What is the T1-ADJ form?

The T1-ADJ, T1 Adjustment Request, is the CRA form used to ask for a change to a personal income tax return that has already been assessed. It is a request for reassessment, not a new return. You list the line numbers being changed, the amounts previously reported, and the revised amounts, then mail the form with supporting documents to your tax centre.

Should I file a second tax return if I made a mistake?

No. Filing a second return does not replace the first one. The CRA has already assessed the original return, so you request a change to that return instead, either online through your CRA account, through ReFILE in certified tax software, or by mailing Form T1-ADJ.

Do I have to wait for my Notice of Assessment before requesting a change?

Yes. The CRA has to finish processing the original return and issue a Notice of Assessment before there is anything to adjust. You also cannot submit a second change request while an earlier one is still being processed, so gather all of your changes and submit them together.

How far back can I request a change to a Canadian tax return?

Ten calendar years. The Minister's discretion is limited to tax years that ended within ten years before the calendar year in which the request is made, so a request submitted in a given year can reach back ten tax years and no further. Once a year falls outside that window the CRA has no authority to issue a refund for it.

When do I need to mail a paper T1-ADJ instead of changing my return online?

Mail is required when the return falls outside the range covered by the CRA's Change my return service, or when the return is a bankruptcy return or any year before the year of bankruptcy, an optional T1 return for a deceased taxpayer, a return filed with the wrong province or territory of residence, a return requiring Form T2203, or certain international and non-resident returns. ReFILE has further restrictions and cannot be used on a return that was originally filed on paper.

What can an adjustment request not change?

An adjustment request cannot be used to apply for a benefit or credit, to make or revise an election, to allocate a refund to another CRA account, or to update personal information such as your address, marital status, name, or direct deposit details. Personal information is updated separately in your CRA account. Late, amended, or revoked elections go through the taxpayer relief provisions instead.

What is the difference between a T1-ADJ and a Notice of Objection?

An adjustment request supplies the CRA with information it did not have, such as a missed slip or a forgotten deduction. A Notice of Objection formally disputes an assessment or reassessment you believe is wrong, goes to the Appeals branch, and preserves your right to appeal to the Tax Court of Canada. For individuals, the objection deadline is the later of one year after the filing due date for that return and 90 days after the date the notice was sent. Submitting an adjustment request does not pause that deadline.

Will the CRA always approve an adjustment request beyond three years?

No. Within the normal reassessment period, which is three years from the date of the original Notice of Assessment for an individual, reassessment is routine. Beyond that the CRA is exercising discretion and has published situations where it will refuse. These include increasing a permissive deduction such as capital cost allowance that was deliberately underclaimed, reopening an issue you chose not to dispute through the objection process, and changes that would increase tax on another person's return once that return is statute-barred.

03 Sep 2026 15 min read Advice

What Is the T1-ADJ and When Do You Actually Need It?

At the end of my T3 post I said "well, time to fill out a T1-ADJ" and then moved on like that meant something to everybody. But what is a T1-ADJ?

The T1-ADJ is the form you use to tell the CRA that the return you already filed is wrong and here is what it should say instead.

The single most important thing to understand up front - you do not file a second return. That is the instinct - "I got new information, let me file again properly." Do not do it. The CRA already assessed the first one. A second return does not replace it, it confuses the file, and you will spend six months untangling something that should have taken twenty minutes.

You request a change to the return that already exists. That is what the T1-ADJ is.

First Rule - Wait for Your Notice of Assessment

You cannot adjust a return that has not been assessed yet.

The CRA needs to finish processing your original return and send you a Notice of Assessment before there is anything to change. If you file on March 3rd, realize on March 5th that you forgot a slip, and immediately submit an adjustment, the system has nothing to attach it to. It gets rejected or it sits there.

Same rule if you already have a request in flight. One at a time. If you submitted an adjustment two weeks ago and then find something else, wait for the CRA to respond before submitting the second one. This is also why you should gather everything before you submit - you can bundle multiple changes into a single request, and you should.

You Probably Do Not Need the Paper Form

Here is the part that surprises people. The T1-ADJ is the fallback. There are three ways to request a change, and the paper form is the slowest of the three by a wide margin.

Method	Where	Which years	Processing time
Change my return	Your CRA account	2016 and later	About 2 weeks
ReFILE	Your certified tax software	2021 and later	About 2 weeks
Form T1-ADJ	Printed and mailed to your tax centre	Up to 10 years back	About 14 weeks

Two weeks versus fourteen weeks. That is not a small difference, and it is the entire reason I lead with this.

