A measure to create a flat income tax for Kansas residents is moving ahead in the state senate.

Senate Bill 169, championed by Republican Senate President Ty Masterson, would create a 4.75 percent, flat income-tax rate.

The Kansas Reflector reports after a debate that turned bitter when a Democratic senator proposed a graduated income tax system, the Kansas Senate voted for a 4.75% flat income tax rate on a voice vote. It faces a final roll-call vote before it heads to the Kansas House of Representatives for consideration.

Senate Bill 169 would do away with the state’s current tiered income tax system in favor of one rate for all individuals earning more than $5,225 or couples earning more than $10,450. Critics claim it would cost the state $568.5 million in the first full fiscal year after it takes effect, according to the state’s estimate.

The Washington, D.C.-based Institute on Taxation and Economic Policy estimates it will cost the state $764 million.