Correcting a Return
To change or correct a previously filed tax return, do not file another Colorado 104 return or, if you filed electronically, do not file electronically again. Use the Colorado Individual Amended Return (104X). Please be sure to check the year on the 104X form . You must use the appropriate year 104X form because the lines change on each year's form and forms for other tax years will not necessarily match the year you mean to amend.