T3 adjustment request: send T3-ADJ or a letter, never a second T3

When does a T3 change need Form T3-ADJ instead of a new return?

Every change to the return itself goes on Form T3-ADJ. The T3 Trust Guide says that if you need to change a T3 return after you send it, don't file another return for that tax year; send Form T3-ADJ or a letter with the details instead canada.ca. The form covers both the T3RET and the T3-RCA, the Part XI.3 return for a retirement compensation arrangement canada.ca.

The rule for slips comes from the CRA's slip page: when an amended T3 slip changes the amounts on the T3RET or on Schedule 9, don't file another T3 return, send T3-ADJ or a letter giving the details canada.ca. For how each box flows to a beneficiary's T1, see T3 slip boxes, and for the allocation lines, T3 Schedule 9.

What does a T3-ADJ request need, and how do you send it?

The CRA asks for three things: the trust's account number, the tax year you want changed, and the supporting documents for the change canada.ca. A letter works as long as it carries the same details. On the form, show the line, the amount of the change and the revised amount, and have the trustee or an authorized person sign it.

You can submit it online through the Submit documents service in My Account, or as a representative through Represent a Client canada.ca. The service takes PDF, Word, Excel, JPG and TIFF files, among others, up to 500 MB in total for most programs canada.ca. To act for the trust online you need authorization first: see represent a client.

On paper, the CRA's T3 filing page sends trust returns to the Sudbury Tax Centre or the Winnipeg Tax Centre, depending on residency and the trustee's address canada.ca. Send the adjustment to the centre the trust files with. EFILE is listed for initial T3 returns only canada.ca, so a corrected T3RET doesn't go back through EFILE.

Download the fillable PDF and open it in Acrobat Reader 10 or later; the CRA warns it won't fill in from a web browser canada.ca. The form page was last updated February 27, 2026.

How long does the trust have to ask for a change?

Most trusts have three years from the date of the original notice of assessment, and a mutual fund trust has four. That is the normal reassessment period in subsection 152(3.1) laws-lois.justice.gc.ca. The guide says your request should be postmarked or electronically submitted before the period ends canada.ca.

Here's the trap. An individual can ask for a refund up to 10 calendar years back under subsection 152(4.2), but that subsection covers only an individual other than a trust, and a graduated rate estate laws-lois.justice.gc.ca. Any other trust that misses its normal period has no route to a refund through an adjustment request. The CRA reassessment period page covers the extended and unlimited cases.

Worked example: a trust with a December 31 year end filed its 2025 T3 on March 20, 2026, and the notice of assessment is dated May 20, 2026. Every clock below runs from that date, except the loss carryback, which runs from the due date of the loss year.

The 90 days count like this: 11 days left in May, 30 in June, 31 in July, and 18 in August. As of October 2026 that window has closed, but the T3-ADJ route is open until May 2029. The six and seven year carryback periods are in the guide canada.ca. The 2026 due date is on the T3 filing deadline page.

What goes out when a Schedule 9 split between two beneficiaries is wrong?

Your client's trust allocated $24,000 of 2025 income on Schedule 9: $12,000 to Anna and $12,000 to Ben. In July 2026 you find the trust actually paid Anna $16,000 and Ben $8,000 during 2025. The total allocated doesn't change, so the trust's taxable income stays the same, but two slips and Schedule 9 are wrong.

Three things go out. First, amended slips for Anna and Ben: online, change only the wrong amounts and use summary report type code A and slip report type code A; on paper, write AMENDED at the top, send two copies to each beneficiary and one to the CRA with a letter explaining the change canada.ca. Second, Form T3-ADJ for the Schedule 9 change, because the amended slips touch Schedule 9. Third, a heads up to both beneficiaries.

Anna and Ben each change their own 2025 T1. They can use Change my return in their CRA account, ReFILE through certified software, or Form T1-ADJ by mail, and each has to wait for their notice of assessment before asking canada.ca. Anna will owe tax on $4,000 more; Ben gets tax back on $4,000.

Carrying a trust loss back takes T3A and T3-ADJ together

Form T3A is the trust's request for a loss carryback canada.ca. The guide sets two conditions: make the request on or before the due date of the T3 return for the year the loss was incurred, and file T3A and T3-ADJ together, because the CRA processes them at the same time canada.ca. A T3A sent alone stalls.

The statute backs the date. Subsection 152(6) requires the prescribed form amending the earlier return to be filed on or before the day the return for the loss year is due laws-lois.justice.gc.ca. Miss March 31, 2027 for a 2026 loss and the carryback to 2025 is gone; the loss can still be carried forward.

If the trust's investment slips haven't arrived by the due date, the CRA says to estimate the income and file on time. When the actual slips differ, send them with a letter asking for an adjustment to the trust's income canada.ca.