If your net tax owing on your tax return is over $3000 you will be required to pay instalments the following tax year.
Tax instalments are payments you make throughout the year to cover the taxes you normally pay in one lump sum on April 30 of the following year. IF you dont pay your instalments, and you owe tax when your taxes are filed, you will be charged interest from when the instalment was due.
If you don’t pay enough instalments to cover your current taxes (and pay them by the dates required by the CRA), you will be penalized. My tip is to always over pay a little, and then there will be no penalties.
See the below CRA links for more information