For tax years 2009 and prior, a credit was available for the purchase of an alternative fuel vehicle, for a motor vehicle that is converted to use alternative fuel, or for the replacement of the power source with a power source that uses alternative fuel. To qualify, the vehicle must have been titled and registered in Colorado. If you were not able to fully utilize the credit in the year incurred, you were allowed to carry forward the unused portion for up to five years. This credit is no longer available to claim now, but you may claim a credit on the portion of unused carryforward from the credit you claimed during the time period in which it was allowed. See Colorado Income Tax FYI Publication Income 9 for details on this credit.