Why Your RSU Cost Basis Looks Wrong on Form 1099-B

You download your Form 1099-B from your brokerage account in February, scroll down to the sales of shares from your restricted stock units (RSUs), and stop in disbelief. Box 1d lists the gross proceeds from your sale, but Box 1e, which reports your cost basis, reads zero or sits completely blank. If you enter those figures into tax filing software without adjustments, the system calculates a capital gain on the full value of the sale, creating a substantial artificial tax liability.

Brokers often report a zero or missing cost basis on Form 1099-B because the broker reporting rules don't require them to include the income you were already taxed on at vesting, and many report RSU shares as noncovered securities (shares whose basis isn't reported to the IRS). When your RSUs vested, you already paid ordinary income tax on their fair market value through payroll withholding reported on your Form W-2. If you do not manually report your adjusted cost basis on Form 8949, you will pay tax on that exact same compensation income twice.

When managing high-value equity compensation, understanding how RSU withholding shortfalls work is critical during vesting, but correcting your cost basis at tax time is equally essential to protect your net worth.

Who This Applies To (and Who Can Disregard It)

This cost basis reporting problem applies directly to tech employees, engineering managers, and executives who sold shares acquired through vested restricted stock units. If you sold vested RSU shares through your company's stock plan broker, your Form 1099-B may not show your actual cost basis.

This issue does not apply to shares of common stock purchased directly on the open market through a brokerage account after 2011, which are classified as covered securities where brokers are legally mandated to track and report adjusted basis. It also operates differently for employee stock purchase plans (ESPPs), where qualifying and disqualifying dispositions require distinct calculation rules.

Why Brokers Report Zero Basis on Form 1099-B

The broker reporting rules don't require your broker to include the ordinary income you recognized at vesting in Box 1e of Form 1099-B, and many brokers report RSU shares as noncovered securities, meaning the basis isn't reported to the IRS.

As a result, custodians report your transaction under one of two default options: they either leave Box 1e entirely blank, or they enter $0.00, and Box 12 (checked only when basis is reported to the IRS) is left unchecked.

This regulatory disconnect does not mean you have a zero basis. Under federal tax law, your true cost basis equals the fair market value of the shares on the date they vested. Because that fair market value was already taxed as ordinary wage income on your Form W-2, that exact dollar amount becomes your tax basis for calculating capital gains or losses when you liquidate the stock.

The Mechanics of RSU Double Taxation

When your RSUs vest, your employer executes a sell-to-cover transaction, selling a portion of your shares automatically to cover statutory supplemental tax withholding. The remaining net shares are deposited directly into your brokerage account. Because that vesting event is fully taxable, those deposited shares enter your account with a built-in tax cost basis equal to the market price on the vest date.

If you subsequently sell those shares, your capital gain or loss should reflect only the change in share price between the vest date and the sale date. For example, if shares vest at $150 and you later sell them at $160, your true taxable capital gain is $10 per share. However, if your tax preparer or filing software accepts the broker Form 1099-B showing a $0 basis, the IRS calculates a capital gain on the full $160 sale price. You are taxed once on the initial $150 of value as ordinary income, and then taxed a second time on that same $150 as a capital gain.

In California, this error is particularly expensive. California does not offer a preferential tax rate for long-term capital gains, taxing all capital gains as ordinary income at rates reaching up to 12.3 percent, plus an additional 1 percent surcharge on taxable income over $1 million for a maximum combined rate of 13.3 percent. You can see the full schedule in our guide to California RSU tax rates. Furthermore, high-income filers subject to federal thresholds face an additional 3.8 percent net investment income tax on investment gains, compounding the cost of uncorrected double taxation.

How to Report the Adjusted Cost Basis on Form 8949

To prevent double taxation, you must report the transaction on IRS Form 8949 (Sales and Other Dispositions of Capital Assets) and transfer the summary totals to Schedule D. The process requires a disciplined order of operations:

1. Retrieve Your Broker Supplemental Information Statement

Do not rely exclusively on the Form 1099-B tax document. Most stock plan administrators provide a companion document titled Supplemental Information, Stock Plan Transaction Supplement, or RSU Cost Basis Statement. This document displays the vest date, number of shares sold, original fair market value at vest, and your adjusted cost basis.

