Sarnia Property Tax: Rates, Due Dates, and Rebates

Sarnia property tax is calculated by multiplying your property’s assessed value, set by the Municipal Property Assessment Corporation (MPAC), by a combined rate made up of a City of Sarnia levy, a County of Lambton levy, and a provincial education levy. Bills come out twice a year, with four installment due dates falling on the second-last business day of February, April, June, and August.¹ Miss one, and the penalty is 1.25 percent per month on the unpaid balance.

How Your Bill Is Calculated

MPAC assigns every Ontario property a current value assessment meant to reflect what it would sell for on the open market. You can look yours up through MPAC’s AboutMyProperty tool using the 19-digit roll number and access key printed on your Property Assessment Notice.²

That assessed value is then multiplied by three combined rates. The City of Sarnia sets the General Municipal and Transit rates through its annual budget. The County of Lambton sets the county rate, which pays for regional services. The Province of Ontario sets the education rate, which funds public schools.³ Add all three together, multiply by your assessment, and that’s your annual tax.

Because Council approves new rates every year, your bill can rise even if your assessed value doesn’t. Sarnia’s 2026 proposed budget included a 3.1 percent increase in the property tax rate over the previous year.

Due Dates and Late Penalties

Sarnia issues an interim bill early in the year based on the previous year’s assessment, and a final bill later once the current year’s budget is approved. The interim installments are due on the second-last business day of February and April; the final installments are due on the second-last business day of June and August.¹

If a payment is late, Sarnia applies a penalty of 15 percent per annum on the overdue amount, charged on the first day of default and again on the first day of each calendar month the balance remains unpaid.⁴ That’s 1.25 percent a month, the maximum Ontario’s Municipal Act permits.⁵ Penalties compound because each new charge is added to the growing balance.

Letting arrears sit is worse than a monthly fee. Once taxes remain unpaid into a second year, the municipality can register a tax arrears certificate against the property, opening a one-year redemption period. If the full balance plus penalties and costs isn’t paid by the end of that year, the property can be sold at public auction or by tender.

Ways to Pay

Sarnia accepts several payment methods:

Pre-authorized monthly plan, with a fixed amount withdrawn on the last business day of every month, spreading annual taxes over twelve payments.⁶
Pre-authorized installment plan, with each installment withdrawn on the four quarterly due dates.⁶
Online or telephone banking, by adding the City of Sarnia as a payee and using your 19-digit roll number as the account number.⁷
Cheque by mail, allowing enough time for the payment to arrive by the due date rather than just be postmarked.
A secure drop box at City Hall for after-hours payments.

Whichever route you choose, the payment must clear by the due date to avoid the monthly penalty. If your mortgage lender collects property taxes through an escrow account, confirm each year that they’ve remitted the payment on time. You remain legally responsible for the balance even if the lender was supposed to handle it.

Challenging Your Assessment

A lower assessed value cuts your tax bill every year it stays in place, so it’s worth pushing back if you think MPAC has overvalued your property. There are two stages, and the first must be completed before the second.

Request for Reconsideration

For residential properties, you start by filing a Request for Reconsideration with MPAC. There is no fee.⁸ File it online through AboutMyProperty or by mail; the deadline is printed on your Property Assessment Notice.⁹

Strong evidence includes recent sale prices for comparable homes in your neighbourhood, photos of needed repairs like foundation or roof damage, recent appraisals, and zoning information.⁹ MPAC typically responds in writing within 180 days.

Assessment Review Board Appeal

If MPAC’s decision doesn’t resolve the issue, you have 90 days from that decision to appeal to the Assessment Review Board, an independent tribunal. The residential filing fee is $132.50 per roll number.¹⁰ The Board’s decision is binding.

Rebates and Grants

Applying costs nothing and the savings can matter for anyone on a fixed income.

Sarnia Rebate for Low-Income Seniors and Persons With Disabilities

To qualify as a low-income senior, you must be at least 65 and receiving the Guaranteed Income Supplement under the federal Old Age Security Act. To qualify as a low-income person with disabilities, you must be receiving assistance under the Ontario Disability Support Program Act.¹¹ The rebate is credited to your tax account.

The deadline is the last day of February of the year following the taxation year — so for 2026 taxes, apply by the end of February 2027.¹¹ The City Treasurer’s office has the application form and documentation list.

Ontario Senior Homeowners’ Property Tax Grant

This provincial grant provides up to $500 per year to Ontario seniors with low to moderate incomes who own and live in their principal residence. You claim it through your income tax return, not through the City. The amount depends on adjusted family net income:

Single, separated, divorced, or widowed applicants get the full $500 at $35,000 or less. The grant shrinks by 3.33 percent of each dollar above that and disappears at $50,000.¹²
Married or common-law couples get the full $500 at a combined income of $45,000 or less, phasing out completely at $60,000.¹²

Charity Rebate

Ontario’s Municipal Act requires every upper-tier and single-tier municipality to rebate at least 40 percent of the property taxes payable on commercial or industrial space occupied by a registered charity, with councils free to raise the rebate up to 100 percent.⁵ Charities that lease their space can claim the rebate on the portion of taxes passed through in the lease. Registered charities in Sarnia should contact the City Treasurer to apply.

Mid-Year Changes to Your Bill

Under Ontario’s Assessment Act, MPAC can issue a supplementary assessment when a building is constructed, enlarged, or substantially improved and put into use, or when previously exempt land becomes taxable. The additional taxes are prorated for the remaining part of the year after the change.¹³

An omitted assessment covers the reverse scenario. If your property was left off the roll or under-assessed, MPAC can reach back up to two years to correct the record, and the municipality will levy the taxes that should have been charged.¹³ Renovations are the most common trigger, and the retroactive bill can be a surprise.

Buying or Selling a Property

When ownership changes hands, property taxes for the year are prorated on the statement of adjustments prepared by your real estate lawyer. If the seller already paid the full year, the buyer reimburses the seller for the remaining months; if not, the buyer receives a credit for the seller’s share.

After closing, new owners should confirm with the City Treasurer that the tax account reflects the ownership change and that any pre-authorized payment plan is updated or cancelled. The 19-digit roll number stays with the property, so the account number on the bill doesn’t change.⁷

1
City of Sarnia. Property Taxes
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Municipal Property Assessment Corporation. About My Property
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City of Sarnia. Tax Rates
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City of Sarnia. Property Taxes
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Government of Ontario. Municipal Act 2001 SO 2001 c 25
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City of Sarnia. Pre-Authorized Payment Plan Guidelines
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City of Sarnia. Questions and Answers
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Municipal Property Assessment Corporation. How to File an Appeal
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Municipal Property Assessment Corporation. How to File a Request for Reconsideration
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Tribunals Ontario. Filing an Appeal
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City of Sarnia. Rebate Programs
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Government of Ontario. Senior Homeowners Property Tax Grant
13
Government of Ontario. Assessment Act RSO 1990 c A.31