Payroll and Source Deductions Audits: What Ontario Employers Need to Know

Every Ontario employer has the same three obligations for each employee's pay: withhold income tax, withhold Canada Pension Plan contributions, and withhold Employment Insurance premiums, then remit all three to the CRA on schedule. A CRA payroll source deductions audit checks whether you actually did that — correctly, on time, and for everyone who should have been on payroll in the first place.

These audits are common, often routine-feeling at first, and can become expensive fast if the CRA decides you under-withheld or misclassified workers. Understanding what the CRA is looking for — and where personal liability can attach to you as a director — helps you respond instead of react.

What a Source Deductions Audit Actually Reviews

A CRA source deductions audit typically examines:

• Payroll registers and pay stubs — confirming what was withheld against what was actually remitted
• Remittance history — whether amounts were sent on time and in full
• T4 and T4A slips — matching reported income to payroll records
• Worker classification — whether anyone treated as a contractor should have been an employee
• Taxable benefits — allowances, car benefits, gifts, or other compensation that should have been included in withholding calculations but wasn't

The audit can be triggered by a T4 filing discrepancy, a pattern of late or partial remittances, an employee complaint, or as part of a broader compliance review of your industry. Being selected does not mean the CRA has already concluded you did something wrong.

The Employee-vs-Contractor Problem

The single most expensive finding in a payroll audit is usually worker misclassification. If you paid someone as an independent contractor — no source deductions withheld, T4A instead of T4 — but the CRA decides the relationship was actually employment, you can be reassessed for the income tax, CPP, and EI you should have withheld and remitted, plus penalties and interest, going back through the years under audit.

CRA and the courts look at the substance of the relationship, not the label in your contract. The relevant factors include:

1. Control — who directs how, when, and where the work is done
2. Ownership of tools and equipment — who supplies what's needed to do the job
3. Chance of profit and risk of loss — whether the worker can profit from efficiency or lose money on the arrangement, like a true business would
4. Integration — how closely the worker's activities are woven into your ongoing operations

No single factor is decisive. A written independent-contractor agreement helps document intent, but it will not save a misclassification if the day-to-day relationship looks like employment.

Director's Liability: Why This Isn't Just the Company's Problem

If your corporation fails to remit source deductions it withheld — or should have withheld — you as a director can become personally liable for the shortfall. This is one of the more serious exposures in Ontario tax law because it reaches past the corporate shield that normally protects directors from business debts.

Director's liability for unremitted source deductions (and, separately, for unremitted GST/HST) exists specifically because these are trust funds: money withheld from an employee's pay that legally belongs to the government from the moment it's withheld, not the company's own cash. A struggling business that "borrows" from its remittance account to cover payroll or rent is creating exactly the exposure this rule targets.

If your corporation is behind on remittances, get advice quickly — the sooner the shortfall is addressed, the more options you have.

What Happens if the Audit Finds a Shortfall

Figures for interest rates and penalty percentages change and are set out in CRA's current published tables — verify the current numbers before relying on any specific figure for your situation.

Responding to a Source Deductions Audit

• Don't ignore the initial letter. Audits that go unanswered tend to escalate and narrow your options.
• Gather your payroll records early — registers, remittance confirmations, contractor agreements, and any documentation supporting how workers were classified.
• Review your contractor relationships honestly before the CRA does. If a "contractor" looks like an employee on paper and in practice, it's better to know that going in.
• Keep communications organized. Everything you send the CRA can matter later if the audit becomes a dispute.
• Get legal advice if the numbers are material or if the auditor raises misclassification, since a reassessment here can carry both corporate and personal exposure.

Frequently asked questions