Form T400A Notice of Objection: What Replaced It in Canada

If you received a notice of assessment you disagree with, you may have been told to file Form T400A. Older guides, and some letters, still use that name. The form itself has changed, so it helps to know what you are actually filling in.

This article explains what replaced T400A, the information any notice of objection needs, the deadline to check first, and the ways to file. It is general information, not advice on your own file.

This article covers Canadian federal tax law, which applies in every province.

T400A has been replaced by Form RC592

The CRA's T400A page says the form was cancelled as of 2026-10-26 and replaced with Form RC592, Notice of Objection. If you find an older copy of T400A or a guide that walks through it, treat it as out of date.

RC592 is a fillable PDF. You need to download it and open it in Acrobat Reader 10 or later, not in a web browser. Because the layout of the new form may differ from the old one, read each part of the current form itself and follow its instructions rather than relying on a description of the old sections.

What a notice of objection must contain

By law, a notice of objection must be in writing and set out the reasons for the objection and all relevant facts. The CRA's guidance lists what to include, whichever format you use:

• Your name, complete mailing address and daytime phone number.
• The notice date and the tax year being disputed.
• Your SIN, business number or other account number.
• The relevant facts and your reasons, with copies of supporting documents.
• The name and address of your representative, if you have one.
• A signature and date; for a corporation or trust, an authorized officer signs.

If you held back information during an audit or when the CRA asked for it, and only provide it with your objection, the file may be sent back for a second review. That can add time, so give the full picture as early as you can.

Check your deadline before you start

The deadline depends on who you are. An individual (other than a trust) or a graduated rate estate has until the later of one year after the filing-due date for the year and 90 days after the notice of assessment was sent. A corporation has 90 days after the notice was sent.

The 90 days run from the day the notice was sent, not the day you received it. Loss determinations and RRSP or TFSA over-contribution assessments have only a 90-day limit, even for individuals. A large corporation must also describe each issue, state the relief it seeks and give facts and reasons for each issue.

Where and how to file

The law says a notice of objection is served by addressing it to the Chief of Appeals at a CRA District Office or Taxation Centre and delivering or mailing it there. The CRA says its Appeals Intake Centre in Sudbury, Ontario receives mailed or faxed objections.

• Online: through My Account for Individuals or My Business Account, selecting "Register my formal dispute"; you receive a case number.
• Through a representative: an authorized representative, such as an accountant, can file through Represent a Client.
• On paper: send a signed letter by mail or fax to the Chief of Appeals, or deliver it in person. Form T400A was also listed as a paper option, but it has been cancelled.

The CRA says objections submitted through a secure portal are assigned to an appeals officer sooner than paper ones. Once the CRA receives your objection it gives you a case number, which should go on all later correspondence.

What to do next

• Find the notice date on your notice of assessment and work out your deadline.
• Download the current Form RC592, or choose the online option.
• Gather the notice, your return and any documents that support your position.
• Write your reasons and facts clearly, then sign and date.
• Keep proof of how and when you filed, and note your case number when you receive it.
• If the amount is large or the issue is complex, speak with a lawyer or accountant before filing.

Generally, you do not have to pay disputed income tax until the objection review is complete, though interest keeps accruing. Amounts you were required to withhold and remit must still be paid on time.

Frequently asked questions