Sir,
GST @ 5% without ITC means the service provider cannot avail ITC in respect of inputs and input services used for providing the output service (Renting of motor cab). If he pays 12% gst then he can avail ITC in respect avail ITC of inputs and input services used for providing the output service (Renting of motor cab). AT whatever rate the service provider pays gst the same can be availed by the service receiver if he uses the motor cab in the course of or furtherance of business. If the client uses the motor cab for his personal use then he is eligible to avail ITC.
As per Section 17 (5) (a) of CGST Act, 2017-
Notwithstanding anything contained in sub-section (1) of section 16 and subsection (1) of section 18, input tax credit shall not be available in respect of the following, namely:-
(a) motor vehicles and other conveyances except when they are used––
(i) for making the following taxable supplies, namely:-
(A) further supply of such vehicles or conveyances ; or
(B) transportation of passengers; or
(C) imparting training on driving, flying, navigating such vehicles or conveyances;
(ii) for transportation of goods.