If you see Error Code 21 when trying to submit your tax return, don’t worry — this is one of the most common CRA rejections, and it’s easy to fix. Let’s go over what it means, why it happens, and how to resolve it in CloudTax.
What is a NETFILE Access Code (NAC)?
The NETFILE Access Code (NAC) is a unique 8-character code issued by the Canada Revenue Agency (CRA) to verify your identity when you file your tax return electronically. It acts as an additional layer of security to confirm that you are the same person who filed the previous year’s return.
You can find your NETFILE Access Code on last year’s Notice of Assessment (NOA) — it appears near the bottom of the first page, usually under the section “Access Code.”
👉 Learn more on the CRA’s official site: What is a NETFILE Access Code?
Where can I find my NETFILE Access Code?
If you can’t locate your NOA, you can:
Log in to your CRA My Account to view your code.
Refer to your paper Notice of Assessment from last year.
Contact the CRA Individual Enquiries line at 1-800-959-8281 to confirm your code.
Why Error Code 21 Appears
You’ll receive Error Code 21 if the NETFILE Access Code you entered does not match CRA’s records. This can happen due to:
Typing errors (e.g., missing or incorrect character).
Using last year’s code for a different individual (e.g., spouse’s code).
CRA updating its records and invalidating an older code.
The Purpose of the NETFILE Access Code
The NAC simply helps CRA validate your identity more securely. It is not mandatory — you can still file your return even if you don’t have it or if it doesn’t match. The CRA will still accept your return without it.
How to Fix and Submit Your Return
Call the CRA to confirm your NETFILE Access Code
Phone: 1-800-959-8281
Hours: Monday to Friday, 8:00 a.m. to 8:00 p.m. (local time)
They can verify your current code and confirm if the one you entered is valid.
Or simply remove the NETFILE Access Code
The NETFILE Access Code is optional.
In CloudTax, go to:
Menu → My Profile → Personal InformationDelete the NETFILE Access Code field and re-submit your return.
Your return should now go through successfully without Error Code 21.
In Summary
Error Code 21 = NETFILE Access Code mismatch
Fix = Either confirm your NAC with CRA or remove it from your return
Good news: The NETFILE Access Code is not mandatory, and your return will still be accepted by CRA without it.
If you continue to experience issues, our CloudTax support team can help you review your file and resubmit correctly.