If you are a firm/sole properietor providing such services to registered person then tax has to be paid under RCM by reciever post 1.1.2019
However, in case the services are provided during Dec ’18 and the invoice in this respect has been issued during Jan ’19 in terms of section 31 of the Act (assuming no advance received); the time of supply would be Jan ’19 and the said services would be liable under RCM
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