This is something you'll need to discuss with your employer or the payroll dept. 

A couple different reasons you did not have enough tax withheld: 

• you completed a TD-1 Form and stated that you had personal amounts such as Tuition, Disability Tax Credit, or a Spouse with no income, so little tax was withheld from your pay.
• Your income for each pay period was quite low, therefore little or no tax was withheld.

If you made more the year before, it makes sense that you had much more tax withheld.