If you are registered under normal scheme than you can freely sale your good/services in any state but under composition interstate sale not allowed. For purchase no need of registration.
as amit and neha says that true in case of composition registered dealer can purchase goods from.any state but from 26 july some state generate own e way bill software
in up and gujrat if Dealer purchase from outaide from state and goods value is more then 5000 then e way 1 bill also be attach for declearation of purchase from other then state
in composition scheme sec 10 will says dealer cant generate any invoice for tax collection
so Igst will not transfer in compisite scheme for Composit dealer
coz of that dealer cant sale to other then state
in purcase of otherthen state eway 1 bill is nasessery for normal and Composit dealer for more information my contact at whatapp no 9457257157