December 15th is the day that the final personal income tax instalment for 2017 is due to be paid to Canada Revenue Agency (CRA).
If you are required to make personal income tax instalments, then you should do so. CRA’s interest is compounded daily and is not deductible. The only way that you can avoid paying interest and penalties, if you fail to pay your instalments, will be if you do not actually owe the taxes.
Most of 2017 is over. You should be able to do a pretty good estimate of how much money you have made this year and how much tax you have paid. This will help you decide if you are going to need to make any more instalments for 2017.
You only have to pay the amount of instalments that CRA asked you to pay. If you are making more money than last year, you are going to pay more tax — but you are not going to pay more instalments. The instalments are based on last year.