The rollback tax rate calculation splits the tax rate into two separate components - a maintenance and operations (M&O) rate and a debt service rate. M&O includes such things as salaries, utilities and day-to-day operations. Debt service covers the interest and principal on bonds and other debt secured by property tax revenues. 1 The rollback tax rate is the sum of M&O and debt service rates. 2 In most cases, the rollback tax rate exceeds the effective tax rate, but occasionally decreases in a taxing unit's debt service will cause the effective tax rate to be higher than the rollback tax rate.