PROFESSIONAL
1777 Points
Joined September 2017
There is no difference in casual supplier or a regular supplier of goods/services except that a casual registered supplier is required to take temporary registration in the state where goods/services are to be supplied and tax is to be paid in advance in that state. Once temporary registration taken, the provisions in respect of place of supply of goods/services become applible. Pl see section 12 of IGST Act and you will get the answer.
Place of supply depends upon the location of the supplier and the location of the recipient in India. It appears from the facts given by you that the place of supply is Delhi, therefore, the IGST will be shared between Centre and Delhi. The billing address is not important.