Does Tax Software Find All Your Deductions?

How Tax Filing Software Actually Works

Tax filing software is built around a simple principle: you provide the information, and it calculates the tax correctly. It will ask you a series of questions — did you work from home? Do you have children? Did you make RRSP contributions? — and then apply the right CRA rules to whatever you answer.

This model works well if you know exactly what happened in your financial life last year and you know which questions to pay attention to. The problem is that most people do not know every deduction and credit they might qualify for. And the software cannot know what you have not told it about.

If you moved for work but did not think to mention it, TurboTax will not ask. If you paid for your child's therapy and did not realize it qualifies as a medical expense, Wealthsimple will not flag it. The software is reactive, not proactive.

The Gap Between “Filed Correctly” and “Optimized”

There is an important distinction between a return that is correct and a return that is optimized. A correct return accurately reports what you told the software. An optimized return captures everything you are actually entitled to claim.

According to H&R Block's own research, roughly half of Canadian taxpayers file returns that miss something. The average missed amount is around $2,900. These are not errors — the returns are accurate — they are simply incomplete because the filer did not know to claim certain items.

This is not a criticism of the software. It is a structural limitation of any tool that relies on the user to know what to input. The software cannot see your life — only what you choose to share.

Common Deductions Tax Software Misses

These are the credits and deductions that most commonly fall through the cracks when people file on their own — not because the software cannot handle them, but because filers forget to bring them up:

• Medical expenses for dependants — Expenses paid for parents, grandparents, or adult children with disabilities are claimable, but people often only think of their immediate household.
• Work-from-home detailed method — Most people take the flat rate ($2/day) without calculating whether the detailed method, based on actual rent and utilities, would be significantly larger.
• Moving expenses — Claimable if you moved 40+ km closer to work or school. People forget about temporary storage, hotel stays during the move, and lease cancellation fees.
• Union and professional dues — Fully deductible, but sometimes not itemized on a T4 and easy to forget.
• Canada Training Credit — A newer credit (introduced 2020) that accumulates at $250/year. Many Canadians have never heard of it.
• Interest on student loans — Only government student loans qualify, but the credit is non-refundable and can be carried forward five years. Graduates often forget to keep claiming it.
• Carrying charges and investment expenses — Management fees paid outside of registered accounts, interest on loans used to earn investment income, and certain advisory fees are deductible.

None of these require special expertise to claim. They just require knowing they exist — which is the part that tax filing software does not reliably provide.

The Smart Approach: File Yourself, Then Check

You do not need to abandon the software you already use or hire a professional for your entire return. The smarter approach is to file as you normally would — using whatever free or paid tool you prefer — and then review your completed return against the full range of deductions and credits available to you.

Filing your own taxes keeps you in control, costs little or nothing, and is entirely appropriate for the vast majority of Canadians. The missing piece is the audit step: comparing your completed return against your actual situation to see what got missed.

And if you find something? Under CRA rules, you can amend your return for the past 10 years. The missed deductions from 2022 or 2019 are still claimable today.