Gst and tds on expenses claimed

Co A sells the machines of Co B to Co C and earns commissions from both the parties. Co A is entitled to recovery of expenses incurred from Co B.

a) Does Co A need to raise the invoice and collect GST on the same and at the same time, Co B deducts TDS on the amount or 

b) Does Co A just present the details of expenses incurred and Co B discharges its liability by raising a voucher for the payment?

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