delisted shares

If i hold shares and they are delisted , loss can be booked in filing incometax return

Yes, you can book loss at the time of filing the income tax return; if such shares are sold at loss.
If loss arising from such sale is Long Term Capital Loss - you can set off the same with Long Term Capital Gains.
If loss arising from such sale of Short Term Capital Loss - you can set off the same with Short Term Capital Gains as well as LTCGs.

My question is that the shares are delisted and they cannot be sold in exchange and now the value of shares has gone to zero for example Laxmi vilas bank …they are delisted and if I purchased 100 shares @ 20 then Rs 2000 can be booked as loss ? That is my question…because shares are lying in my account but value is zero.