Yes, my issue was with Tencent. Showing the cost basis as zero basically ensures that you don't underestimate taxes due. Since the amount of my tax on this distribution was on the order of $20 it was just not worth my time and effort to pursue further. Regarding the dates, you just have to establish whether it was short term or long term gain. In my case, the brokerage notes indicated this was clearly long term so I just made up a date in this timeframe, consistent with the brokerage notes. Short term would be for assets held less than one year I believe.
