If there is an increase or a decrease in how much you use your car in your enterprise, this will result in a change to the GST credit you are entitled to claim.
You should check the business use of your car for each period for which you prepare a BAS. If there is a change over time in the percentage you use your car for your enterprise, a GST adjustment may be required. This is not something we can currently assist you with through Airtax.