You, or the seller, can cancel the offer any time before you release your funds. After the funds are released, the payment is final and can't be reversed through carsales.
To cancel an offer:
Go to your offer via Account > Manage your offers
Select the offer you want to cancel
Select Manage Deal
Select Cancel
Any information on this page is provided as a guide only. It is not professional or expert advice and is not a substitute for such advice. The content may not be appropriate, correct or sufficient for your circumstances and should not be relied on as the only reason you do or don’t do anything.