David Note for GST

We have raised a GST Invoice to a STPI Unit in the month of Nov-2017 without charging GST as we have assumed that GST is not applicable. But now we came to know that GST is applicable for this and so we are going to raise the Debit Note for the Tax amount and declare in GSTR-3B of Feb-2018. For example Rs.1,00,00,000/- is the Taxable value @ 18%, what will be our liability. Pls clarify