Hi Uma,
If you pay the employee thru a WT and maintain his IT 0583 with Con Type 7,you should tick calc perk also and then run payroll & check, the annual car perk will be 1800/- multiply by months and driver amount based on maintained no of drivers in IT 0583 OR any other exemption amount will be seen in payslip based on your Car CC Config and Payslip config.
Try this in SAND BOX or DEV I am sure your query will be resolved.
Regards,
Venkat Polisetty.