Change my return lives in your CRA account under Tax returns. You pick the year, pick the lines, enter the corrected amounts, and get a confirmation number. Save that confirmation number and the summary of changes. This is the default option for almost everybody.

ReFILE is built into every certified tax software product. You reopen the filed return, change the numbers, and transmit the adjustment the same way you transmitted the original. You do not have to use the same software you filed with, though it is easier if you do. ReFILE only works if the return was filed electronically in the first place - if you mailed a paper return, ReFILE is not available for that year.

The paper T1-ADJ is for everything the other two cannot handle.

So When Do You Actually Need the Paper Form?

This is the real question, and the answer is a list of specific situations.

You need to mail a T1-ADJ if the return you are changing is:

A 2015 tax year or earlier. Change my return stops at 2016. Mail is your only option, and read the section on the 10-year limit below before you bother.
A bankruptcy return, or any year before the year of bankruptcy. Talk to your trustee before you send anything.
An optional T1 return for someone who died. The final return can be adjusted online. The optional returns cannot.
Filed with the wrong province or territory of residence. You will also need to submit the forms for the province where you actually lived on December 31 of that year.
A return requiring Form T2203 - business income from a permanent establishment outside your province of residence.
Certain international and non-resident returns. Some of these you can do online now. Emigrant, immigrant, factual resident, deemed resident, deemed non-resident, and section 115 returns are generally eligible for Change my return. The rest are not.

ReFILE has extra restrictions on top of that. It cannot touch anything before the 2021 tax year, it cannot be used on a paper-filed return, and it cannot change the personal information on page one of the return. It also goes offline for a few weeks in February each year while the CRA loads the new tax year.

And there is a cap. The CRA's online system accepts a limited number of adjustments per tax year per taxpayer - the figure that circulates is nine, and it counts every adjustment to that year including ones the CRA made itself. Hit the cap and you get an automated message telling you to send the rest on paper. If you are adjusting the same year for the fourth or fifth time, you have bigger problems, but it is worth knowing the ceiling exists.

What You Can Change, and What You Cannot

You can adjust a return to:

Report income you missed - a T4, a late T3, tips, a side gig
Claim a deduction, credit, or expense you forgot - childcare, medical, moving, tuition
Add a slip that arrived after you filed - an RRSP contribution receipt is the classic one
Fix an amount you entered wrong

You cannot use an adjustment request to:

Apply for a benefit or credit (that is a separate application)
Make or revise an election
Allocate a refund to another CRA account
Update your personal information - address, marital status, direct deposit, name

That fourth one trips people up. If you moved, or got married, or changed banks, you update that in the personal information section of your CRA account. It is not an adjustment to the return.

The election restriction is the one worth pausing on. Elections are a whole separate track. Pension income splitting is an election. So is the capital gains reserve, so is a section 85 rollover, so is a bunch of stuff you might genuinely want to change your mind about. If you want to make a late election, amend one, or revoke one, that goes through the taxpayer relief provisions, not through a T1-ADJ. Different form, different process, and the CRA has discretion to say no.

How Far Back Can You Go? Ten Years, With an Asterisk

The headline number is ten calendar years. The mechanics are slightly more specific than that.

The Minister's discretion is limited to tax years that ended within ten years before the calendar year in which you make the request. So a request submitted at any point in 2026 - January or December, does not matter - can reach back to the 2016 tax year. On January 1, 2027, the 2016 year drops off permanently.

Past that, the CRA has no authority to issue a refund. Not "will not." Cannot. There is no appeal, no exception, no sympathetic agent who can override it.

But there are actually two windows here, and the difference matters enormously.

Inside the normal reassessment period - three years from the date on your original Notice of Assessment - a change request is basically routine. You submit it, they process it, you get a Notice of Reassessment. The CRA reassesses as a matter of course.

Outside that three-year window but inside the ten-year one, you are asking for ministerial discretion under subsection 152(4.2) of the Income Tax Act. The word in the statute is "may," not "shall." The CRA can decline, and there is a published list of situations where it will.

The Requests the CRA Will Refuse Beyond Three Years

This is an interesting one that doesn’t get talked about enough.

