No, keep it for your records; only staple it to a mailed return when it shows federal tax withheld and you’re claiming that withholding.
A Form 1099-INT is a year-end report from a bank, credit union, broker, or agency that paid you interest. The IRS gets its own copy from the payer, so most taxpayers don’t mail their copy in. Your return just needs the totals in the right spots on Form 1040 and any schedules.
The one place people get tripped up is Box 4. If the form shows federal income tax withheld, you’re claiming a payment. When you mail a paper return, attaching the form that shows withholding helps the IRS post that payment without delays.
Attaching a 1099-INT to a Paper Tax Return: The practical rule
If you e-file, you do not attach the paper 1099-INT. You enter the figures in your software, and the IRS matches them to what the payer filed.
If you mail a paper return, you still usually do not attach the 1099-INT. Attach it only when Box 4 shows federal income tax withheld and you’re claiming that amount on your return. The Form 1040 instructions explain how withholding from Forms 1099 is reported on line 25b, including withholding tied to interest (Instructions for Form 1040 (2025)).
One more thing people mix up: Schedule B. If your taxable interest is more than $1,500, you list payers on Schedule B and attach that schedule to your return. That’s a schedule you complete, not the payer’s 1099-INT. The IRS spells out the Schedule B threshold in its interest FAQ (1099-INT interest income FAQ).
Where 1099-INT numbers go on your return
Treat the form like a checklist. Each filled-in box either becomes taxable income, a special type of interest, a tax payment, or a note to keep with your records. Most people only have Box 1 filled in, yet it’s smart to scan every box before you file.
Taxable interest and the Schedule B trigger
Box 1 is taxable interest. Add it to any other taxable interest you received, even if no form arrived. If your total taxable interest is more than $1,500, list each payer on Schedule B and attach it, per the IRS interest FAQ (1099-INT interest income FAQ).
If your taxable interest is $1,500 or less, you can often report it directly on Form 1040 without Schedule B, unless a Schedule B question applies to you for other reasons. Tax software routes this for you, though it helps to know what it’s asking.
Box 4 withholding changes your filing steps
Box 4 is federal income tax withheld. Publication 550 notes that Box 4 amounts are claimed on Form 1040 / 1040-SR line 25b (Publication 550 (2025)).
E-file: enter Box 4 in your software and keep the form.
Mail: enter Box 4 on line 25b, then attach the 1099-INT copy that shows the withholding near the front of the return packet.
Read the form like a mini-audit
Before you type anything into software, pause and sanity-check the form. Confirm your name and taxpayer ID. Then match the payer name to the account you expect. If you have multiple savings accounts, it’s easy to mix up which 1099 belongs to which account, especially when two banks merge or a brokerage rebrands.
Next, scan for boxes that change the tax treatment. Tax-exempt interest (often from municipal bond funds) is reported on the tax-exempt line on Form 1040, not mixed into taxable interest. Foreign tax in Box 6 can open a credit or deduction path, which is why brokerages often provide a separate year-end statement that backs up that number. Bond amortization or market discount boxes can also mean the payer already adjusted a figure, so you want the payer’s supplemental page saved with your tax records.
Finally, check for amounts that are easy to miss: an early withdrawal penalty in Box 2, or a small amount of withholding in Box 4. Those two boxes don’t change how much interest you earned, yet they can change your refund or balance due.
Common 1099-INT boxes and what to do with them
This table is a map from the form’s boxes to the actions they tend to trigger on a personal return.
| 1099-INT box | What it usually means | What you do |
|---|---|---|
| Box 1 | Taxable interest (bank interest, CD interest) | Report as taxable interest; use Schedule B if total taxable interest is over $1,500 |
| Box 2 | Early withdrawal penalty from a time deposit | Claim as an adjustment to income (your software places it) |
| Box 3 | Interest from U.S. savings bonds and Treasury obligations | Report as taxable interest; watch for special bond rules if you reported some interest in prior years |
| Box 4 | Federal income tax withheld (often backup withholding) | Claim on line 25b; attach the form if you mail a paper return |
| Box 6 | Foreign tax paid | May allow a foreign tax credit or deduction; keep fund statements that match it |
| Box 8 | Tax-exempt interest (often municipal bond funds) | Report as tax-exempt interest on Form 1040; it can still affect other calculations |
| Box 9 | Private activity bond interest | May relate to AMT; tax software asks follow-up questions |
| Box 10 | Market discount | Report based on your bond reporting method; keep the payer’s statement |
| Box 11–13 | Bond amortization details | May reduce reportable interest; follow the payer’s supplemental info and IRS instructions |
When to attach the 1099-INT to a mailed return
If Box 4 is blank, there’s no withholding payment to prove, so you normally don’t attach the form. If Box 4 has an amount, you’re claiming a payment on line 25b, and attaching the form helps the IRS verify that payment while processing.
