Gst on rent

GST will be charged on 15000
reference- 15(1) of CGST Act states that the transaction value is the assesable value.

I guess it's a Commercial Property.

GST @ 18% would be applicable on Rs. 50,000/-
Refer Valuation Provision of Section 15 of the CGST Act 2017. As per the Provision of Section 15(3) clause (a) of the CGST Act 2017, Discount given by the Supplier and duely recorded in the Tax Invoice does not forms part of the TRANSACTION VALUE.

Hence GST on Rs. 50,000/- would be applicable.

Was the discount agreed upon previously?

GST WILL BE CHARGED ON 50,000 ( 1LAKH -50,000) @ 18% = 9,000/-

For the first time the land lord giving discount

whataver the case may be gst is charged on the amount of service, here amount of service is 50,000 for particular month in that case the discounted price will be eligible for calculating gst