Tax Form 1099-B: Boxes, Adjustments, and How to Report It

Form 1099-B is the tax document your broker or barter exchange sends to you and the IRS after you sell stocks, bonds, mutual funds, or other capital assets during the year.¹ It lists the proceeds from each sale, the cost basis when the broker has it, and whether the transaction produced a short-term or long-term result. You use those figures to fill out Form 8949 and Schedule D on your Form 1040. Because the IRS already has a copy, leaving anything off is one of the easier ways to trigger a matching notice.

What Gets Reported on the Form

A broker files a 1099-B for each customer whose stocks, bonds, mutual funds, ETFs, options, commodities, regulated futures, or other securities were sold for cash during the year.¹ Debt instrument redemptions and securities exchanged for other property also count. Corporate acquisitions and substantial changes in capital structure that leave you holding cash or new stock trigger a 1099-B too.

Barter exchanges use the same form to report the fair market value of what you received in a trade of services or property, and that value is taxable even though no cash moved.¹

Digital assets are moving off this form. Starting with the 2026 tax year, brokers handling cryptocurrency and other digital assets report those transactions on Form 1099-DA instead of 1099-B.² Digital assets acquired on or after January 1, 2026 that qualify as covered securities will have basis reported; anything acquired earlier may show proceeds only, so you’ll need your own records to establish basis.

Reading the Boxes That Matter

Each 1099-B covers a single transaction, or a summary of similar ones, and a handful of boxes do the real work when you file.³

Boxes 1b and 1c show the date you acquired the asset and the date you sold it. These set the holding period.
Box 1d is the total dollar proceeds from the sale, before adjustments.
Box 1e is the cost or other basis, adjusted for things like commissions or reinvested dividends. It’s only required for covered securities.
Box 1f reports accrued market discount on a bond bought below face value, which is taxed as ordinary income when you sell.
Box 1g shows adjustments, most commonly a disallowed wash-sale loss.
Box 2 marks the gain or loss as short-term, long-term, or ordinary.

Federal income tax withheld sometimes appears on the form as well. That’s backup withholding, usually triggered when the IRS told your broker your taxpayer identification number was wrong or you didn’t certify it.⁴ Report it on your return as federal tax paid so you get credit for it.

Covered vs. Non-Covered Securities

For covered securities, brokers must report cost basis to both you and the IRS.³ Coverage phased in over years: stocks acquired after 2010, mutual fund and ETF shares acquired after 2011, and most bonds acquired after 2014.

For non-covered securities, only the proceeds are reported. The basis is on you. Original trade confirmations, old account statements, and dividend reinvestment records are the usual sources. If you claim a basis the IRS can’t see on any form, expect a letter asking you to back it up.

When the Form Should Arrive

Brokers must furnish your 1099-B by February 15 of the year after the transactions. For 2026 sales, that’s February 15, 2027.⁵ Most brokerages post the form to your online account and may mail a paper copy. If yours hasn’t shown up by late February, contact the broker directly.

Brokers can request a 30-day extension, which pushes some forms into mid-March.⁶ If a corrected 1099-B arrives after you’ve already filed, you may need to file Form 1040-X to match the new figures.

Short-Term vs. Long-Term Treatment

Hold an asset one year or less and the gain is short-term. Hold it more than one year and it’s long-term.⁷ Short-term gains are taxed at ordinary income rates, topping out at 37% in 2026. Long-term gains get preferential rates of 0%, 15%, or 20% based on your taxable income.⁸

The 2026 brackets:

0% rate: taxable income up to $49,450 (single), $98,900 (married filing jointly), or $66,200 (head of household).
15% rate: income above those thresholds up to $545,500 (single), $613,700 (married filing jointly), or $579,600 (head of household).
20% rate: income above the 15% ceiling.

Higher earners owe an additional 3.8% Net Investment Income Tax on capital gains when modified adjusted gross income tops $200,000 (single) or $250,000 (married filing jointly).⁹ Stacked on top of the 20% bracket, the real ceiling on long-term gains is 23.8%.

Using Losses to Offset Gains

Capital losses offset capital gains dollar for dollar. If losses exceed gains, you can deduct up to $3,000 of the net loss against ordinary income, or $1,500 if married filing separately.⁸ Anything beyond that carries forward to future years indefinitely.

The carryforward is automatic in the sense that you’re entitled to it, but nobody tracks it for you. The IRS won’t remind you. Keep a copy of the Schedule D and Capital Loss Carryover Worksheet from the loss year so you can apply the balance next season.¹⁰

Adjustments You May Need to Make

Wash Sales

A wash sale occurs when you sell a security at a loss and buy a substantially identical one within 30 days before or after the sale. The IRS disallows the loss deduction.¹¹ The disallowed amount isn’t gone; it’s added to the basis of the replacement shares, deferring the benefit until you sell those without triggering another wash.

