I have been getting about $400 back for my tax return, but his year I have to pay back $4. Nothing has changed by year, except for salary raise. What could be the reason?

Without knowing your full tax situation, it is hard to determine why you did not receive the same refund. Perhaps you’ve missed tax credits or deductions, which is easy to do, and it can be fixed if it is necessary.

You can compare your last year's tax return to this year's tax return and you will notice if there are any differences 

If your working income was low, you may have been entitled to the Canada Workers Benefit and now that you have had a raise this may have changed. 

Differences may occur as per the Canada Revenue Agency's Indexation adjustment for personal income tax and benefit amounts

For more information please see our TurboTax article: Why is My Refund Lower Than Last Year?

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