Updated October 18, 2026. Quick answer: Line 2 is your total basis in traditional IRAs, the amount you carry in from earlier years. If this is the first year you must file Form 8606 it is usually zero. Otherwise the instructions send you to the Total Basis Chart, which points to a line on your last Form 8606.
IRS worksheets read line by line: Pub 590-B Worksheet 1-1.
What line 2 asks for
The form’s caption reads “Enter your total basis in traditional IRAs. See instructions”. Basis here is the after-tax money already in your traditional IRAs from earlier years. Line 1 covers this year’s nondeductible contributions on the Form 8606 line 1 page.
Where the number comes from
The instructions begin with “Generally, if this is the first year you are required to file Form 8606, enter-0-.” They continue: “Otherwise, use the Total Basis Chart to find the amount to enter on line 2.” The chart is a table in the instructions, headed by the year of the last Form 8606 you filed. Find that year on the chart and take the line it names, because the line differs by year.
The instructions then list when the chart answer needs adjusting: “you may need to enter an amount that is more than-0- (even if this is the first year you are required to file Form 8606) or increase or decrease the amount from the chart if your basis changed”. One cause is “You had a return of excess traditional IRA contributions”. Another is “Incident to divorce, you transferred or received part or all of a traditional IRA”. A third is “You rolled over any nontaxable portion of your qualified retirement plan to a traditional IRA that wasn’t previously reported on Form 8606, line 2.” For that last case, “Include the nontaxable portion on line 2.”
Where it goes next
Line 2 is added to line 1. The form says “Add lines 1 and 2”, on line 3. See the lines 3, 4 and 5 page. Your prior-year basis often traces to line 14 of last year’s form, covered on the lines 9 to 14 page. If the basis came from an inherited account, the inherited IRA basis page covers that situation.
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
- Entering zero when your basis changed. The instructions say you may need an amount that is more than zero, or an adjusted amount, if “You rolled over any nontaxable portion of your qualified retirement plan to a traditional IRA that wasn’t previously reported on Form 8606, line 2.”
- Guessing the carryover instead of using the chart. The instructions say “use the Total Basis Chart to find the amount to enter on line 2.”
- Ignoring a divorce transfer. The instructions list “Incident to divorce, you transferred or received part or all of a traditional IRA” as a reason to adjust.
Related: Form 8606, inherited IRA basis, backdoor Roth pro-rata calculator, 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.