Let me share what I know about disallowable expenses, Heatheremma2003.
Once you enter expenses manually in QuickBooks Self-Employed and set them to car/vehicle expense (rather than using the mileage tracker), it will be categorised as disallowable. Only travel expenses will be allowable.
I'll add this reference to help you categorise the transactions you download from your bank or enter into QuickBooks: Categorise transactions in QuickBooks Self-Employed.
Reach out to us again if you have other banking concerns. We'll reply as soon as we can. Keep safe!