Late-filing penalty

If you owe tax for 2015 and do not file your return for 2015 on time, CRA will charge you a late-filing penalty. The penalty is 5% of your 2015 balance owing, plus 1% of your balance owing for each full month your return is late, to a maximum of 12 months.

http://www.cra-arc.gc.ca/tx/ndvdls/tpcs/ncm-tx/ntrst/menu-eng.html

Interest Rates on Balance Owing:

The interest rate charged on overdue taxes, Canada Pension Plan contributions, and employment insurance premiums will be 5%.

http://news.gc.ca/web/article-en.do?mthd=tp&crtr.page=1&nid=1041569&crtr.tp1D=1