I'm a common shareholder in a US private company acquired in Nov 2017 by a US public company. I'm planning to wait until Jan 2018 to exchange my shares for cash+stock in the acquirer. (The M&A proceeds-- cash and stock-- are currently being held at an escrow company who's waiting for me to give them to go-ahead to do the exchange.)
If I don't do the exchange util January 2018, then are my capital gains taxable in 2017 or 2018? In other words, is the sale date considered to be the date that the M&A transaction closed, or the date that I actually exchanged my private-company shares for the M&A proceeds (cash + acquirer stock) ?
If it matters, the escrow company has told me that the Sale Date on the 1099-B they send me will be the date of the exchange (Jan 2018), not the close date of the acquisition (Nov 2017).