Updated October 17, 2026. Quick answer: Box 4 of Form RRB-1099 shows the SSEB portion of tier 1 benefits you repaid to the Railroad Retirement Board during the year, and box 5 shows the net amount paid. Publication 915 says box 5 is the result of subtracting box 4 from box 3. Box 5 is the figure the taxability test starts from, and parentheses around it mean you repaid more than you received.
Read box by box from the IRS form text: Form RRB-1099-R boxes 5 and 6 and Form RRB-1099-R boxes 7 to 12.
What box 4 reports
The publication describes the box this way: “The figure shown in this box is the total SSEB portion of tier 1 benefits you repaid to the RRB in 2025.” The gross amount you were paid sits in box 3, which is explained on the box 3 page. Box 4 is its counterpart for money that went back.
This page covers boxes 4 and 5 together because box 5 is calculated from them. The rest of the form is mapped in the SSA-1099 and RRB-1099 boxes guide.
How a repayment arises
The publication lists several ways an amount ends up in box 4.
| How a repayment arises | What Publication 915 says |
|---|---|
| You returned a payment, made a cash refund, or had an amount withheld | “You may have repaid a benefit by returning a payment, making a cash refund, or having an amount withheld from your payments.” |
| Someone else on your claim number was overpaid | “an amount may have been withheld from your benefits to recover the SSEB overpayment incurred by someone else who is also receiving benefits under your claim number” |
| The RRB recovered an overpayment from another benefit | “an amount may have been withheld from another benefit, such as a social security benefit, to recover an SSEB overpayment you received” |
| The repayment was for an earlier year | “The amount in box 4 also includes any SSEB benefits you repaid in 2025 that were for 2025 or for 1 or more years before 2025.” |
Notice that a repayment does not have to be money you wrote a check for. Withholding from your own payments counts, and so does an amount withheld from another benefit, such as a social security benefit.
Example 1: returning to work for the railroad
The first example in the publication: “Because you aren’t allowed to receive benefits for any month you returned to railroad service, you have to make a repayment to the RRB.” “Box 4 of your Form RRB-1099 will show $1,350 ($450 × 3 months) as the SSEB portion of tier 1 benefits you repaid to the RRB.”
Example 2: an overpayment recovered by withholding
The second example: “From May through August 2025, $200 a month was withheld from your benefit payment to fully recover the $800 overpayment.” “Box 4 of your Form RRB-1099 will show $800 ($200 × 4 months) as the SSEB portion of tier 1 benefits you repaid to the RRB.”
Example 3: a social security benefit kept by the RRB
The third example involves both forms. “Social security benefits of $900 ($300 × 3 months) covering the period May through July 2025 were kept by the RRB to offset your $900 SSEB overpayment for that same period.” “Box 4 of your Form RRB-1099 will show $900 as the SSEB portion of tier 1 benefits you repaid to the RRB.” The publication adds a note about the other form: “SSA will provide Form SSA-1099, which will include the $900 in benefits paid by SSA for the months of May through July 2025.” The SSA-1099 side is read on the SSA-1099 box 5 page.
What box 5 reports and how it is calculated
Box 5 is the net figure: “The figure shown in this box is the net amount of the SSEB portion of tier 1 benefits paid to you in 2025.” “It is the result of subtracting the amount in box 4 from the amount in box 3.” Because the publication states that relationship for this form, the subtraction is safe to use for a quick check of your own form.
As an illustration, not an IRS example: if box 3 showed $12,000 and box 4 showed $1,350 then box 5 would show $12,000 minus $1,350 = $10,650. The second illustration is the negative case: if box 3 showed $1,000 and box 4 showed $1,500 then the result is $1,000 minus $1,500 = negative $500 and the form would print it in parentheses.
More than one form, and a negative box 5
Some people hold several forms. “If you received more than one Form RRB-1099 for 2025, you should add the amounts in box 5 of all Forms RRB-1099 to determine your net amount of SSEB payments for 2025.” “Use this amount to determine if any of your benefits are taxable.”
Parentheses matter: “If parentheses are around the figure in box 5, it means that the figure in box 4 is larger than the figure in box 3.” “This is a negative figure and means you repaid more money than you received in 2025.” The publication’s section on that situation says: “your net benefits in box 5 will be a negative figure (a figure in parentheses) and none of your benefits will be taxable”. “If you receive more than one form, a negative figure in box 5 of one form is used to offset a positive figure in box 5 of another form for that same year.”
The publication’s worksheets carry this warning: “Don’t use this worksheet if you repaid benefits in 2025 and your total repayments (box 4 of Forms SSA-1099 and RRB-1099) were more than your gross benefits for 2025 (box 3 of Forms SSA-1099 and RRB-1099).” The publication covers a repayment larger than gross benefits under the heading “Repayments More Than Gross Benefits”. See also Form 1040 for the return and the social security tax torpedo page for how the rest of your income interacts with benefits.
Edition and box numbers
The primary read for this page is Publication 915, Social Security and Equivalent Railroad Retirement Benefits, the version written for 2025 returns, and its Appendix section on Form RRB-1099 that prints the 2025 form. The publication states its scope this way: “This section explains the items shown on Form RRB-1099.” irs.gov was serving that version at its current publication address on 2026-10-17. No other edition of the publication was compared for this page, so nothing here is a statement about a later tax year. Box 4 and box 5 carry the form year in their labels, for example repaid in 2025; the sample form in the publication shows 2025. The publication also advises: “You should, however, compare the form you received with the one shown in this publication to note any differences.” Check the tax year printed on the form you received before relying on the box numbers and years described here.
Common mistakes
- Using box 3 alone when you repaid benefits. The publication says box 5 is “the result of subtracting the amount in box 4 from the amount in box 3”.
- Adding only one form’s box 5 when you have several. The instruction is to “add the amounts in box 5 of all Forms RRB-1099”.
- Reading a figure in parentheses as a positive number. Parentheses mean “the figure in box 4 is larger than the figure in box 3”.
Related: Form 1040, Schedule A (Form 1040), the social security tax torpedo, and railroad retirement tier 1 and tier 2 taxation.
Sources
- Publication 915, Social Security and Equivalent Railroad Retirement Benefits (for 2025 returns): https://www.irs.gov/pub/irs-pdf/p915.pdf
- IRS web edition of Publication 915 (2025): https://www.irs.gov/publications/p915
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.