@subodh66 -
you can not simply sell $30k of stocks with a cost basis of $10k and then decide not to net the gain against the loss carryfoward. That would mean you wouldn't pay any tax on the gain (because your income was a 0% capital gains rate) and still preserve all the loss carry forwards for a future year. The IRS is too smart for that. You have to consume the loss carryforward with the gain so you don't achieve that advantage for the future.
