Has this person filed or have they not filed?
From CRA...
Interest
If you have a balance owing for 2012, we charge compound daily interest starting May 1, 2013, on any unpaid amounts owing for 2012. This includes any balance owing if we reassess your return. In addition, we will charge you interest on the penalties starting the day after your return is due. The rate of interest we charge can change every three months. See Prescribed interest rates.
If you have amounts owing from previous years, we will continue to charge compound daily interest on those amounts. Payments you make are first applied to amounts owing from previous years.
Interest on unpaid taxes may be waived or cancelled under certain circumstances. See Taxpayer relief provisions.
Late-filing penalty
If you owe tax for 2012 and do not file your return for 2012 on time, we will charge you a late-filing penalty. The penalty is 5% of your 2012 balance owing, plus1% of your balance owing for each full month that your return is late, to a maximum of 12 months.
If we charged a late-filing penalty on your return for 2009, 2010, or 2011 your late-filing penalty for 2012 may be 10% of your 2012 balance owing, plus 2% of your 2012 balance owing for each full month that your return is late, to a maximum of 20 months.
Tax Tip
Even if you cannot pay the full amount of your balance owing on or before April 30, 2013, you can avoid the late-filing penalty by filing your return on time.
These opinions are entirely my own and do not represent any other person or organization.