Yes, you correctly indicated 'cost basis is incorrect or missing' in TurboTax when entering your 1099-B for sale of inherited stock, since it is blank on your form. On the next screen, you can then enter the correct Cost Basis.
The Cost Basis is the value of the asset at the time of the decedent’s death, which may the Cost Basis reported on on the additional document you received, and which you could then enter in TurboTax.
You could confirm that with the Broker, or look up the value of the stock on the Date of Death online.
Here's more info on Stock Cost Basis.
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