STT will be same expenses as your other taxes and brokerage, Your contract note amount will be your profit and lost. You can add/deduct other expenses rent, electricity, internet etc to your contract note amount.
Yes. It is expenses and never reclaim if you are in lost in one financial year. STT was refundable 3-4 years back when you r in lost but govt change the rule.
Claim in the question i meant was showing as an expense in the calculation of income/losses from business. Yes as u say we cannot claim a refund of what STT we have paid.