Why do I owe federal income tax when my employer withheld CPP and EI?

CPP and EI deductions are fixed-rate payroll credits — they are not income tax. Your employer may have withheld far too little income tax for several reasons: (1) Multiple employers: if you worked at two jobs simultaneously in 2024, each employer applied the full basic personal amount exemption ($15,705 in 2024) independently. But you only get one basic personal amount — so you were under-withheld by thousands of dollars. (2) New job mid-year: if you started a job partway through the year, the employer annualized your salary as if you had that income all year, but also applied the full annual exemption — which may have been partially used at your previous employer. (3) No TD1 filed: your employer may have used default basic-only withholding even though you had other income sources. Owing taxes does not mean you did anything wrong — it usually means your withholding was set up for a simpler income situation.

I only had one T4 job. Why do I still owe money?

With a single T4 job and no other income, you should not typically owe taxes. But these situations can produce a balance owing: (1) Investment income: interest, dividends, capital gains, and rental income are not subject to payroll withholding. If you earned significant investment income in 2024 (outside a registered account) and no tax was withheld on it, that income is still fully taxable. (2) RRSP withdrawal: RRSP withdrawals have flat 10–30% withholding, which may not cover your marginal tax rate. (3) COVID benefits (prior years): T4A benefits (CERB, CRB) had limited or no withholding and are fully taxable. (4) Selling a property: capital gains from selling real estate, stocks, crypto, or rental property are not withheld. (5) Side gig / gig economy: Uber, DoorDash, freelancing, Etsy — no employer withholding on these amounts. (6) EI clawback: if your net income exceeds ~$79,000 in 2024, you must repay 30% of EI received up to the amount of EI received.

I have two jobs — why does this cause a tax bill?

This is the most common reason Canadians are surprised by a tax bill. Here is the exact mechanism: Federal basic personal amount 2024: $15,705. Employer A: pays you $40,000 annually, withholds tax as if you earned $40,000 total and get the full $15,705 exemption. Employer B: pays you $40,000 annually, also withholds tax as if you earned $40,000 total and get the full $15,705 exemption. Combined: you earned $80,000, but only the first ~$54,000 was taxed correctly after a single $15,705 exemption. The second employer applied a $15,705 reduction that you were not entitled to. The result: approximately $15,705 × 20–26% (combined federal/provincial rate) = $3,100–$4,000 roughly under-withheld. Solution going forward: fill in Section D of your federal TD1 form at one employer indicating you have income from another source, asking them to withhold more.

Why would investment income cause a tax bill?

Investment income earned outside a RRSP, TFSA, or other registered account is fully taxable but no tax is withheld at source: Interest income (savings account, GIC, bond) — 100% taxable, added to income from dollar one. Capital gains from selling stocks, ETFs, mutual funds, real estate, crypto — 50% of the gain is taxable (capital gains inclusion rate). Canadian dividends — grossed up by 38% (eligible dividends) for federal purposes before applying the dividend tax credit. Rental income — 100% of net rental profit is taxable income. Foreign income — foreign dividends, foreign rental income, and gains taxed at full marginal rate (no dividend tax credit for foreign dividends). If your investment accounts generated $10,000 in income and your marginal rate is 33%, you owe ~$3,300 with nothing withheld. If this is recurring, you should make quarterly instalment payments to CRA.

What are quarterly instalment payments and do I need to make them?

CRA requires quarterly instalment payments if you owed more than $3,000 ($1,800 in Quebec) in taxes in either of the two prior years AND the current year. Instalment payment due dates: March 15, June 15, September 15, December 15. If you miss instalments, CRA charges instalment interest (currently the prescribed rate + 4%) and may charge instalment penalties. How to calculate: CRA mails an instalment reminder each February and August with suggested amounts. The safest method is to pay what CRA suggests — this avoids penalties even if you turn out to owe more. If you are newly self-employed or have new investment income, you may not have received instalments yet but should start paying them to avoid owing a large amount at tax time.

I contributed to an RRSP last year. Why do I still owe taxes?

