“Unused credit carryforward” is any credit amount that you earned in a previous year, less any credit that you applied to unpaid tax in following tax years, less any credit that has expired. For example, if you earned a Dependent Care Assistance Program Credit in 2018 the amount of $5,000, and you used $2,000 credit on your 2018 x return, you had $3,000 left to carry forward for two years. On your 2019tax return, you used $1,500. You now have $1,500 left to use on your 2020 tax return.This is your unused credit carryforward. If you are not able to use all $1,500 on the 2019 return, you will forfeit the excess credit.