I am unsure how to properly report the TIVO/ROVI merger from Sept 2016. Here is what my 1099-B shows:
Qty 125 shares @ 2.75/share, 1(d) proceeds $343.75
Qty 0.163 shares, 1(d) proceeds $3.50.
The TIVO stock was acquired around year 2000. Not sure original cost, my brokerage website does not show trades that old.
What is the cost basis for the above transactions and what would the cost basis be for the "new" stock if/when I sell it in the future?
For convenience I used the same 15-day average price of ROVI/TIVO as the deal used to come up with the entire "proceeds" of your sale*:
$343.75 (cash) + (125 x .3853 x $20.6344) = $1367.55. Subtracting your $2,633.13 results in a "real" loss of ($1,295.57) but because of the way the deal was structured you may not claim this loss. Accordingly in your case you'll report a "basis" of $343.75 against the cash proceeds for no gain or loss.
Since you used up $343.75 of your basis your new basis in all the new TIVO stock, including the fractional share is $2,289.38. You can use a basis of $7.72 against "cash in lieu" proceeds for a long term loss of $4.24. You basis in the remaining shares is $2,281.65.
*You could justify using a higher per share FMV based on TIVO's trading range on the day after the deal, but it doesn't change anything; you still have a loss.