Investors & landlords
If you know your Correct Cost Basis, you can enter it in the Cost Basis entry field. Save documentation for amount entered. If you know your Cost Basis, use the regular 1099-B entry and don't indicate 'employee stock sales'.
Or, in TurboTax Online, there's a box to check for 'cost basis is incorrect', then enter the correct Cost Basis.
In TurboTax Desktop, there's a similar screen a couple screens after the original entry.