2. Enter the Transaction Details on Form 8949

Record each sale on Form 8949. If you held the shares for one year or less after vesting, report the sale under Part I for short-term capital assets. If you held the shares for more than one year after vesting, report the sale under Part II for long-term capital assets. Because your broker did not report your basis to the IRS, select Box B (short-term) or Box E (long-term).

3. Record the Adjustment Code and Offset

In column (d), enter the gross sales proceeds matching Box 1d of your Form 1099-B. In column (e), enter your correct cost basis from the supplemental statement (the value of the shares at vest, already taxed on your W-2). In column (f), enter adjustment Code B, which tells the IRS the basis shown on Form 1099-B is incorrect. In column (g), enter zero. Column (h) then shows your actual capital gain or loss. If Box 12 on your 1099-B is checked, meaning the basis was reported to the IRS, the method differs: use Box A or Box D, enter the reported basis in column (e), and correct it with an adjustment in column (g).

Learning how to diversify RSUs without a tax hit requires this accounting discipline, ensuring you do not surrender valuable liquidity to avoidable compliance errors.

Strategic Questions to Bring to a Tax Strategist

Reconciling your RSU basis is the first step in a broader strategy for tech executives managing concentrated positions. As you plan future vests and sales, review these questions with an Enrolled Agent practice:

• If I failed to adjust my cost basis in prior tax years, can I file an amended return on Form 1040-X within the statutory three-year window to claim a refund?
• How do multi-year equity grants affect my overall tax profile, and how equity grants reshape your tax bracket across federal and state levels?
• How should I schedule share liquidations alongside year-round tax planning strategies to manage quarterly estimated tax payments and safe harbor rules?
• What are the state sourcing implications under California residency tax rules for equity if I move to a state like Texas or Florida after my shares vest?

If you hold concentrated equity or recently sold vested shares, the first step is a free 15-minute discovery call with our team. The paid strategy session that follows is where we review your equity grants, 1099-B statements, and overall tax picture. Call our San Diego office at (619) 280-2700 or email info@RoadmapTax.com.

For more on RSU tax planning, see Laid Off With Unvested RSUs: What to Review Before Your Last Day.

FAQ

Why does my broker report zero cost basis on Form 1099-B for my RSUs?

Broker reporting rules don't require brokers to add the income you were taxed on at vesting into Box 1e on Form 1099-B, and many report RSU shares as noncovered securities. Brokers often report zero or leave the box blank, requiring you to provide the adjusted cost basis on Form 8949.

What happens if I file my taxes without adjusting my RSU cost basis?

Filing without adjusting your basis causes the IRS to tax the entire gross sale proceeds as a capital gain. Because you already paid ordinary income tax on the fair market value at vest via your Form W-2, you end up paying tax on the same income twice.

Where do I find my real RSU cost basis?

Your true cost basis is listed on the supplemental equity reporting statement provided by your plan administrator, such as E*TRADE, Fidelity, or Charles Schwab. This document details the vest date, share count, and fair market value used for payroll tax calculations.

Can I amend a previous tax return if I accidentally paid tax twice on RSUs?

Yes, you can file an amended return using Form 1040-X to correct unadjusted RSU cost basis from prior tax years. Taxpayers generally have three years from the date they filed the original return or two years from the date they paid the tax, whichever is later, to claim a refund.

Are capital gains from RSU sales subject to the 3.8 percent net investment income tax?

Capital gains recognized when you sell shares above their vest date fair market value are subject to the 3.8 percent net investment income tax if your modified adjusted gross income exceeds statutory thresholds. However, the initial vest value taxed as wages is never subject to this tax.

This article is for educational purposes only and does not constitute tax, legal, or investment advice.