If you sold before the Warner shares appeared in your account, then you are right. Your basis had not been adjusted yet.
reinvested dividends add to your basis.
add all the reinvested amounts together to get the basis of reinvested dividends.
add the cost of the initial shares and any other shares you bought subsequently.
enter "Various" for date acquired and the total cost of the shares you sold, enter the proceeds.
all the long term gain or (loss) can be put on one line of Form 8949 Page 2.
dividends received within one year before you sold must be treated separately as Short Term shares.
see instructions for Form 8949 for how to use adjustment code "B" and whether you need an amount in column (g).
@gkrall
