If you forgot to claim medical expenses on a prior year’s return, you can go back and recover the credit: CRA accepts changes up to 10 years back, so there is no time pressure. The parts specific to a missed claim are choosing the 12-month period, deciding whose return carries the claim, and correcting the right line. This page is part of our guide to filing a tax return.
Haven’t filed your current-year return yet? If it’s before the filing deadline and you haven’t submitted your return, there’s no need for an adjustment at all: just add the medical expenses in your tax software before you file. The tax deadline page shows how much time you have. Everything below applies once a return has already been filed.
The Credit in Brief
The medical expense credit is a non-refundable federal credit on eligible expenses above a threshold (the lesser of 3% of your net income or a fixed dollar amount that is indexed each year), plus a provincial credit at each province’s rate. The rates, the current threshold, worked examples and the full list of eligible expenses are on the medical expense tax credit page.
The 12-Month Period Trick
Medical expenses don’t have to be claimed January to December. You can claim any consecutive 12-month period ending in the tax year. This means if you had a large expense in November, you could claim from December of the previous year to November, potentially sweeping in more expenses from the prior year.
This can significantly increase your claim. Running the numbers for several 12-month windows shows which period produces the largest credit.
What Expenses Are Eligible?
Prescription drugs, dental and vision care, licensed practitioners’ fees, medical devices, private health plan premiums and medical travel are among the common eligible expenses; over-the-counter medications, vitamins, gym memberships and elective cosmetic surgery are not. The credit guide has the full table and CRA’s conditions for each.
Claiming for Multiple Family Members
You can claim eligible expenses for your entire household on one person’s return, so it is worth running the calculation both ways:
- Lower-income spouse: Their 3% threshold is smaller, so a greater portion of expenses exceeds it. This usually produces the larger credit.
- Higher-income spouse: If the lower-income spouse has no tax payable, the credit is wasted (it’s non-refundable). In that case, the higher-income spouse may generate more actual tax savings.
Donations can also be pooled on one spouse’s return; the guide to charitable donations you forgot to claim covers that fix and its own carry-forward rules.
How to Fix a Prior Year’s Return
Step 1: Gather receipts
Collect all eligible medical receipts for the year(s) in question. You don’t need to submit them with your adjustment, but CRA may request them in a review. Receipts are kept for at least six years.
Step 2: Identify the optimal 12-month period
Add up expenses by different 12-month windows to find the period where your total expenses most exceed the threshold.
Step 3: Correct line 33099 (or 33199)
Change line 33099 (you and your spouse’s medical expenses) to the corrected amount for the tax year, or line 33199 for other dependants (see below). Receipts don’t go with the request unless CRA asks for them. The three ways to submit the change, and their processing times, are covered in how to change a filed return.
What happens after you submit
CRA may accept the adjustment and issue a revised Notice of Assessment with any refund owing, request supporting receipts (originals are kept for six years), or deny it and explain why. A denial can be disputed if you disagree.
Medical Expenses for Other Dependants
For expenses paid for a parent, grandparent, older child, sibling, or other dependant who relies on you for support, claim on line 33199. The calculation is different: you subtract the dependant’s own net income from the eligible expenses, then apply the $2,834 or 3% threshold.