Hi,
General Rule Section 12(2) of IGST Act, 2017:- If the recipient is a registered person then the place of supply would be the location of Recipient of service. If recipient is not a registered person and address of recipient exists on record then POS would be the location of the recipient. However in case the address of recipient does not exists on record, then the place of supply of service would be the location of the supplier of service.
However as per Specific Rule 12(7), Service provided by way of Organization of a cultural, artistic, sporting, scientific, educational or entertainment event including supply of service in relation to a conference fair, exhibition, celebration or similar or events, then POS shall be If recipient is registered than location of such person, otherwise location where the event is actually held
In this case, you will charge CGST & SGST if the participant is not a GST registered person and IGST in case he is a registered person and belongs to a state other than Maharashtra.
Read more at: https://www.caclubindia.com/articles/time-of-supply-and-place-of-supply-31841.asp