It depends on the kind of stock.
When you enter your 1099-B information you will be asked: 'Do these sales include any employee stock? This includes ESPP, RSU, RS, NQSO, and ISO' Say yes.
Then you will be asked 'What type of investment did you sell?' Select the type.
Check the box that says 'The cost basis is incorrect or missing on my 1099-B'
Then select 'I need help figuring out my cost basis'
Depending on the type of employee stock you have ESPP, RSU, RS, NQSO, or ISO, you will be prompted for information about your basis.
If you have Employee Stock Purchase Plan stock, you will need a Form 3922, that should have been provided to you by your employer or broker.
For Incentive Stock Options, you will need Form 3921.
For Restricted Stock Units, you will need your grant information.
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