Form 1099-B: How Broker Sales Get Reported

Key Takeaways

• Form 1099-B reports proceeds from selling securities and, for covered lots, your cost basis.
• A covered security generally means stock bought after 2010, with basis reported to the IRS.
• Investors often assume the gain is calculated for them, but they must reconcile each sale.
• The form feeds Form 8949 and Schedule D, where short-term and long-term gains are taxed differently.

What Form 1099-B Is

Form 1099-B, titled Proceeds From Broker and Barter Exchange Transactions, is an information return. Your broker files it with the IRS and sends you a copy reporting each sale or exchange of securities, commodities, options, and similar property during the year.

The form reports gross proceeds in box 1d and, for covered securities, the adjusted cost basis in box 1e. It also flags whether the gain is short-term or long-term and whether basis was reported to the IRS. The legal basis is Internal Revenue Code section 6045, which requires brokers to report customer transactions.

The Intuition

When you sell an investment, you owe tax on the gain, which is the sale price minus what you paid. The IRS cannot calculate that without knowing both numbers, so it requires brokers to report sales.

Before 2011, brokers reported only the proceeds, leaving taxpayers to supply cost basis on their own, which led to widespread errors. Congress phased in basis reporting, creating the idea of a "covered security." For covered lots the broker reports both proceeds and basis, which makes your gain easy to verify and harder to misstate.

How It Works

The boxes that matter most are:

Box 1a  Description of property
Box 1b  Date acquired
Box 1c  Date sold or disposed
Box 1d  Proceeds
Box 1e  Cost or other basis
Box 1f  Accrued market discount
Box 1g  Wash sale loss disallowed
Box 2   Short-term or long-term, and ordinary flag

A covered security generally includes stock acquired after 2010, or after 2011 for mutual fund shares and shares bought through a dividend reinvestment plan. For covered lots, box 1e shows basis that was also reported to the IRS. For noncovered lots, basis may be blank, and you must supply it yourself.

The gain or loss is proceeds in box 1d minus basis in box 1e, adjusted for items such as wash sales in box 1g. Box 2 tells you whether the holding period was short-term, taxed at ordinary rates, or long-term, taxed at lower rates.

Worked Example

Suppose you sold 100 shares of a stock you bought two years ago. Your broker reports:

Box 1d  Proceeds          = 9,500
Box 1e  Cost basis        = 7,000
Box 2   Long-term, basis reported to IRS

Your gain is 9,500 minus 7,000, or 2,500 dollars, taxed at long-term capital gains rates. Because basis was reported and there are no adjustments, you may be able to report this directly on Schedule D without listing it on Form 8949. If box 1g showed a wash sale adjustment, you would carry the detail to Form 8949 and adjust the loss accordingly.

Common Mistakes

1. Assuming the tax is already figured. The form reports proceeds and basis, but you compute and report the gain. Skipping that step can trigger a mismatch notice.

2. Ignoring noncovered lots. When box 1e is blank, the broker did not report basis. You must supply your own records, or the IRS may treat the entire proceeds as gain.

3. Mishandling wash sales. A wash sale loss in box 1g is disallowed for now and added to the basis of the replacement shares. Forgetting this overstates a current loss.

4. Overlooking accrued market discount. Box 1f can convert part of a bond gain into ordinary income. Treating it all as capital gain misstates the tax.

5. Missing the short versus long-term split. Box 2 sets the holding period. Lumping everything together can apply the wrong rate and inflate your bill.

Frequently Asked Questions

What is Form 1099-B in simple terms? Form 1099-B is a tax form your broker sends that lists the securities you sold during the year, along with the proceeds and usually your cost basis. It is the starting point for figuring your capital gains tax.

How does Form 1099-B affect investment decisions? Because the form separates short-term from long-term gains, it shows the tax cost of selling, which can favor holding past the one-year mark for the lower rate. Reviewing realized gains late in the year also guides tax-loss harvesting.

What is a real-world example of Form 1099-B? If you sell 100 shares for 9,500 dollars that cost you 7,000 dollars, the broker reports both numbers, and you report the 2,500 dollar gain on your return.

How can investors avoid errors with Form 1099-B? Reconcile every line against your own records, supply basis for any noncovered lots, and apply wash sale and market discount adjustments before filing. Keeping confirmations for each purchase makes basis easy to defend.

How is Form 1099-B different from Form 1099-DIV? Form 1099-B reports gains from selling investments, while Form 1099-DIV reports dividends and distributions from holding them. One covers what you sold, the other what you collected while holding.

Sources

1. IRS. "Instructions for Form 1099-B (2026)." https://www.irs.gov/instructions/i1099b
2. IRS. "About Form 1099-B, Proceeds From Broker and Barter Exchange Transactions." https://www.irs.gov/forms-pubs/about-form-1099-b
3. IRS. "Instructions for Form 8949 (2025)." https://www.irs.gov/instructions/i8949
4. Cornell Legal Information Institute. "26 U.S.C. 6045 - Returns of brokers." https://www.law.cornell.edu/uscode/text/26/6045

Disclaimer

This article is educational content only and is not financial advice. Nothing here is a recommendation to buy, sell, or hold any security. Consult a licensed advisor before making investment decisions.