Was the original purchase of the vehicle not entered properly as this would have looked after the HST. At this point you would have to figure which account to use to make the entry. I would use a general journal and be sure it shows on which ever report you use to report HST. This is one reason many of us do not use just the HST report as it misses any entries that were backdated. The balance sheet should show the proper dollar values for you to complete the reporting to CRA.