How to attach it without creating a mess
- Attach only the 1099-INT forms that show federal withholding in Box 4.
- Place them behind Form 1040 page 1, near other withholding documents.
- Don’t attach extra correspondence unless the IRS instructions call for it (Instructions for Form 1040 (2025)).
Situations that can change what you do
Backup withholding and getting it stopped
Box 4 withholding often shows up as backup withholding. It can start when a payer doesn’t have your taxpayer ID on file, or the IRS tells the payer there’s a mismatch. You can usually stop it by giving the payer a correct Form W-9 or updated account details. For filing, the rule stays simple: claim the withholding on line 25b, attach the 1099-INT if you mail, keep the paperwork that shows you fixed the issue.
Corrected 1099-INT forms
If you get a corrected 1099-INT, use the corrected numbers. Keep both versions. If you mail a return and the corrected form shows Box 4 withholding, attach the corrected copy, not the earlier one.
Joint accounts and nominee interest
A joint account may issue one 1099-INT under the first SSN on file, even when two owners share the funds. Publication 550 explains nominee interest reporting when you’re listed on a 1099-INT that includes someone else’s share (Publication 550 (2025)).
If you’re passing part of the interest to another owner, your return still reports the full amount you received on the form, then removes the other person’s share as a nominee amount on Schedule B. The other owner reports their share on their return.
Refund interest from a state agency
Some states issue 1099-INT forms for refund interest. Treat it like any other 1099-INT: report the interest, and only attach the form if Box 4 shows federal withholding and you mail the return.
Attach or keep: A quick decision table
Use this as a last check before you click “submit” or seal the envelope.
| Situation | Attach to a mailed return | Keep in your records |
|---|---|---|
| E-file, any 1099-INT | Nothing from the payer | All 1099-INT forms and year-end statements |
| Mail return, Box 4 blank | No 1099-INT | All 1099-INT forms, plus any supplemental bond statements |
| Mail return, Box 4 has withholding | Attach the 1099-INT copy showing withholding | All 1099-INT forms and any payer notices tied to backup withholding |
| Corrected 1099-INT received | Attach only if the corrected copy has Box 4 withholding | Both original and corrected copies |
| Nominee interest on a joint account | No attachment unless your own 1099-INT has Box 4 withholding | Allocation notes and any nominee forms you issued or received |
| Foreign tax shown in Box 6 | Nothing extra with the 1099-INT | Fund tax reports and statements that match the foreign tax figure |
Paper filing tips that save you from IRS mail
These small checks can prevent mismatches and processing delays.
- Match your totals. If you’re claiming withholding from more than one 1099, make sure line 25b equals the sum of every Box 4 amount you’re claiming.
- Report every payer’s interest. The IRS matches payer filings to your return, so missing a small 1099-INT can trigger a mismatch notice.
- Keep a clean folder. Save each 1099-INT, the year-end statement, and any add-on pages that explain bond amortization, market discount, or foreign tax.
What to do if you never received a 1099-INT
First, check your account’s online tax documents. If you can’t get the form, you can still report interest using statements. Publication 550 notes you must report taxable interest even if you don’t receive a 1099-INT (Publication 550 (2025)).
If you think Box 4 withholding existed, don’t guess. Claim withholding only when you can document it.
Final checklist
- All taxable interest totals are on Form 1040, and Schedule B is attached when required.
- Any Box 4 withholding is included on line 25b.
- If you’re mailing and Box 4 withholding exists, the 1099-INT copy showing withholding is attached near the front.
If those points line up, you’ve handled the form the way the IRS expects.
References & Sources
- Internal Revenue Service (IRS).“Instructions for Form 1040 (2025).”Explains how to report federal withholding from Forms 1099 on line 25b and gives paper return attachment guidance.
- Internal Revenue Service (IRS).“1099-INT interest income.”States when Schedule B is required and summarizes reporting steps for interest income.
- Internal Revenue Service (IRS).“Publication 550 (2025), Investment Income and Expenses.”Details treatment of Box 4 withholding and nominee interest reporting rules.
- Internal Revenue Service (IRS).“About Form 1099-INT, Interest Income.”Overview of what Form 1099-INT reports and who files it with the IRS.