Sorry for the late reply as I had to pull the 2015 1099-B. It shows the sales proceeds distributed to me in 2015 (the year in which the sale occurred) but not the amounts representing the 10% holdback. Nor does the 1099-B show the gains (and whether they are ST or LT) because the cost basis and purchase dates were not provided to JPMorgan (escrow agent) by the company. I made three investments in the company: in Series A in 2008, in convertible notes in 2012 (that were later converted into Series B equity) and in Series B round that occurred in May 2015. The company was private and sold to a public company for cash in September 2015. So my take is that the last investment (May 2015 in the Series B) is the only short-term gain. The complication is that 10% of the total proceeds across all three securities were held back under the merger agreement and distributed one year later. The 10% holdback associated with the 2008 and 2012 investments is obviously LT gain. It sounds like from the initial response to this thread that the holdback associated with the 2015 investment is Short-term Gain, but perhaps is appropriate to file on the 2016 tax return since it was not reported on the 2015 1099-B?
