Late Tax Filers: How to Settle Back Taxes Before Year-End

The last day tax preparers can electronically file clients’ returns for tax years 2017 through 2024 — and submit amended T1 returns for 2021 through 2024 via ReFILE — before an annual pause is January 30, 2026. If you’re behind on filing, there are important reasons to make tax preparation a priority over the holidays and get any missed returns in well before December 31.

The legal backdrop. Under the Income Tax Act, the ordinary reassessment window is three years from the date a notice of assessment or reassessment is mailed or received. However, under the taxpayer relief provisions, individuals can sometimes request adjustments for errors or omissions going back up to 10 years for personal returns. This extended window can preserve tax refunds, contribution room and other benefits — but only if you act before the statute-barrier date.

Why tax year 2015 matters. Tax year 2015 will become statute-barred under the 10-year taxpayer relief rules after December 31, 2025. Once that window closes, you lose the ability to claim many benefits and corrections for 2015. These include:

1. Any tax refunds owed for the 2015 tax year.
2. The chance to create RRSP contribution room for 2015, which can affect retirement savings capacity later.
3. Carried-forward deductions and non-refundable credits tied to 2015, such as moving expenses, medical expenses, charitable donations and political contributions.
4. Refundable credits you might be entitled to, including the Canada Child Benefit, the GST/HST credit, the Canada Workers Benefit and the refundable medical expense supplement.
5. Unreported capital and non-capital losses that could offset income in 2015 or carry forward to reduce future tax — once lost, these losses can increase tax bills in later years.
6. The opportunity to claim the lifetime capital gains exemption for dispositions that occurred in 2015.
7. Alternative Minimum Tax (AMT) carry-forwards from prior years that could otherwise be applied against 2015 income.

Spousal filing issues. If one spouse fails to file, household income may be under-reported for income-tested benefits and credits. If the spouse who filed on time estimated the missing spouse’s income incorrectly, benefits already received could be clawed back in a CRA audit or taxes could increase. In some situations — for example, when property transfers or joint financial transactions are involved — spouses can also be held jointly liable for tax debts.

Provincial rules differ. Not every federal T1 provision qualifies for the 10-year taxpayer relief period. For many provincial adjustments, only the standard three-year reassessment period applies, and in Quebec that period is four years. That means provincial credits or deductions tied to provincial law may become unavailable much sooner than federal 10-year relief would suggest.

Pension income-splitting elections. Some tax-reduction elections have shorter filing windows. For example, joint elections to split pension income using Form T1032 are typically allowed only within three calendar years after the filing due date. That means these elections must be made within a narrow window or the opportunity is lost. Be sure to check the specific timing rules for any election you intend to use to reduce tax.

Social benefits and missed claims. Certain social benefits have short look-back periods. For example, missed Old Age Security (OAS) benefits are generally claimable for up to 11 months after the entitlement arose, unless a severe incapacity prevented applying earlier. Because OAS is income-tested, filing tax returns is essential to establish eligibility and limit clawbacks based on net income.

Newer programs also have defined retroactive windows. The Canada Dental Care Plan (CDCP) allows reconsideration of entitlement for up to 24 months after the benefit period ends, though the government can recover overpayments up to six years if false or misleading information was provided. The Canada Disability Benefit (CDB), effective since July 2025, permits retroactive payments for eligible months up to 24 months prior to an approved application; again, overpayments may be recoverable by the government for up to six years.

Why late filing can be costly. Filing on time avoids lost benefits and helps prevent escalating penalties and interest. Late or missing returns can trigger a range of costly consequences when taxes are owing, including:

• Gross negligence penalties. The CRA can impose a civil penalty if it determines a taxpayer deliberately avoided filing or ignored obligations. Such penalties can amount to 50% of the tax owing, and interest compounds on top of that at prescribed rates.
• Penalties for deceit or evasion. Where intentional deception is found, penalties can be severe: in extreme cases, amounts equal to 200% of the taxes owing plus interest and civil penalties may apply, and criminal sanctions are possible.
• Criminal fraud consequences. Under the Criminal Code, serious tax fraud convictions can carry lengthy prison sentences and other long-term consequences such as fingerprinting and travel restrictions.

If you believe you owe taxes, first have a tax professional verify whether the CRA’s assessment is accurate — mistakes do happen — then pay or arrange payment promptly to minimize penalties and interest.

Bottom line

Filing returns is the gateway to claiming credits, refunds and other tax preferences. If you have missed years to file, plan now to catch up before statutory windows close. File outstanding returns or request adjustments for errors and omissions while you still can — acting before the relevant deadlines may preserve refunds, contribution room and social benefits you would otherwise lose.

Further reading about minimizing taxes:

• A wish list for Carney’s fall budget
• How the Canada GST/HST tax credit works
• Tax implications of giving your spouse money to invest
• How to set up CRA direct deposit