A pleasant surprise awaits Coloradans when they file their taxes this spring: a reduced tax rate of 4.5 percent (rather than the usual flat rate of 4.63 percent) will apply to income earned in 2019. This temporary income tax rate reduction, which will be enjoyed by individuals, pass-through businesses, and corporations alike, was triggered because state tax collections exceeded the Taxpayer’s Bill of Rights (TABOR) revenue limit by $428 million in fiscal year (FY) 2019.

TABOR, enshrined in the state constitution since it was approved by voters in 1992 (but amended by a an increased “Referendum C” cap in 2005), places an annual limit on state revenue growth, capping it at the prior year level after adjusting for inflation, population growth, and any voter-approved revenue changes. Any collections above that limit, by default, are returned to taxpayers unless a majority of voters authorize the state to retain the surplus.

The Colorado Constitution does not prescribe specific refund mechanisms but instead authorizes the General Assembly to make those determinations. Under current law, TABOR surpluses can be returned to taxpayers using up to three refund mechanisms: a property tax exemption reimbursement to local governments, a “sales tax refund,” and a temporary reduction in the state’s income tax rate. The income tax rate reduction is the most difficult to trigger since it requires the largest amount of revenue.