Cost basis is usually the amount you paid to purchase the investment.
Form 1099-B or consolidated 1099
The section total for cost basis is in the last row of the section (short-term or long-term). Look for the total under the Cost Basis (Box 1e) column. However, your consolidated 1099 might show $0 or be blank for the cost basis of employee stock.
How do I find my cost basis for employee stock?
Form 1099-DA or consolidated 1099
The section total for cost basis is in the last row of the section (short-term or long-term). Look for the total under the Cost Basis (Box 1g) column.