How far back can CRA relief cover if I want interest cancelled on an old tax debt?

Taxpayer relief for interest can generally reach back 10 years, measured from the year you make the relief request, but the important nuance is what that 10-year window actually looks at. It's based on when the interest itself accrued, not simply when the original tax debt first arose, which means interest relief can potentially extend to older debts than people often assume, provided the interest in question accrued within that relevant 10-year window.

This distinction matters because a tax debt itself might be considerably older than 10 years, while interest continuing to accrue on that debt more recently can still fall within the relief window even though the underlying debt predates it. People often assume relief is limited strictly by how old the original debt is, when the actual test looks at the timing of the interest accrual instead - a more favourable framing for someone dealing with an old debt that's still generating interest. Because this reach-back principle and its interaction with an old debt's history can be genuinely confusing, working through exactly which interest charges fall within the relevant window is worth doing carefully, ideally with someone who can confirm the current rules, before assuming either that relief is or isn't available for your specific situation.