Recording of goods purchase

On the purchase value always and record a gain

Dr Purchases 1 crore

Cr. Bank 1 crore

And 

Dr. Inventory 1.5 crore

Cr. closing stock 1 crore

Cr. Gain on inventory .5 lakhs.

Maybe you can record it as a discount instead of gain because it falls within operating profits but sales is shown as net of taxes and discount. This inventory is lower of cost or nrv.so you can show discount on inventory.

I'm sort of not a complete consultant. Accounting wise it's easy. There can be company law compliances here which I am not aware of. As per AS standards you can do it like this 

Dr Purchases 1 crore

Dr. Inventory 1.5 crore

Cr. Bank 1 crore

Cr. Closing stock 1 crore

Cr. Discount .5 crore