You filed your T4A slips, breathed a sigh of relief… and then noticed a mistake.
Maybe a contractor’s name is spelled wrong, a SIN is missing, or an amount is off. The natural question is:
“Can I correct a T4A slip after filing, or is it too late?”
The good news: in many cases, you *can* correct a T4A after filing. The key is to fix it properly, document what happened, and learn from it so the same issue is less likely next year.
This guide walks you through a practical, non-technical approach to handling T4A corrections.
(For exact procedures and codes, always refer to current CRA instructions or speak with your accountant.)
Step 1: identify what kind of error you’re dealing with
Not all errors are created equal. Start by classifying the problem:
• Minor clerical errors
– Small typos in names, slightly off addresses, formatting quirks.
• Data errors that affect the contractor
– Wrong amount in a box
– Missing or incorrect SIN or business number
– Slip sent to the wrong person
• Structural or filing errors
– Wrong reporting year
– Duplicate slip filed for the same contractor
– Entire groups of contractors missing
The bigger and more material the error, the more important it is to follow CRA’s official correction process carefully and keep good records.
Step 2: confirm the correct information
Before you change anything, make sure you know what the *right* information is. That usually means:
• Pulling the original invoices, payment reports, or contracts.
• Confirming totals from your accounting system.
• Verifying contact and tax details directly with the contractor if needed.
You don’t want to submit a “correction to the correction” because you rushed this step.
Step 3: talk to your accountant or check CRA guidance
Once you know what needs fixing, touch base with your professional advisor or CRA resources to confirm:
• Whether a corrected slip should be issued.
• How to mark a slip as amended in your chosen filing method.
• Whether any additional forms or explanations are needed.
For example, in many cases you’ll:
• Prepare an amended T4A slip with the corrected information.
• Mark it clearly as an amended slip (not a brand-new original).
• File it electronically or via CRA-approved methods.
Your accountant can tell you the exact codes and electronic file requirements for your situation.
Step 4: update your internal records and systems
A corrected slip should always match your internal records. After you fix the error, make sure you:
• Update contractor details in your contractor database or T4ASlip.
• Correct the underlying accounting entries if they contributed to the mistake.
• Ensure your year-end workpapers reflect the corrected amount and slip.
That way, if CRA asks questions later, everything lines up.
Step 5: inform the contractor
If the error affects the contractor (for example, wrong amounts, incorrect name, or missing SIN), let them know:
• That there was an error on their original slip.
• That you’ve filed a corrected slip with CRA.
• When they can expect to receive the updated copy.
This is especially important if they’ve already filed their own tax return—your amended slip may mean they need to adjust their filing. Your transparency helps them avoid confusion and mismatches on CRA’s side.
Common examples of T4A corrections
Example 1 – Wrong amount in box
You accidentally reported $12,000 instead of $21,000 for a contractor.
• Confirm the correct total by reviewing invoices and payment reports.
• Prepare an amended slip with the correct amount.
• File the amendment with CRA and send the updated slip to the contractor.
• Document what caused the error (for example, missing payments in the original report) and adjust your process next year.
Example 2 – Contractor name or address change
A contractor moved or changed their name after you issued the original slip.
• Verify the new legal name or mailing address.
• Follow CRA guidance on whether and how to update minor details.
• Update your systems (accounting, T4ASlip, CRM) so future slips are correct.
Example 3 – Duplicate slip
You accidentally filed two slips for the same contractor with overlapping amounts.
• Identify which slip is correct.
• Work with CRA or your accountant to void or correct the duplicate.
• Update internal records so only the correct slip remains.
Reducing the need for corrections in the future
Corrections are sometimes unavoidable—but often, they point to process gaps. You can lower the odds of repeating the same mistakes by:
• Collecting contractor information at onboarding, not at year-end.
• Using consistent reports from your accounting system instead of manual tallying.
• Implementing a review checklist before filing.
• Using a dedicated tool like T4ASlip to validate data and centralize contractor details.
Each small improvement reduces your “error surface area” and makes your T4A filings cleaner over time.
How T4ASlip helps with both prevention and correction
T4ASlip can support you in two ways:
Prevention
• Ensures contractor profiles are complete (names, addresses, IDs).
• Summarizes payments by contractor from your data.
• Flags missing or inconsistent information before slips are generated.
Correction
• Gives you a clear view of the *original* data used for T4As, making it easier to see what went wrong.
• Allows you to update contractor records so future years don’t repeat the same mistake.
While the formal correction filing still goes through CRA, T4ASlip helps you manage the information side of the fix.
Bottom line
Yes, you can usually correct a T4A after filing—but the right steps are:
1. Identify the type and size of the error.
2. Confirm the correct information.
3. Follow CRA’s official processes for amended slips.
4. Update your internal records and inform affected contractors.
5. Adjust your process so the same issue is less likely next time.
Treat each correction not just as a fix, but as a chance to strengthen your T4A workflow going forward.