Tax arrears are property taxes that remain unpaid after their due date. Arrears accumulate when property owners cannot or do not pay taxes, with penalties and interest adding to the outstanding balance. Municipalities track arrears carefully as they represent uncollected revenue that can affect cash flow and budgets. Arrears collection involves progressively serious measures: reminder notices, penalties, interest charges, payment plans, and ultimately tax sale where properties can be sold to recover unpaid taxes. Some arrears result from financial hardship, prompting municipalities to offer payment plans or connect owners with assistance programs. Tax arrears rates (percentage of taxes uncollected) vary by municipality and economic conditions, with higher rates during economic downturns.