Consultancy service query

Transaction value include

Value of services and any other value which is ancillary to such amount

(Example – Out of pocket expenses, Stationary and other Expenditure)

And hence, the stationary expenditure can be added in your bill and GST shall be collected on total value (i.e Value of services + Other expenditure)

Your Question

“Any expenses incurred by professional supplying services (for eg stationary expenses incurred) can such professional include such expenses in his invoice on which already gst is charged”

Answer is yes

GST Valuation Rule 

Value of Supply Rule 

you can refer both for better understanding