contract

I have got a sub contract for maintenance from a contractor.
but he asked me to make purchases
with his gst number.
he will make me the total payment after the work.
mine it's a firm consisting of 4 partners
all the transaction will happens through bank

so can I show the purchases as loan to the contractor and pay gst for the excess amount collected from contractor as bill for services and balance treated as repayment of loan (since I could not show any purchases) ???

I have registered with gst under works contract so any issues in that??

any effect on income tax for showing as loan???