSAG formulas with full tax modeling, iterative convergence for the with-child formula, and plain-language explanations of every result. Try it free for 14 days →

Understanding SSAG Calculations: A Practical Guide for Family Lawyers