How is credit card interest calculated in Canada?

• Grace period: Canadian law requires at least 21 days interest-free on new purchases when the previous balance was paid in full.
• Lose the grace period: carry any balance and interest applies to new purchases from the transaction date.
• Cash advances: interest starts immediately, usually at a higher rate, plus a fee.

At 20.99%, a $5,000 balance costs about $87 a month in interest alone.