With HISA and GIC rates staying elevated over the past two years, a lot of Canadians have meaningful T5 slips they did not have before — and some slipped through unfiled. This is one of the most common and most reliably caught errors the CRA sees, because banks and brokerages submit T5 data directly. Here is what to do.
Why the CRA will almost certainly catch this
When your bank issues a T5 slip for interest earned in your savings account, GIC, or non-registered brokerage account, they do two things: send a copy to you and send a copy to the CRA. The same applies to T3 slips from mutual funds and ETFs.
Every spring, the CRA’s auto-matching system compares the slips on file to what was reported on each return. If a T5 showing $800 in interest was submitted by your bank but your return shows zero investment income, the system flags it automatically. You will receive a Notice of Reassessment adding the income and charging interest — usually within 12–18 months of filing.
Filing a T1 Adjustment proactively is faster, avoids any civil penalty risk, and puts you in control of the timeline.
Step 1: Find out what the CRA already has
Before filing an amendment, check what slips are on file.
- Log in to CRA My Account
- Under Tax Information Slips, select the relevant tax year
- Review all T5, T3, and T5008 slips on file
You can also open your bank and brokerage accounts directly and download your year-end tax documents, usually available from mid-January to the end of March each year.
Note: If your interest was under $50 from a given institution, they may not have issued a slip — but you still owe tax on it. Check your statements for any interest credited during the year.
Step 2: Identify which income type applies
Different investment income is reported on different lines of your T1 return:
| Income type | Where it goes | Common sources |
|---|---|---|
| Interest income | Line 12100 | Savings accounts, GICs, term deposits, bonds |
| Eligible dividends (Canadian) | Line 12000 | Canadian stocks, eligible dividend ETFs |
| Other than eligible dividends | Line 12010 | Private corporation dividends |
| Foreign investment income | Line 12100 | US or international interest/dividends |
| Capital gains | Schedule 3 | Sale of investments, ETFs, stocks |
The T5 slip covers interest and dividends. The T3 slip covers income from trusts, mutual funds, and ETFs.
Step 3: File a T1 Adjustment
Via CRA My Account (fastest — ~2 weeks)
- Log in and select Change My Return
- Choose the tax year with the missing income
- Update Line 12100 (or whichever line applies) with the correct total
- Add a brief note: “Adding T5 interest income not included in original filing”
- Submit
The CRA will reassess, add the tax owing, and charge prescribed interest from April 30 of the year it was due. No civil penalty applies for proactive disclosure.
Via tax software (2–3 weeks)
Open your saved return, add the T5 income, and re-NETFILE the amendment. Most certified software supports prior-year amendments.
Via mail — T1-ADJ form (6–8 weeks)
Download and complete the T1-ADJ form, attach a copy of the T5 slip, and mail to your CRA tax centre.
How much extra tax will you owe?
The additional tax depends on your marginal rate. Interest income is fully taxable at your marginal rate — it is treated the same as employment income.
Example: You forgot to report $1,200 in HISA interest. Your marginal rate is 33.5% (Ontario, ~$75K income).
- Additional federal + provincial tax: ~$402
- CRA prescribed interest (currently 8% annually) on $402 from April 30 → roughly $32 per year elapsed
- Total owed if you self-correct after 1 year: ~$434
- No civil penalty because you corrected it proactively
If the CRA finds it first and decides to apply gross negligence penalties, the penalty alone can be 50% of the understated tax — making proactive correction dramatically cheaper.
What if you forgot multiple years?
If you missed investment income across several years, you can file a T1 Adjustment for each year going back up to 10 years. Do them in order (oldest first) since the interest compounds.
If the amounts are large or you missed foreign income or foreign assets, consider the CRA Voluntary Disclosures Program, which can reduce penalties in exchange for coming forward before CRA contacts you.
Common situations where interest income gets missed
- New HISA with a digital bank — easy to open and forget during tax season
- GIC maturing mid-year — interest is taxable in the year it is credited, not just when you redeem
- Multiple brokerage accounts — T5s arrive from each institution separately
- Foreign bank or investment account — interest is still taxable in Canada even if no Canadian slip is issued
- Held-to-maturity bonds — accrued interest may be reportable annually even before maturity
- Joint accounts — each account holder reports their proportional share
For a broader review of deductions and credits you may have missed, check the tax deductions checklist before the April 30 deadline. And if you have made other errors on your return, see I made a mistake on my tax return.