Income Tax Implications in case of Meger of Subsidairy with Parent Company as per the IT Act

Our subsidairy company owns office premises, which it has rented to Parent Company. Parent Company is showing a Interest free loan in its books to the Subsidairy. The land on which office has been constructed originally belonged to MSRTC. The Subsidairy Company does not have any sale/revenue of its own. No transactions in its books. Dear Experts, kindly advise regarding the accounting entries in books of Parent Company and Subsidairy Company in case of Merger. Kindly advise with respect to percentage of stamp duty in case Subsidairy is merged with Parent Company & its calculation