Colorado Sales Tax Increase on Ballot August 14, 2008 Joseph Bishop-Henchman Joseph Bishop-Henchman This November, Colorado voters will decide Amendment 51, which will raise the state sales tax from 2.9% to 3.1% over two years. The estimated $186.1 million per year raised by the tax increase would be dedicated to services for the developmentally disabled. More on Colorado here. Stay informed on the tax policies impacting you. Subscribe to get insights from our trusted experts delivered straight to your inbox. Subscribe Share Tweet Share Email Topics Colorado Sales Taxes Tags State Tax and Spending Policy