Updated October 18, 2026. Quick answer: Line 3 adds lines 1 and 2. A yes or no question then decides your path. If you took no traditional IRA distribution and made no Roth conversion, line 3 goes on line 14 and Part I ends. If you did, line 4 removes contributions made in early 2026 and line 5 is the result.
Line 3: the starting total
The form says “Add lines 1 and 2”. That combines this year’s nondeductible contributions from the line 1 page with the basis carried in on the line 2 page. The instructions have no separate paragraph headed Line 3, so the form’s own caption is the whole rule.
The question between lines 3 and 4
Between the lines the form asks “In 2025, did you take a distribution from a traditional IRA, or make a Roth IRA conversion?” The first answer is “Enter the amount from line 3 on line 14.” “Do not complete the rest of Part I.” The other answer is “Go to line 4.” Distributions are covered on the line 7 page and conversions on the line 8 page.
Line 4: contributions made in early 2026
The caption reads “Enter those contributions included on line 1 that were made from January 1, 2026, through April 15, 2026.” The instructions let you choose how to label contributions when you have both kinds: “you can choose to treat the contributions made in 2025 first as nondeductible contributions and then as deductible contributions, or vice versa.”
Their example reads: “You made contributions for 2025 of $2,000 in May 2025 and $2,000 in January 2026, of which $3,000 is deductible and $1,000 is nondeductible.” It continues: “You enter the $1,000 on line 1, but not line 4, and it becomes part of your basis for 2025.” The instructions also explain why line 4 exists: “they aren’t included in figuring the nontaxable part of any distributions you received in 2025.”
Line 5 and where it goes next
The form says “Subtract line 4 from line 3”. Line 5 then becomes the top of the fraction on line 10 and part of the distribution math described on the lines 9 to 14 page. The instructions have no separate paragraph headed Line 5. If you skip Part I’s remaining lines, line 3 goes straight to line 14.
Edition and line numbers
This page reads the 2025 Form 8606 and its 2025 instructions, the current files irs.gov served on 2026-10-18. They are the files for the tax year 2025 return, filed in 2026. The form says “Attach to 2025 Form 1040, 1040-SR, or 1040-NR.” Check the tax year printed on the form you are filling in and use the line numbers on that year’s form, because a different year’s form can number or word its lines differently.
Common mistakes
- Completing the rest of Part I when nothing was distributed or converted. The form says “Do not complete the rest of Part I.” for the no answer.
- Dropping early 2026 contributions from line 4 when they belong there. The caption says to enter “those contributions included on line 1 that were made from January 1, 2026, through April 15, 2026.”
- Counting April contributions in the 2025 distribution math. The instructions say “they aren’t included in figuring the nontaxable part of any distributions you received in 2025.”
Related: Form 8606, IRA contribution deadline, traditional IRA deduction limits, and Form 5498 box 1.
Sources
- Instructions for Form 8606, Nondeductible IRAs (2025): https://www.irs.gov/pub/irs-pdf/i8606.pdf
- Form 8606, Nondeductible IRAs (2025): https://www.irs.gov/pub/irs-pdf/f8606.pdf
Read from the IRS documents linked above on October 18, 2026. General information, not tax advice. Your own facts decide the outcome, and a preparer, the account provider or the IRS is the right place to confirm anything consequential.