Retroactive claims: up to 10 years
A DTC approval can reach backwards. If a person was eligible in earlier years but never claimed the disability amount, the CRA may reassess those returns for up to 10 years. This is where the largest single reassessments come from, because several years of unused credits can be claimed at once. It is also where the most expensive mistakes happen, because each past year must be claimed at that year's amount and rate, and because a transfer to a family member must be handled year by year.
How past years are adjusted
The easiest route is the box in Part A of Form T2201 asking the CRA to adjust past returns automatically. If that box was ticked and the certificate is approved for earlier years, the CRA will reassess those returns itself. If it was not ticked, past years can still be adjusted, either through "Change my return" in CRA My Account for each year, or by writing to the CRA to ask for an adjustment. Either way, the practitioner must have certified that the impairment met the test in each year claimed; approval for the current year alone does not automatically prove eligibility ten years ago.
Federal disability amounts, past 10 years
| Tax year | Disability amount | Supplement, under 18 |
|---|---|---|
| 2025 | $10,138 | $5,914 |
| 2024 | $9,872 | $5,758 |
| 2023 | $9,428 | $5,500 |
| 2022 | $8,870 | $5,174 |
| 2021 | $8,662 | $5,053 |
| 2020 | $8,576 | $5,003 |
| 2019 | $8,416 | $4,909 |
| 2018 | $8,235 | $4,804 |
| 2017 | $8,113 | $4,733 |
| 2016 | $8,001 | $4,667 |
These are the amounts published on the CRA's claiming page. Each year's credit value depends on that year's lowest federal rate and on the tax payable in that year, and the supplement reduction rules for a child must be applied year by year as well. Provincial and territorial amounts for past years are separate and must be claimed on the provincial or territorial forms for those years.
Illustrative multi-year sum (assumptions stated)
Example — three years of base amounts. Assumptions: adult approved for 2023, 2024, and 2025, who never claimed the DTC in any of those years. The base amounts add up as $9,428 + $9,872 + $10,138 = $29,438. That $29,438 is a sum of disability amounts, not a refund and not a credit total. The actual tax effect in each year is that year's amount multiplied by that year's lowest federal rate, limited by that year's tax payable, with any unused part transferable only if a supporting family member is identified for that year. Anyone who quotes a multi-year refund without working through those year-by-year limits is guessing.
Sources: Canada Revenue Agency, "Claiming the DTC" page on canada.ca (10-year rule, past-year amounts table, automatic reassessment).
Photo credits: dt19.jpg — k; dt20.jpg — k; dt21.jpg — k