If you use TurboTax to prepare your 1040-X, TurboTax will enter the correct method.
If you are filling out Form 1004-X by hand, you have to read the instructions for Form 1040 line 16 to determine which method you should use, enter that method on the 1040-X, and use that method to calculate the tax on Form 1040-X line 6.
It is not asking what software you used. There are seven different methods that can be used to calculate the tax, depending on what types of income you have and other things in your tax return. The IRS instructions for Form 1040 line 16 explain the conditions for determining which of the 7 methods to use, starting in the right column on page 33 of the 2023 Instructions for Form 1040.
The seven methods of calculating the tax are the following.
- Tax Table
- Tax Computation Worksheet
- Form 8615
- Schedule D Tax Worksheet
- Qualified Dividends and Capital Gain Tax Worksheet
- Schedule J
- Foreign Earned Income Tax Worksheet
