If you have used this vehicle in the past for employment purposes, just not claimed CCA on it, you will use the Fair Market Value (FMV) of the vehicle the first year it was used for employment purposes. This number will be your UCC.
You are not required to claim CCA, and if you do not, then the value carries forward until if and when you do claim CCA. So the FMV of the vehicle, when it was first used for employment purposes, is what will have carried forward until the current tax year.
If this is your first year of using the vehicle for employment purposes, you will need to include your vehicle as an "addition" and use the FMV at this time. You will not have a UCC amount.