Is Input Credit available on Goods covered under Optional Scheme of Bengal regarding excise duty

We are manufacturers of Yarns and are also in Dyeing of Yarns. Our goods(Yarns) though were excisable , we were under the Optional Scheme under excise.
So when we purchased from Spinners, we received Tax Invoice and not the Excise Invoice.

What should be status of Input Credit regarding those stocks lying with us?