How do i determine the cost basis of a gifted stock that has had reinvested dividends over the past 16 years?

[lskent]

My son received a gift of stock 20 years ago thru a grantor type trust and we opted to reinvest the dividends.  I do have the cost of the orginal stock.  We sold the stock last year - how do I determine the capital gains on the stock?  Do I take into account the cost of the stocks that were obtained from the dividend reinvestment?

[ToddL]

Since you sold all of the shares in 2017, your cost basis will be the total amount of reinvested dividends plus the cost of the original stock. 

The entire transaction can be reported as a long-term capital gain; any stock purchased less than a year before the sale would almost certainly have amounted to an immaterial part of the sale and/or resulted in an immaterial gain for a number of reasons.