Hire purchase agreements: consideration: purchaser
If you are dealing with the purchaser, then the hire charges are not treated as part of the acquisition cost of the asset for Capital Gains Tax purposes. Where the purchaser is a trader, then these payments may be allowable deductions. BIM45350 onwards tell you about this.
Failure to complete payments
Most hire purchase agreements allow the vendor to repossess or recover the asset if the purchaser fails to pay the full amount of the hire charges. If you have a case where the asset has been repossessed and the sums received by the vendor are treated as capital then you may need to revise the Capital Gains Tax computation. You do this by only including the amount which the vendor actually received. Where appropriate, any tax should be discharged or repaid.