Form ON428 Ontario Tax: Brackets, Credits, and Surtax

Form ON428 is the worksheet you use to calculate your Ontario provincial income tax, and it’s filed as part of your federal T1 General return. You work through it in stages: run your taxable income through Ontario’s five tax brackets, subtract your non-refundable credits and the Ontario Tax Reduction, then add the Ontario surtax and the Ontario Health Premium. The Canada Revenue Agency processes both federal and Ontario tax through the single T1 filing under a tax collection agreement with the province.1Justice Laws Website. Federal-Provincial Fiscal Arrangements Act

Who Files Form ON428

You file ON428 if you were a resident of Ontario on December 31 of the tax year, regardless of where the income was earned.2Canada Revenue Agency. Ontario Tax Information for 2025 Worked a contract in Alberta but kept your home in Ontario? You still file ON428 on your full income. Moved to Ontario mid-year and were living there on December 31? Same answer.

When your residential ties are split between provinces, the CRA weighs the whole picture, but the province where you kept your home and family usually wins.3Canada Revenue Agency. Determining Your Residency Status

What You Need Before Starting

You can’t fill in ON428 until your federal T1 is substantially complete. The number that drives everything is your taxable income from line 26000.4Canada Revenue Agency. Line 26000 – Taxable Income You’ll also pull your net income from line 23600, which is what the form uses to test eligibility for income-tested credits like the age amount and the spousal amount.2Canada Revenue Agency. Ontario Tax Information for 2025

Have your supporting documents ready: tuition transfer forms for Schedule ON(S11), your approved Form T2201 if you’re claiming the disability amount, medical receipts, and your most recent Notice of Assessment if you have carryforward balances. The form itself is included in the Ontario tax package on the CRA website and inside every certified tax program.5Canada Revenue Agency. Ontario – 2025 Income Tax Package

Ontario Tax Brackets

Part A of ON428 runs your taxable income through Ontario’s five progressive brackets. For the 2026 tax year, the rates are:

  • 5.05% on the first $53,891 of taxable income
  • 9.15% on income from $53,892 to $107,785
  • 11.16% on income from $107,786 to $150,000
  • 12.16% on income from $150,001 to $220,000
  • 13.16% on income over $220,000

The bracket thresholds are indexed to inflation and shift slightly upward each year.6Canada Revenue Agency. Tax Rates and Income Brackets for Individuals The result of this calculation is your basic Ontario tax before credits, surtax, and the health premium enter the picture.

Ontario Non-Refundable Tax Credits

Non-refundable credits reduce your Ontario tax but can’t produce a refund on their own. If your credits exceed your tax, the tax just drops to zero. Each credit amount is multiplied by 5.05%, the lowest provincial rate, to work out the actual dollar reduction.2Canada Revenue Agency. Ontario Tax Information for 2025

Every Ontario resident claims the basic personal amount. The other credits filers commonly claim on ON428 include:

  • Age amount, if you were 65 or older on December 31. The full Ontario age amount for 2025 is $6,223 when net income is $46,330 or less; it phases out and disappears once net income reaches $87,817.7Canada Revenue Agency. Age Amount – Personal Income Tax
  • Pension income amount, up to $1,762 for the 2025 tax year, if you received eligible pension income.8Canada Revenue Agency. Line 31400 – Pension Income Amount
  • Disability amount, if you have an approved Form T2201 on file.
  • Spousal or common-law partner transfer, where unused credits move from your spouse to you.
  • Medical expenses above the income-based threshold, mirroring the federal claim.

Tuition Carryforward on Schedule ON(S11)

Ontario tuition amounts are tracked separately from the federal amounts on Schedule ON(S11). You have to claim current-year tuition and any prior-year carryforward before transferring or carrying anything new. File a return for every year between when the tuition was paid and the year you use it; skipping years can cost you the balance.9Canada Revenue Agency. Transfer or Carry Forward Amount Once an amount is carried forward, it can’t be transferred to a spouse, parent, or grandparent in a later year.