Permissive deductions. If you claimed less capital cost allowance than you were entitled to, you cannot go back after three years and claim more. Same for other permissive deductions. The CRA's position is explicit: it will not process an adjustment where the requested tax decrease comes from increasing a deduction you deliberately underclaimed. This is a real strategy killer for anybody who was managing their CCA claims year to year. Inside three years you have flexibility. Outside three years the door is shut.

Relitigating an assessment. The ten-year window is not a do-over for a dispute you chose not to have. If the CRA reassessed you after an audit and you did not file an objection, you cannot use a T1-ADJ five years later to reopen the same issue. Same if the issue already went through the objection process. The adjustment process is for new information and honest errors. It is not a second appeal.

Changes that hurt somebody else's closed year. If your adjustment would increase tax, interest, or penalties on another person's return - a spouse, a business partner - and their year is statute-barred so the CRA cannot reassess it, your request will generally be refused. Transfers of credits between spouses run into this.

EI and CPP overpayments. The ten-year relief provision does not apply to refunds of overpaid EI premiums or CPP contributions. Those have their own limits - three years and four years respectively, under their own statutes. (There is a ten-year carve-out for CPP contribution overpayments tied to retroactive CPP disability benefits.)

Somebody else's court win. If a court decides a case in a taxpayer's favour and you realize the same logic applies to your closed year, the CRA generally will not reassess you on that basis. Neither will it reassess based on another taxpayer's negotiated settlement. If you did not protect your own objection rights, watching someone else win does not help you.

Provincial time limits. Some provincial credits have their own deadlines written into provincial legislation. Federal relief does not override them.

Filling Out the Form

If you have determined that mail is your route, here is what it involves.

One form per tax year. Adjusting three years means three forms.

What it asks for - your SIN, the tax year, your name and address, authorization details if someone is filing on your behalf, the adjustment details including the revised amounts, and a daytime phone number.

For each change, you give the line number from the return, the amount previously reported, the amount of the increase or decrease, and the revised total. There is a column for explanation. Use it. "Amended T3 received April 12, slip attached" tells the assessor exactly what they need to know and gets your file through faster.

Use the amounts from your most recent notice, not your original return. If the CRA already reassessed that year and changed a figure, the number they have is the number you start from. Working from your original T1 when a reassessment has already moved a line is how you end up with a rejected request.

Attach documents for the entire amount, not just the change. This is the one people get wrong. If you claimed $2,000 in medical expenses and now want to claim $3,200, do not send just the $1,200 in new receipts. Send all of it. The CRA is reassessing the whole line, and they want documentation for the whole line - including amounts you already claimed and never had to prove the first time.

Sign it, and mail it separately from your current year return. Do not staple an adjustment request for 2023 to your 2025 return. Different processing streams, and bundling them delays both.

There is also a web version of the form on the CRA site that you fill in on screen. Handy for legibility, but confirm what it does at the end - filling a form online and submitting it online are not the same thing.

One more note on documents - if you are going the online route instead, do not send anything upfront. The CRA will contact you if they want support, and they will give you a case number. You cannot submit documents without one. Then you upload through your CRA account.

What Happens Next

Three possible outcomes:

Everything approved - You get a Notice of Reassessment showing the changes.

Some of it approved - You get a Notice of Reassessment showing what was changed, plus an explanation of what was not. If the explanation does not fit on the notice, a separate letter follows.

Nothing approved - You get a letter explaining why.

Any refund goes out as soon as the request is processed. And the timelines above are the standard cases - some requests take up to 36 weeks, including anything involving multiple returns, years beyond the three-year window, a bankruptcy return, a deceased taxpayer, a loss carryback, the pension splitting election, or any file where the CRA comes back asking you for more information.

Note what is on that list. Going beyond the normal three-year period more than doubles your wait even when everything is straightforward. Another argument for catching things early.

A Worked Example - The Late T3

Back to where this started. Say you filed your 2025 return in early March 2026, got assessed, and spent the refund.

Then in late April an amended T3 shows up for your non-registered account:

Box 26 (other income): $210
Box 21 (capital gains): $180
Box 42 (return of capital): $95

What gets added to your income is $210, plus half of $180, so $300 of additional taxable income. At a 43.41% marginal rate that is roughly $130 of extra tax.

Box 42 does not go on the return at all. It reduces your adjusted cost base. Nothing to adjust, but update your ACB spreadsheet while you are thinking about it.

Now the part that stings. Your balance was due April 30, 2026. Arrears interest runs from May 1 on that $130, compounding daily, and it does not care that the slip arrived late. Not a catastrophe on $130. But it is real, and it is avoidable by not filing in early March.

