Updated October 17, 2026. Quick answer: Box 2b of Form 1099-R holds two checkboxes. For the first, the recipient instructions say the payer was unable to determine the taxable amount, that box 2a should be blank except for a traditional IRA or traditional SIMPLE IRA, and that it is your responsibility to determine the taxable amount. For the second, they say the distribution was a total distribution that closed out your account.
Two checkboxes in one box
The caption on the form reads “Taxable amount not determined” beside a second box labelled “Total distribution”. The recipient instructions describe each: “If the first box is checked, the payer was unable to determine the taxable amount” and “If the second box is checked, the distribution was a total distribution that closed out your account.” The full form is laid out on Form 1099-R boxes explained.
The first checkbox: taxable amount not determined
The recipient instructions continue: “box 2a should be blank, except for a traditional IRA or traditional SIMPLE IRA.” The next sentence reads “It’s your responsibility to determine the taxable amount.” The payer’s instructions give the reason a payer checks it: “if you are unable to reasonably obtain the data needed to compute the taxable amount.” And they give the matching entry rule: “If you check this box, leave box 2a blank”. The box 2a page is the companion: box 2a.
The payer’s instructions also say how hard the payer should try: “Except for traditional IRAs, make every effort to compute the taxable amount.” If an entry on your form looks wrong, see the what to do when a 1099-R is wrong page.
Why traditional IRAs are different
The recipient instructions say for a traditional IRA “generally the payer isn’t required to compute the taxable amount.” The payer’s instructions spell out how that appears on the form: “report the total amount distributed from a traditional IRA in box 2a.” In the same entry the payer is told “Check the “Taxable amount not determined” box in box 2b.” The basis form, Form 8606, has its own page.
The payer’s instructions also say “A conversion is considered a distribution and must be reported even if it is with the same trustee”. The same entry says “Check the “Taxable amount not determined” box in box 2b.” Roth conversions are covered on the Roth conversion taxes page.
The second checkbox: total distribution
The payer’s instructions define the term: “A total distribution is one or more distributions within 1 tax year in which the entire balance of the account is distributed.” And they say when to mark it: “in this box only if the payment shown in box 1 is a total distribution.” The instruction for installments reads “If periodic or installment payments are made, mark this box in the year the final payment is made.”
Total distributions and Form 4972
The recipient instructions tie a total distribution to a possible special rule: “If this is a total distribution from a qualified plan and you were born before January 2, 1936” (or you are the beneficiary of someone born before that date), “you may be eligible for the 10-year tax option.” The paragraph points to the Form 4972 instructions for the details. The capital gain side of that same paragraph is on the box 3 page.
More of the payer’s text for box 2b
The payer’s entry rule for the first box reads “Enter an “X” in this box if you are unable to reasonably obtain the data needed to compute the taxable amount.” The entry then adds a second case: “In addition, enter an “X” in this box if you are an FFI reporting in box 1 to satisfy your chapter 4 reporting requirement under the election described in Regulations section 1.1471-4(d)(5)(i)(B).” It goes on to say “If you check this box, leave box 2a blank; but see Traditional IRA, earlier.”
For a traditional IRA the payer’s instructions begin “Generally, you are not required to compute the taxable amount of a traditional IRA or designate whether any part of a distribution is a return of basis attributable to nondeductible contributions.” A separate bullet in that entry covers excess contributions: “For a distribution of excess contributions without earnings after the due date of the individual’s return under section 408(d)(5), leave box 2a blank, and check the “Taxable amount not determined” box in box 2b.”
For the second box the payer’s entry opens with “Enter an “X” in this box only if the payment shown in box 1 is a total distribution.” The entry then gives the definition and the installment rule quoted above.
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Related pages
Box 1 is covered on the box 1 page and the box 7 codes on the box 7 codes page. Required minimum distributions are covered on the required minimum distributions page.
Edition and box numbers
The primary read for this page is the 2025 Form 1099-R with its 2025 filer instructions. The 2026 edition was the current one irs.gov served on 2026-10-17. In the 2026 form the recipient paragraph for box 2b says “If the first box is checked, the payer was unable to determine the taxable amount” and ends with “If the second box is checked, the distribution was a total distribution that closed out your account.” The 2026 filer instructions add Trump account text under box 2b. For the total distribution box it says “Distribution of excess contributions from a Trump account. Do not enter an “X” in this box.” and for the ABLE rollover case it says “Distribution for a qualified ABLE rollover contribution. Enter an “X” in this box.” Check the tax year printed on the form you received. The neighbouring boxes are on the box 2a page and the overview is Form 1099-R boxes explained.
Common mistakes
- Treating a checked first box as a mistake on the form. The instructions say “the payer was unable to determine the taxable amount” and also “It’s your responsibility to determine the taxable amount.”
- Waiting for the payer to compute a traditional IRA’s taxable amount. The instructions say “generally the payer isn’t required to compute the taxable amount.”
- Expecting the total distribution box to be checked on every payment. The instructions say “If periodic or installment payments are made, mark this box in the year the final payment is made.”
Related: Form 8606, Roth conversion taxes, 1099-R box 7 codes, Required minimum distributions, and What to do when a 1099-R is wrong.
Sources
- Form 1099-R (2025) with Instructions for Recipient: IRS archived PDF (irs.gov)
- Form 1099-R (2026) with Instructions for Recipient: https://www.irs.gov/pub/irs-pdf/f1099r.pdf
- 2025 Instructions for Forms 1099-R and 5498: IRS archived PDF (irs.gov)
- 2026 Instructions for Forms 1099-R and 5498: https://www.irs.gov/pub/irs-pdf/i1099r.pdf
Read from the IRS documents linked above on October 17, 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.