Implications on pharmaceutical product Manufactured in SEZ where no excise is paid.

I am a distributor for pharmaceutical co bought goods on purchase invoice through C form paid CST and Entry tax to manufacturer. Now some goods are in mine stock and some in mine stockist stock. I had billed the goods to mine stockist @ 5% VAT and he further bill to retailer @ 5% VAT. But now since GST is to be levied @ 12% on MRP what we have to do with stock in our holding and how and whom to get credit of extra tax.