Since the stock was gifted to you, you would have a carryover basis from the original date the person who gifted them to acquired the shares.
If you do not have
an acquisition date or basis, you can use
"0" for the basis and put "Various" for the acquisition
date. (Just make sure that you indicate that this was a long-term
capital transaction so that you get the long-term capital gains rate.)
However, you should
try to determine a basis amount because this will lower your overall gain on
the sale.
You may want to ask
the selling broker to search records for clues to help determine
basis and when acquired. If the investment was a gift, perhaps a relative got
the same gift and has records that show a purchase date.
If those options
don’t work, you may have to make an educated
guess about when the stock was purchased. You can do that by going to
the company’s website or Yahoo Finance
to find historical high and low prices for that period. (They should be
adjusted for any splits.)