Yes you can make interstate purchase from unregistered person, but need to pay IGST under RCM. By the way, unregistered person need to obtain registration to make interstate outward supplies.
chatCommentsMy supplier is based in Gujarat however we are based in Delhi.We have acquired registration but ur supplier will be applying for registration next week.But we have made few purchases from him in this week..So how should we treat this transaction i.e under rcm basis or can he issue invoice after a week once he gets his registration done? - Avi SharmaAs per rules invoice should have been issued. Since you got it from unregistered person pay tax under RCM. - Pulkit Sharma