If you cannot supply a required vehicle registration, the receptionist can collect other details first. Its next collection reply now keeps the reminder that registration is needed before the booking can be confirmed.
Keep deferred requirements clear
When required registration is unavailable, collection can move to the other details first. The next collection reply retains the reminder that registration must be supplied before confirmation.
A successful conversational reply no longer drops that reminder while asking about the next detail. The booking remains incomplete until its required information and review are satisfied.