1099B cost basis

[sweetpeabg]

My 1099B shows unknow transactions for which basis is not reported to the IRS,  

The Cost or other basis is Unknown.  How do I report this as Turbotax only allows numbers in that box?

This sale also is reported under short term and long term transactions.  

[Mike9241]

this is usually from the sale of fractional shares.  unless a lot of money is involved just use $0 for the cost 

[ErnieS0]

Enter a number for your basis @sweetpeabg. Use $0 if you absolutely can't find another number, but if you do, you may pay more tax than you have to.

Check your brokerage statement or call your broker. Sometimes your statement detail or a supplement will show a cost basis even if the number is not reported to the IRS.

As super Champ @Mike9241 points out, your sales may also show an unknown cost basis because fractional shares were sold during a merger or reorganization as "cash in lieu". The cost may be $0 or it would be a fractional amount. Checking the merger announcement can offer a breakdown.

Last, if you inherited the shares or transferred them from another broker, your current broker may not know the original cost in which case you'll have to try and track down the original purchase down.

[sweetpeabg]

I did inherit this stock in 2019 after my mother's death.  Do I have to go back to her stock broker to find cost basis or do I use the price per share when I transferred it into my account?

[AmyC]

You look up the value on the date of death. See  this link. Then multiply the share price times the number of prices. Add any expenses of sale and you have your basis.