If you have investment sale losses, after you subtract the losses from your gains you can only deduct up to 3,000 per year. You can only deduct up to 3,000 (1,500 MFS) loss per year after any gains you have. So if you have a lot of current gains you can use up the loss. The rest you will have to carryover until it is used up.
And even though you can reduce your taxable income down to zero for the regular income tax you might still owe self employment tax or the 10% early withdrawal penalty on 401k or IRA withdrawals or some other kind of tax.
