Tax interest refers to interest charges that accumulate on unpaid property taxes, adding to the outstanding balance over time. Interest rates on tax arrears are typically set by provincial legislation or municipal bylaw, often higher than market interest rates to discourage delinquency. Interest continues accruing until taxes are paid in full. Unlike one-time penalties for late payment, interest compounds over time, making long-term arrears increasingly expensive. The interest rate and calculation method (simple or compound, monthly or annual) affect how quickly balances grow. Some municipalities distinguish between interest (ongoing accumulation) and penalties (one-time charges for late payment). Understanding tax interest helps property owners appreciate the cost of unpaid taxes and the importance of addressing arrears promptly.