It looks like TurboTax (TT) is asking for the information from Box 1 on your W-2, which is standard for calculating your taxable income.
- Box 1 on your W-2 form shows your total taxable wages, which includes your gross pay minus any pre-tax deductions like 401(k) contributions and health insurance premiums.
- Box 2a is used on forms like the 1099-R to report the taxable amount of distributions from pensions and retirement plans
For more details, you can check out the W-2 form from the IRS.