If I received stock as a gift many years ago (over 15), and I have recently sold a large quantity, how would I go about calculating cost basis?

[cesnell]

The one gifting the stock has passed away and I have no way of accessing their records.

[PatriciaV]

Yes, you can look up historical stock prices on either of these websites: 

• Historical Stock Quote Prices - MarketWatch
• Historical stock prices - BigCharts: Stock Charts

Use a date close to the actual date of the gift.