Cost basis, how to derive

[Jonathan1]

I received 200 shares of Paramount Global on January 21, 2015.  I sold these shares on 8/29/2025. 

My 1099-B does not identify a cost basis for these non-covered securities.   As an aside, I do have cost basis information on the 1099-B for covered Paramount Global securities.  

The stock sold has had an interesting journey.  It has a genealogy of Gulf and Western, CBS and Viacom. At some point, Viacom acquired Paramount Communications.  At some point, Viacom acquired CBS.  In about 2006, Viacom and CBS split into two distinct companies.  In 2019, CBS and Viacom merged and assumed the name ViacomCBS.  In 2022, the company was renamed Paramount Global.

I am sure this has been asked before and my apologies for re-asking.  What is an IRS acceptable practice to use to identify cost basis for these shares?

[MelindaS1]

The answer to this will depend on exactly how and why you "received" rather than purchased, these shares. If you received the shares as a gift, you'll determine their basis using this guidance: TurboTax - How do I determine the cost basis of stock I received as a gift? You may also need to reference this tool. If you inherited these stocks or received them as an employee grant, entirely different basis rules may apply. See, TurboTax - Cost Basis: Tracking Your Tax Basis

Guidance on calculating the basis of stocks from the IRS:

Stocks and Bonds

The basis of stocks or bonds you buy is generally the purchase price plus any costs of purchase, such as commissions and recording or transfer fees. If you get stocks or bonds other than by purchase, your basis is usually determined by the fair market value (FMV) or the previous owner's adjusted basis of the stock.

You must adjust the basis of stocks for certain events that occur after purchase. See Stocks and Bonds in chapter 4 of Pub. 550 for more information on the basis of stock.

See IRS Pub. 551 - Basis of Assets

See also: IRS - Pub. 550, Investment income and expenses

Further guidance on noncovered securities tax reporting from Investopedia: 

Do I Have to Report Cost Basis for Noncovered Securities on My Taxes?

Yes, even though the brokerage does not report the cost basis of noncovered securities to the IRS, you are still responsible for reporting it on your tax return. You need to calculate the profit or loss from the sale of the security and report it on your tax forms, typically Schedule D of Form 1040. Failure to report the cost basis accurately could result in penalties from the IRS.

What If I Don't Know the Cost Basis for a Stock I Sold?

If you don’t know the cost basis for a stock you sold, the brokerage where you purchased the stock should have records of the transaction. Even if you didn’t keep your own records, the brokerage can provide the necessary information. You can check their website or contact the company directly to retrieve the cost basis.

[Jonathan1]

Many thanks.  I appreciate your timely and informative response.