Your broker flags wash sales within your account and shows the disallowed amount in Box 1g. But brokers only see their own books. Sell at a loss with one broker and buy the same stock at another broker, or in your IRA, within 30 days, and it’s still a wash sale. Catching that is your job.

Inherited Stock

When you inherit securities, the basis generally steps up to the fair market value on the date of the original owner’s death. If a parent bought stock at $10 and it was worth $80 when they died, your basis is $80. That usually cuts the taxable gain substantially, sometimes producing a loss.

Brokers often don’t have the stepped-up figure. They may report the decedent’s original cost or leave basis blank. You have to establish the date-of-death value using estate records or historical prices, then adjust the basis on Form 8949 so your return reflects the correct number instead of the broker’s.

When the 1099-B Is Simply Wrong

Errors show up most often with non-covered basis, corporate actions like splits and mergers, and shares transferred between brokers. Ask the broker for a corrected form; they’re required to issue one and refile with the IRS.⁶

If a correction won’t come in time, file with the right numbers and document the fix on Form 8949. Column (f) has adjustment codes for exactly this. Enter the 1099-B figures in the proceeds and basis columns, then apply your adjustment with the code so the IRS can reconcile the gap without flagging the return.

Reporting a 1099-B on Your Tax Return

The path is 1099-B to Form 8949 to Schedule D to Form 1040.¹² On Form 8949, transactions are sorted by holding period and by whether basis was reported to the IRS.¹³

There’s a useful shortcut. If a transaction involves a covered security with basis reported to the IRS and needs no adjustments, you can skip Form 8949 and report the totals directly on Schedule D, line 1a for short-term or line 8a for long-term.¹² For a return with dozens of clean trades, that’s a real time saver on paper.

Form 8949 is still required for any transaction where basis wasn’t reported to the IRS, where you’re making an adjustment (wash sales, inherited stock, gifted property), or where you’re correcting a broker error. Totals flow from Form 8949 to Schedule D and then to Form 1040. Tax software handles the routing automatically, and most brokerages offer direct import so you don’t type in hundreds of trades.

For digital assets, keep detailed records of every purchase, transfer between wallets, and disposal, including timestamps and wallet addresses. The regulations require brokers to trace specific assets from acquisition to disposition within a particular wallet or account, and transfers between wallets or exchanges can complicate basis. The IRS now has the infrastructure to match those records against what you report.

Penalties If You Don’t Report

Because the IRS gets its own copy of every 1099-B, unreported sales are among the easiest items for the automated matching system to catch. If the omission leaves tax unpaid, a failure-to-pay penalty of 0.5% per month, up to 25% of the unpaid amount, starts running from the filing deadline.¹⁴

The IRS also lists failing to report 1099 income as an example of negligence that can trigger the accuracy-related penalty, which adds 20% of the underpayment on top of the tax owed.¹⁵ Interest compounds on the rest. Even if you can’t pay the full bill, reporting every transaction on the return removes the accuracy-penalty risk and shrinks the overall exposure.

1
Internal Revenue Service. About Form 1099-B, Proceeds from Broker and Barter Exchange Transactions
2
Internal Revenue Service. About Form 1099-DA, Digital Asset Proceeds From Broker Transactions
3
Internal Revenue Service. Instructions for Form 1099-B – Proceeds From Broker and Barter Exchange Transactions
4
Internal Revenue Service. Topic No. 307, Backup Withholding
5
Internal Revenue Service. Publication 1099 (2026), General Instructions for Certain Information Returns
6
Internal Revenue Service. General Instructions for Certain Information Returns (2025)
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Office of the Law Revision Counsel. 26 USC 1222 – Other Terms Relating to Capital Gains and Losses
8
Internal Revenue Service. Topic No. 409, Capital Gains and Losses
9
Internal Revenue Service. Topic No. 559, Net Investment Income Tax
10
Internal Revenue Service. Instructions for Schedule D (Form 1040)
11
Office of the Law Revision Counsel. 26 USC 1091 – Loss From Wash Sales of Stock or Securities
12
Internal Revenue Service. Instructions for Form 8949 – Sales and Other Dispositions of Capital Assets
13
Internal Revenue Service. Form 8949 – Sales and Other Dispositions of Capital Assets
14
Internal Revenue Service. Failure to Pay Penalty
15
Internal Revenue Service. Accuracy-Related Penalty