My mother didn' t pay her personal taxes for a number of years. I only discovered this when I became POA and immediately set about estimating the owed amount. I  wrote a letter to CRA and enclosed the cheque. They responded with a $7000+ penalty letter to which I responded that their letter breached their own policy whereby a tax "evader" could come clean on their own and not be subject to fines.  

Suffice to say I "made" $28000/hr for the 15 minutes it took me to write and mail the letter to CRA. They never apologized for breaching their own policy.