T4 Filing Deadline in Ontario: What Employers Must Prepare (Simple Checklist)

If you run payroll, T4 season isn't optional. The easiest way to create CRA problems is scrambling at the last minute—missing employee info, mismatched payroll totals, or deductions that don't tie to your books.

This guide is a practical checklist for the T4 filing deadline in Ontario—what employers should prepare ahead of time so filing is clean, accurate, and stress-free.

Quick Answer

Before the T4 filing deadline, employers should confirm employee details, reconcile payroll totals to bookkeeping, verify deductions/remittances, and prepare T4 slips + the T4 Summary.

What “T4 filing deadline” means (practically)

For most small businesses, the “deadline” isn't just a date—it's the point where you must have:

• clean payroll records,
• correct employee information,
• totals that reconcile,
• and a clear audit trail (in case CRA asks later).

If your payroll reports don't match your bank payments and bookkeeping, you'll feel it here.

Simple T4 preparation checklist (Ontario employers)

1) Confirm employee master data (do this first)

For each employee, confirm:

• Legal name (spelling matters)
• Current address
• SIN on file (as required for payroll administration)
• Employment dates (start/end if applicable)

Why this matters: incorrect employee info is one of the most common “avoidable” errors.

2) Reconcile payroll totals to your bookkeeping

Before you generate slips, make sure your year-to-date totals align across:

• payroll reports (gross pay, deductions, net pay)
• bank payments (net pay + remittances)
• bookkeeping entries (wages expense, payroll liabilities)

If these don't match, fix it now—don't “file and hope.”

3) Verify deductions and remittances (source deductions)

Review:

• income tax withheld
• CPP contributions
• EI premiums
• remittances paid vs amounts owing

Quick check: if you see payroll liabilities sitting on the balance sheet that never clear, that's a red flag to investigate.

4) Review taxable benefits (if any)

If you provide benefits or perks, confirm whether any are taxable and how they were tracked through the year.

If you didn't track them properly during the year, don't ignore them at T4 time—this is where it catches up.

5) Identify employees who left (ROE + final pay consistency)

If employees left during the year:

• confirm termination dates
• confirm final pay calculations
• ensure your records are consistent (especially if there were vacation payouts)

6) Generate T4 slips + the T4 Summary

Once your data is clean:

• generate T4 slips
• prepare the T4 Summary
• keep copies of the final slips and reports in your payroll folder

7) Save your “CRA-ready” support file (audit-proofing)

Create one folder for the year that includes:

• payroll register reports (YTD)
• remittance confirmations
• employee TD1 forms (where applicable)
• any benefit calculations
• bookkeeping reconciliation notes

This makes CRA questions easy to answer later.

Common mistakes that create CRA headaches

• Filing T4s without reconciling to bookkeeping
• Employee names/addresses incorrect
• Remittances don't match payroll reports
• “Fixing” numbers manually without documentation
• Not keeping a clean year-end payroll support folder

FAQ