T1 adjustment request: filling in and mailing Form T1-ADJ

What is a T1 adjustment request for?

A T1 adjustment request asks the CRA to change specific line amounts on a return it has already assessed. It is not a new return. The form itself says to use it when your change falls into one of the exceptions to the two online services, Change my return in My Account and ReFILE in certified software.

Those exceptions are narrow but real. Paper is the right choice when the return is for 2015 or earlier, a bankruptcy year or a year before it, a deceased person's optional return, a return filed with the wrong province or territory of residence, a return that needed Form T2203 for multiple jurisdictions, or certain international and non-resident returns. You also need paper if you cannot or do not want to use a CRA account.

How to fill out the T1 adjustment form, area by area

The current T1-ADJ has four areas labelled A to D. Wait until you have the notice of assessment for the year, then work from that notice rather than from your own copy of the return.

1. Area A, Identification. Enter your 9-digit social insurance number, the single tax year you want changed, your full name with surname first, and your address. Tick the box if it is the same as on the return.
2. Area B, Authorization. Fill this in only if a representative is making the request. They give their RepID or EFILE number, and a Form AUT-01 with access Option 2 must be on file or attached.
3. Area C, Adjustment details. For each change, give the line number, the line name, the previous amount, a plus or minus sign, the amount of change and the revised amount. Use the amount on your notice of assessment as the previous amount if the CRA already changed it. Do not recalculate your tax.
4. Area D, Certification. You or your representative sign and date the form.

Worked example: missed medical expenses

Suppose your 2025 net income was $40,000 and you forgot $2,000 of prescription and dental receipts. In Area C you would write line 33099, Medical expenses, previous amount 0, plus, amount of change 2,000, revised amount 2,000. The CRA works out the credit: for 2025 you claim the part above the lesser of 3% of net income ($1,200) or $2,834, so $800 qualifies, worth $116 federally at the 14.5% credit rate.

Supporting documents to attach

The form asks for documents that support the entire revised amount, not just the increase. If you claimed $500 of union dues without receipts and now add $20 from a late T4, you send proof for all $520. Missing paperwork is the main reason a paper request stalls.

• The new or corrected slip, for example a T4, T5 or T4A that arrived after you filed.
• Official receipts for claims such as medical expenses, donations or RRSP contributions.
• Any schedule or form the change relies on, such as Schedule 11 for tuition or Form T2203 for multiple jurisdictions.
• A short explanation in the Other details space, or on an extra sheet, if the reason for the change is not obvious from the slips.

Send photocopies and keep the originals. The CRA says to keep supporting records for at least six years in case it reviews the claim later.

T1 adjustment mailing address: which tax centre

There is no single T1-ADJ address. The back of the form (edition 23) routes you by the tax services office that serves your area. Check the chart on the copy you download, since the CRA can change routing between editions.

Non-residents, deemed residents and new or returning residents are routed by country: the form sends residents of Denmark, France, the Netherlands, the United Kingdom and the USA to Winnipeg, and everyone else abroad to Sudbury.

Is there a T1 adjustment form online?

The CRA's T1-ADJ page offers a web version of the form alongside fillable, standard and large-print PDFs, updated 9 September 2026. The form's instructions still say to send the completed form to your tax centre. If you want a truly online submission, use Change my return or ReFILE instead.

T1 adjustment processing time and next steps

The CRA publishes different figures on different pages. Its change-your-return page, updated September 29, 2026, gives 19 weeks for a mailed request and up to 35 weeks for certain requests; its May 2026 tax tip said mailed requests were being handled within the 8-week service standard; and in October 2026 its processing-times page said complex adjustment requests take up to 35 weeks and that T1 adjustment requests are delayed by higher than normal intake.

While a request is open, do not send a second T1-ADJ for the same year: the CRA asks you to wait for its response before requesting more changes. The Progress tracker in My Account shows the expected completion date for a request it has logged, which is quicker than calling.

When the CRA finishes, you get a notice of reassessment showing the changes, a reassessment with partial changes and a letter, or a letter refusing the request. If the CRA writes to ask for more documents first, see our CRA review letter guide. The after you file guide shows where a reassessment fits in the wider timeline.