If SEZ supplies goods to DTA unit, the DTA unit is required to file Bill of Entry and pay applicable customs duty, which also includes IGST.
The question is, whether SEZ unit will also be liable to pay GST, in addition to customs duty (which includes IGST) paid by DTA unit?
Once IGST is paid on that transaction by recipient (DTA unit), it will be inappropriate to ask supplier to pay tax on same transaction. This will be double taxation.
As per section 2(m) of SEZ Act, supplying goods to DTA is ‘export’. As per section 51 of SEZ Act overrides other laws.
Hence, it may be concluded, SEZ unit is not liable to pay any tax.