I am not GST expert, still I try to give answer to your query on the basis of basic knowledge I acquired on GST.
Though there are many grey areas in some provisions in the GST, as far as salary is concern or the cost on employment is concern, there is no impact of GST, in general.
In case of supply of free goods or services to an employee exceeding the stipulated sum or if an employee avails of company asset for personal use say a car, a house etc., it would trigger GST.
The mechanism of input credit under GST i.e. input tax credit will not be available on supply of various facilities to employees, including life and health insurance.
You need to take expert advise on formulating CTC structure if it includes certain costs of facilities / fringe benefits.
From India, Mumbai