Limit on deduction. Your allowable capital loss deduction, figured on Schedule D, is the lesser of: $3,000 ($1,500 if you are married and file a separate return), or
Your total net loss as shown on line 16 of Schedule D.
You can use your total net loss to reduce your income dollar for dollar, up to the $3,000 limit."
There is a bit more than that,but you should ask your tax preparer if only selling a portion and waiting till the following year to deduct the rest.