No. It is not possible. Your description is binding from the moment you have registered the car. You cannot change the description or withdraw the car while the auction is in progress. Although this may sound unforgiving, you must remember that the dealer's bids are also binding. The dealers who place a bid on your company car, are doing so on the foundation of your description (as it exists from the moment they bid). If you could later add, for example, that the car did not have air conditioning after all, this may have resulted in the dealer not placing a bid in the first place or at least provided a lower offer. In the unlikely event that your company car is not sold, you naturally have the option to change both the description and the reserve price, before placing it on auction again. It might, for example, be relevant to change the mileage figure if you have been using the car.