Gst on reimbursement of expenses incurred for client

We have got  some Client assingment for Collection of their Debtors on behalf of them. For this work we used to incur some expenses like Postage, Xerox bill, Stationery bill etc. While taking the reimbursement of this expenses from client shall we raise Invoice with GST like we raise invoice for our Service Charges of Collection of Debtors ? Pls advice.