Got no cost basis on 1099-B. If left blank on TT, it will list is as "info needed". Does this increase chance of audit? I couldn't get cost basis from Computershare.

Reporting a cost basis of $0 would not increase your chance of being audited. It will just increase your capital gain and cause you to pay more tax.

You can calculate the cost basis of the fractional share resulting from a merger.

For example, if you had 100 shares of ABC with a cost basis of $200. Then those 100 shares of ABC are exchanged for 5,25 shares of XYZ. So the cost basis remains the same for the 5.25 shares of XYZ at $200. Therefore, the 0.25 fractional share has a cost basis of $200/5.25 x 0.25 = $9.52.

Thanks MinhT1,

Is there a concern if Computershare didn't report a cost basis and I show one?

Paul

No, it is not uncommon that taxpayers need to make price adjustments in connection with mergers, acquisitions, reverse stock splits, etc.  Make the necessary adjustment as suggested by @MinhT1.  While the amount may have only a minor impact on your taxes, your return will be accurate as long as the adjustment is warranted.

Keep the records that you have in the event you may need to explain your justification for making the adjustment. 

@pginotti