If this repeats, you might be in trouble. There is a repeated failure to report income penalty in the Income Tax Act. If you fail to report an amount of $500 or more in a year, and you also failed to report income in any of the three preceding years, you can be assessed a penalty of the lesser of 10% of the unreported amount and 50% of the understated tax net of amounts withheld. Then most provinces charge an equivalent penalty on top.

Two forgotten T3s in a four-year window is not an exotic scenario. It is the completely ordinary situation of someone who does not know T3s arrive in late March. That is the actual cost of filing early with a non-registered account, and it is why I keep hammering on this.

T1-ADJ Versus Notice of Objection

These get confused constantly and they are not interchangeable.

Adjustment request - "I have new information, or I made a mistake." You are telling the CRA something they did not know. There is no dispute. This is the T1-ADJ, Change my return, or ReFILE.

Notice of Objection - "You assessed me and I think you are wrong." This is a formal dispute. It goes to the Appeals branch, it preserves your right to go to Tax Court, and it has a hard deadline: for individuals, the later of one year after the filing due date for that return and 90 days after the date the notice was sent.

Pick wrong and you can lose real rights. Submit an adjustment request when you should have objected, watch the clock run out on your objection deadline, and you have no recourse - remember the CRA's published position that the ten-year window is not a substitute for the objection process you skipped.

If the CRA changed something and you disagree with the change, object. If you are supplying information the CRA never had, adjust.

When It Is Bigger Than a Forgotten Slip

If what you are fixing is unreported income from more than a year ago - a foreign account, rental income you never declared, a business on the side - a T1-ADJ is not automatically the right tool.

There is the Voluntary Disclosures Program, which grants relief from penalties and partial interest relief on a case-by-case basis. It is available year round, as long as what you are correcting is at least one year past the filing due date.

The critical distinction - a T1-ADJ that discloses unreported income is not a voluntary disclosure. It will not get you penalty relief, and it will not protect you from the repeated failure to report income penalty. If the amounts are meaningful or the omission was not exactly innocent, talk to a tax professional about the VDP before you submit anything. Once you have filed the adjustment, that door has closed.

The Ripple Effects

A reassessment does not just change your tax bill for one year.

Adding income changes your net income, and net income drives a long list of things - Canada Child Benefit, GST/HST credit, the Canada Workers Benefit, provincial credits, etc. Any of these can be recalculated, and if you were overpaid because your reported income was too low, you will get a bill.

It also flows to your spouse's return, if any credits transferred between you or if you split pension income.

And if the income you are adding is earned income, it generates RRSP contribution room for the following year. Small silver lining, but a real one.

Point being - check the full picture before you assume a $130 adjustment costs $130.

Short Version

The T1-ADJ requests a change to a return that has already been assessed. Never file a second return.
Wait for your Notice of Assessment first. One request at a time.
Change my return in your CRA account handles 2016 onward. ReFILE handles 2021 onward, electronically filed returns only. Both take about two weeks.
The paper T1-ADJ takes about 14 weeks and is the fallback for pre-2016 years, bankruptcy returns, optional returns for a deceased taxpayer, wrong province of residence, T2203 situations, and most non-resident returns.
Ten calendar years is the outer limit. A request made in 2026 reaches back to 2016 and no further.
Inside three years of your NOA, reassessment is routine. Beyond that it is discretionary, it takes up to 36 weeks, and the CRA will refuse permissive deduction increases, attempts to relitigate an assessment, and changes that hurt someone else's closed year.
Adjustments cannot make or change an election, apply for a benefit, or update personal information.
Attach documents for the entire line, not just the change. Use the figures from your most recent notice, not your original return.
Objection, not adjustment, if you disagree with something the CRA did. Watch the 90-day clock.
Two missed slips of $500 or more in a four-year window can trigger a repeated failure to report income penalty, federal and provincial.

Let's go back to the start. That late T3 landing in your account in April is not really a T3 problem. It is a timing problem. The reason I keep pushing "do not file before mid-April if you hold anything non-registered" is that the fix costs you fourteen weeks, a bit of interest, and - if it happens twice - an actual penalty.

The T1-ADJ exists because errors happen and the system is built to absorb them. It works. It is just slower and more expensive than not needing it.

As always - consult a professional if you are in a situation where you need to adjust your return. This post is only for information purposes and is based on publicly available information.