GST Refund

Firstly do you agree that whenever i pay output gst we pay net of ITC i.e. after adjusting ITC

TRUE...

Now, solving your example

1) If i am paying IGST on export :- Refund = Output liability - ITC available in credit ledger = 1000 - 900 = 100 ( this is the amount that you have paid to government as tax)

IN MY CASE: OUTPUT LIABILITY IS 100 DUE TO LOWER GST RATE ON EXPORT - ITC 900.... REFUND CASE NOT ARISE..

2) If i am exporting under LUT / BOND without payment of IGST : Refund = ITC in credit ledger = 900

BUT WE PAID IGST ON EXPORT AND CLAIM REFUND..

ok I will explain differently: 

GST on output: 10000 * 1% = 100

GST on Input : 9000 * 18% = 1620

we claimed refund 100 on export...how to claim Unutilized credit balance of 1520??