The purpose of the Line 3 Smart Worksheet is to calculate the maximum contribution without regard to any catch-up contribution. TurboTax separately calculates the catch-up for those age 55 by the end of the tax year and on line 3 adds that to the result calculated on the Line 3 Smart Worksheet. In your case, if the birthdate that you entered for yourself into 2025 TurboTax was before January 1, 1971, the amount on line 3 of Form 8889 will be $3,975 when you indicated that you had self-only coverage for January through September..
