this is a ridiculous thing that i deal with every year. Basically i make an educated guess. Brokerages do provide the cost basis, but only started keeping that info for the past ten or fifteen years. One year i went through and approximated the cost basis of all my investments and all the foreign stocks as well. Then i put a round number in the space for total and foreign investments. Then, i have to look up what i did last year. I'll use the same numbers or add a little to it, and put in for this year line 4 b (1) b and c of form 116. I can't see the significance unless it is for a macro economic issue.
