If you have a difference between your Car Stocks and Nominal Ledger then you will need to check and do the following:
Click on Reports
Click on Month End Reports
Click on Vehicles Stock Valuation Report
When you have printed the Stock Valuation Report, split it down to New , Used and Demo as it makes it a lot easier to find which one is out instead of looking at the report total for all of them.
If you are in a split period print the Stock Valuation Report to include 'Current Period' and add the future value onto YTD figure in nominal, see if you still have got difference, if not then it means something has posted into the wrong period and should be fairly easy to find.
Once you have the amount that it is out by, check the nominal transactions for this value in current and future and any transactions that would add up to this value
N: B if multi location only reconcile in single location