What's the impact of incorrectly filling out the TD1 form have on my tax return?

[huy-tran]

When I landed my part-time job back in 2013 I was in college so I checked the "Total income less than total claim amount" box on my TD1 forms because I was making less than the claim amount. 

However, in 2014, I graduated and was employed full-time at another company.  I still kept the part-time job but did not update the "Total income less than total claim amount" option even though it was no longer true.  As such, taxes were not being deducted from my earnings for my part-time job.   Also, I did not check the "More than one employer or payer at the same time" option on the TD1 form for my part-time job since I already claimed the tax credit on the TD1 forms for my full-time job. 

For the entire year, I only made around $3600 at my part-time job.  How does this affect my 2014 return (ie. what will I be charged with?)?  Thanks for taking the time to answer my question.

[TonyC11 · Accepted solution]

If you are not being deducted for tax on your p/t employment, you will be liable for tax at whatever your combined federal and provincial rate is.
Let's say as a new employee in Ontario this rate would be just over 20%, you will owe about
$720 on your part-time earnings.

Some of this may be offset by any Tuition credit carryforward you had. That amount must now be used to offset 2014 taxes.

Going forward, if you continue with your p/t, you might want to resubmit a TD1 with a request to deduct 20% tax at source.