Ask for the plate after you offer a time
Customers arriving through a booking screen will often abandon when the first required field is a registration number they cannot remember while standing in a car park.
In one Permas Jaya lane, reversing the order — time slot first, plate second — recovered a visible share of unfinished requests inside the same month. The app vendor had always allowed either order; the workshop had simply copied a dealership template meant for warranty claims.
Before redesigning your entire flow, print the first three screens a customer sees. If the plate arrives before the promise of a bay, test moving it down.