Cost basis is the original value of an investment, typically the price you bought it for. It’s used to calculate capital gains or losses when you sell the investment.

Cost basis can be adjusted downward by subtracting any capitalized costs directly related to the asset. Common expenses that reduce an asset's cost basis include depreciation, damage to the asset ...

Your W-2 does not list your adjusted gross income, but it contains the information you need to calculate your AGI. Box 1 lists your total income earned from your employer.