# Common tax-return mistakes and how to avoid them > Errors the CRA commonly corrects on personal returns, and simple habits that keep your return from being changed or delayed. - Web page: https://taxnotes.ca/guides/common-filing-mistakes/ - For: Individuals & families · Topic: Filing your return - Last reviewed: 2026-10-10 The CRA publishes tips from its review programs to cut down on the changes it has to make to returns each year. Those tips, along with the CRA's rules on late filing, point to a few problems that are easy to avoid: filing late, missing slips, claims that don't qualify and claims you can't back up. ## Filing late because you can't pay If you owe tax and file late, the late-filing penalty is 5% of the balance owing plus 1% for each full month late, up to 12 months. Interest is charged on top. If you can't pay, file on time anyway: you'll still owe interest on the unpaid amount, but you avoid the penalty. See [missed the filing deadline?](https://taxnotes.ca/guides/missed-the-deadline/) ## Waiting for a missing slip Don't hold back your return because a slip or receipt hasn't arrived. Ask the issuer for a copy, or look for it in your CRA account once the issuer has sent it to the CRA. If you still can't get it by the deadline, estimate the income and any related deductions and credits from your pay stubs or statements. Include a note with the issuer's name and address, the type of income and what you're doing to get the slip. See [slips to gather before you file](https://taxnotes.ca/guides/slips-to-gather/). ## Claiming things that aren't deductible "Other deductions" on the return is only for allowable amounts that don't have their own line. The CRA denies items that are claimed there in error, such as funeral expenses, wedding expenses, loans to family members and a loss on selling a home. ## Medical expense slip-ups - Your receipts need to be dated, marked "paid" and show what the payment was for, the patient's name and, if it applies, the medical practitioner who prescribed or provided the service. - You can't claim any part of an expense that was or will be reimbursed to you. - Over-the-counter products such as vitamins and supplements don't qualify, even if a medical practitioner prescribed them. For how to get the most from what does qualify, see [pooling donations and medical expenses](https://taxnotes.ca/guides/pooling-donations-and-medical-expenses/). ## Tuition errors - Tuition is claimed by calendar year, not school year. - Fees that were reimbursed can't be claimed, unless the reimbursement is included in income. - The receipt from the school has to clearly show the name and academic level of the course or program. - Schedule 11 goes with the student's return, not with the return of the person the student is transferring an amount to. More in [tuition credits and carry-forwards](https://taxnotes.ca/guides/tuition-credits/). ## Claiming a dependant you can't claim The amount for an eligible dependant is for people who weren't married or living common-law at any time in the year and supported a dependant living in their home. Two common mistakes: - **Claiming a child you pay support for.** If you had to make support payments for the child, you can't claim the amount for that child. - **Both parents claiming in shared custody.** When both parents qualify, they have to agree on who claims. If they can't agree, neither can claim. The CRA may ask for proof of custody, so keep it handy. ## Moving expenses that don't qualify Your new home has to be at least 40 kilometres closer to your new work or school, measured by the shortest usual public route. If you moved for work or a business, you can deduct the expenses only from employment or self-employment income earned at the new location, not from other income such as investment income or EI benefits. (Full-time students who moved for school deduct them from taxable scholarships, bursaries and research grants instead.) ## Not keeping records or not replying Keep your tax records for at least six years, even if you filed online or a form said you didn't need to attach anything. If the CRA reviews your return and you don't send the documents it asks for in time, it will review your claim with the information it has, and it may change or deny it. Its letters go to the address it has on file, so tell the CRA right away when you move. You can also authorize a representative, so the CRA can contact them if it needs more information. ## Fixing a mistake the right way If you spot an error after filing, wait for your notice of assessment. Then ask for the change: - **Online:** use "Change my return" in your CRA account, or the ReFILE option in certified tax software if you filed with software. Online requests take about two weeks. - **By mail:** send Form T1-ADJ with your supporting documents, separately from your current year's return. Mailed requests take about 19 weeks. Some changes, such as ones covering several years, can take longer. A change request can't be used to update your address, direct deposit, marital status or name; update those with the CRA directly. And no refund can be issued for a change requested more than 10 calendar years after the end of the tax year. ## Checklist - File on time, even if you can't pay. - Report every slip, or estimate a missing one. - Claim only what qualifies, and keep receipts that show it. - Keep records for six years and answer CRA letters promptly. - Fix errors with a change request once you have your notice of assessment. ## Sources 1. [Common adjustments](https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/review-your-tax-return-cra/common-adjustments.html) (canada.ca) 2. [Changing a tax return](https://www.canada.ca/en/services/taxes/income-tax/personal-income-tax/after-you-file/change-return.html) (canada.ca) 3. [Tax slips: Get a copy of your slips](https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/tax-return/completing-a-tax-return/tax-slips/a-copy-your-tax-slips.html) (canada.ca) 4. [How long should you keep your income tax records?](https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/long-should-you-keep-your-income-tax-records.html) (canada.ca) 5. [Interest and penalties on late taxes](https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/interest-penalties/late-filing-penalty.html) (canada.ca) Tax figures in this guide come from the TaxNotes.ca rates tables (https://taxnotes.ca/rates/), which cite the Canada Revenue Agency and, for Quebec, Revenu Québec. Last reviewed: October 10, 2026 How to cite: "Common tax-return mistakes and how to avoid them", TaxNotes.ca, last reviewed 2026-10-10, https://taxnotes.ca/guides/common-filing-mistakes/. For a figure or rule, also cite the official source listed above. Licence: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Free to share and adapt with attribution: https://taxnotes.ca/reproducing-our-content/