As per your clarification, you are holding some shares and as per AS-13, you want to revalue them as current investment and wish to know how to pass the transaction in Tally
So, same as per AS 13, revaluation of current investment should be done thgrough profit and Loss Account, So create on account Namely " Revaluation of Shares" with revenue nature and pass the entry as usual
For Upward Revaluation
Investment in SharesA/c Dr
To Revaluation of Shares A/c
Reverse for Downward Revaluation
For Tax implication on this refer IT Act
As far as my knowledge is concerned, its a capital receipt or loss and has no tax implications
Tax arises only when you transfer the shares and compute value taxable as diff between aquisition cost and Sale value
Ignore this comment if my perception of your clarification is wrong