A number of clients approached me initially because

1. A CRA letter demanded them to file and the letter stated that they might be prosecuted if they did not file by certain time frame.

2. CRA garnished their bank account because they got arbitrarily assessed by CRA with a big owing balance.

3. Bank needed to see their tax status prior to approve their mortgage (or equity loan) applications.

4. Service of Canada needed to determine whether they were capable to sponsor their beloved ones to immigrant to Canada.

Whichever reason, one in common, they did not know where to start and were scared of potential tax bill and unknown late filing penalties and interest on top of everything.
Other than the ones who received CRA letter to demand them to file, in most cases, taxpayers could take benefit of Voluntary Disclosures Program (VDP) to get everything caught up without paying late filing penalties and only pay the minimum interest if you end up having owing balance instead of refund. Check VDP out by clicking on the link below.

http://www.cra-arc.gc.ca/voluntarydisclosures/

Behind with your tax returns?