RRSP contributions reduce taxable income, which reduces your tax owing — but they cannot eliminate tax that is caused by under-withholding during the year. If you did not increase your RRSP contributions enough to offset all the extra income, you will still owe. Also: RRSP contributions only reduce taxes if you actually deduct them on your return. If you contributed to an RRSP but chose to carry forward the deduction to a higher-income year (a common strategy), you do not get the reduction this year. You can check Line 12900 (RRSP deduction) on your return to confirm whether the deduction was claimed. Finally: the deadline for RRSP contributions to count for a tax year is March 1 of the following year. Missing that deadline means your contribution counts in the next tax year only.

What happens if I cannot pay the full amount I owe by April 30?

Pay as much as possible by April 30 regardless. CRA charges compound daily interest at the prescribed rate (currently 9–10%) on unpaid balances starting May 1. Late-filing penalties are separate: if you do not file by April 30 and you owe money, the penalty is 5% of the balance owing + 1%/month for up to 12 months. The penalty is on your total balance, not just what you did not pay. Options if you cannot pay the full amount: (1) Call CRA at 1-888-863-8657 to arrange a payment plan — CRA accepts monthly instalment arrangements, especially for first-time issues. (2) Apply online through CRA My Account. (3) Interest relief: if you applied for CRA COVID-related relief historically, that is not available for current tax years. Interest charges apply regardless of plan. Filing on time, even if you cannot pay, avoids the late-filing penalty entirely.

Why Do I Owe Taxes This Year? 10 Most Common Reasons Canadians Get a Tax Bill

Owing money to CRA does not mean you did anything wrong — in most cases it simply means your employer(s) were not set up to withhold enough tax for your actual income situation.

The 10 most common causes of a tax bill

#	Cause	Why it happens	Approximate impact
1	Two or more T4 jobs	Each employer applies full personal amount exemption	$3,000–$5,000+
2	Investment income (outside RRSP/TFSA)	No withholding on interest, dividends, capital gains	Varies with income/rate
3	Self-employment / gig income	No payroll withholding on T4A Box 048 or cash	Full marginal rate
4	RRSP withdrawal	10–30% withheld; may not cover marginal rate	Difference vs. marginal rate
5	EI clawback	Net income >~$79K → repay 30% of EI received	Up to amount of EI received
6	OAS clawback	Net income >~$90,997 → 15¢ OAS back per dollar	Up to full OAS amount
7	Rental income (net positive)	100% taxable; no automatic withholding	Full marginal rate on net
8	Capital gains (selling property/stocks)	50% of gain added to income; nothing withheld	Marginal rate × 50% × gain
9	New job mid-year / career change	Overlapping personal amount credits	$1,000–$3,000+
10	Missing RRSP deduction	RRSP contributed but not deducted (or carryforward chosen)	Refund lost, not owing

Why employer withholding often falls short

Your employer calculates payroll tax based on:

Your annual salary as if you worked the full year there
Your TD1 claim amounts (personal exemptions you declared)

What your employer does not know:

That you had a second job this year
That you earned investment income
That you rented out a property
That you sold crypto, stocks, or real estate

Any income source your employer doesn’t know about goes untaxed until filing day.

How to prevent owing next year

Action	How to do it	Timing
Request extra withholding from employer	TD1 — check box “Additional tax to be deducted”	Any time before year-end
Start quarterly instalments	Pay by March 15, June 15, Sept 15, Dec 15	If you owed >$3,000 last year
Increase RRSP contributions	Contribute up to your available room by March 1	December–February
Track investment income year-to-date	Estimate gains and set aside at your marginal rate	Ongoing
Sell losing positions before Dec 31	Capital losses offset gains (tax-loss harvesting)	Before December 31

The difference between owing taxes and underpaying taxes

Owing taxes means you had taxable income that wasn’t covered by withholding — this is just a timing/collection issue.

A higher tax rate means your marginal rate increased, often because total income was higher — this is permanent.

Many Canadians confuse the two. If you owe $3,000 but your income was $5,000 higher than last year (at 33% marginal rate), you owe about $1,650 extra tax due to higher income — but you may have also had the $3,350 in your hands all year interest-free.