How will the Inter-State supplies of Goods and Services be taxed under GST?

IGST shall be levied and collected by Centre on
inter-state supplies. IGST would be broadly CGST plus
SGST and shall be levied on all inter-State taxable
supplies of goods and services. The inter-State seller will
pay IGST on value addition after adjusting available
credit of IGST, CGST, and SGST on his purchases. The
Exporting State will transfer to the Centre the credit
of SGST used in payment of IGST. The Importing dealer
will claim credit of IGST while discharging his output
tax liability in his own State. The Centre will transfer to
the importing State the credit of IGST used in payment
of SGST. The relevant information is also submitted to
the Central Agency which will act as a clearing house
mechanism, verify the claims and inform the respective
governments to transfer the funds.