Ontario Tax Reduction

The Ontario Tax Reduction is a separate step on ON428, and it’s the one people most often miss. It provides a $300 reduction that can zero out provincial tax for low-income filers. Taxable income up to roughly $18,930 produces no Ontario tax because of it. Above that, the reduction claws back at 5.05% of income over $18,930 and disappears at around $24,870.10Government of Ontario. Ontario Tax Reduction You claim it directly on the form; there’s no separate application.

Ontario Surtax

After credits and the tax reduction, the number left is your basic Ontario tax. If it’s high enough, the Ontario surtax kicks in. This is a tax on your tax, and it has two tiers that stack:

  • 20% of basic Ontario tax over $5,818
  • An additional 36% of basic Ontario tax over a higher, indexed threshold

When your basic tax crosses both thresholds, the top slice attracts a combined 56% surtax. That’s where Ontario’s top effective marginal rate comes from: the surtax lifts the combined rate on high earners well above the headline 13.16% bracket.

Ontario Health Premium

The last step in ON428 is the Ontario Health Premium. It’s based directly on your taxable income, not on your calculated tax, so credits can’t reduce it. It starts once taxable income passes $20,000 and scales through several bands:11Government of Ontario. Health Premium

  • $20,000 or less: $0
  • $20,001 to $36,000: 6% of income over $20,000, up to $300
  • $36,001 to $48,000: $300 plus 6% of income over $36,000, up to $450
  • $48,001 to $72,000: $450 plus 25% of income over $48,000, up to $600
  • $72,001 to $200,000: $600 plus 25% of income over $72,000, up to $750
  • Over $200,000: $750 plus 25% of income over $200,000, up to $900

The premium tops out at $900 once taxable income clears $200,600.12Canada Revenue Agency. Payroll Deductions Tables – CPP, EI, and Income Tax Deductions – Ontario

Filing Deadlines and Late Penalties

For the 2026 filing season, most individuals must file their 2025 return, including ON428, by April 30, 2026. Self-employed filers and their spouses have until June 15, 2026, to file, but any balance owing is still due April 30. Interest starts running the day after that.13Canada Revenue Agency. Due Dates and Payment Dates – Personal Income Tax

File late with a balance owing and the CRA charges 5% of the balance plus 1% for each full month you’re late, to a maximum of 12 months.14Canada Revenue Agency. Interest and Penalties on Late Taxes – Personal Income Tax A $5,000 balance filed six months late runs $550 in penalty before interest is added. If the CRA charged a late-filing penalty in any of the three prior years and issued a formal demand to file, the penalty doubles: 10% plus 2% per month, up to 20 months. Interest compounds daily on top.

How to Submit Form ON428

You don’t file ON428 on its own. It travels with the rest of your T1. Most filers submit electronically through NETFILE, or through EFILE if a preparer is filing on their behalf, which delivers faster processing and immediate confirmation of receipt.15Canada Revenue Agency. NETFILE – Tax Software for Filing Personal Taxes Certified tax software handles all the ON428 math from the information you enter.16Canada Revenue Agency. Find Certified Tax Software Paper filers mail the entire package to their designated CRA tax centre. Either way, the CRA issues a Notice of Assessment confirming both the federal and Ontario figures.

How Long to Keep Your Records

Hold onto every receipt, slip, and certificate that supports your ON428 claims for at least six years from the end of the tax year the record relates to.17Canada Revenue Agency. How Long Should You Keep Your Income Tax Records For a 2025 return filed in 2026, that means keeping records through the end of 2031. File late and the six-year clock starts on the date you actually filed. If you file a notice of objection or an appeal, keep the records until the matter is fully resolved and the further-appeal window has closed, even if that runs past six years.18Canada Revenue Agency. Where to Keep Your Records, for How Long and How to Request the Permission to Destroy Them Early The rule applies whether you filed on paper or electronically, and whether or not the CRA asked to see the documents at the time.