export invoice

1. Since you intended to export the goods, you should not have paid GST @ 18% BUT should have paid @ .1% and later claimed refund of the same without mentioning anything about this tax in the export invoice.

2. Having paid GST @ 18% on the goods to be exported, you should take credit of the same. Pl mention on the invoice that the export goods are being taxed IGST @ 18%  and claim refund of this amount of tax as from the govt. This amount of tax is not to be charged from the customer based abroad.

3. Having paid the GST, you need not take the credit and claim refund of the tax paid. The goods may be exported on the strength of LUT AND input tax may be claimed as REFUND. The export invoice need not mention anything about this tax paid by you.

                    Therefore, you have both the options. if you want to pay the GST (IGST) on export of goods, then mention the rate on the export  invoice and claim refund. or else, dont mention such rate on the invoice, and claim refund of input tax. The option exercised by you will decide as to whether you want to claim refund of tax paid to the govt. or of ITC.