Form 3922 Cost Basis: ESPP Calculation and 8949 Adjustment

To calculate your Form 3922 cost basis, take the exercise price you paid (Box 5) and add the portion of your ESPP discount that gets taxed as ordinary income. The size of that add-back depends on how long you held the shares before selling. If you skip the adjustment and file with the basis your broker reports, you pay capital gains tax on income that already showed up as wages on your W-2.

The Five Boxes on Form 3922 That Drive the Math

Form 3922 records a single event: the purchase of stock through a Section 423 Employee Stock Purchase Plan at a price below fair market value.¹ You don’t attach it to a return. You keep it, because when you eventually sell those shares the boxes below are what you use to reconstruct the correct basis.²

Box 1, Grant Date: The day the offering period began. One of the two dates that decides whether your sale qualifies for favorable treatment.
Box 3, Fair Market Value on the Grant Date: The stock price on the grant date. This anchors the statutory cap on ordinary income for qualifying dispositions.
Box 4, Fair Market Value on the Exercise Date: The stock price the day the shares were purchased. Compared to Box 5, this is the actual discount you received.
Box 5, Exercise Price Paid: What came out of your paycheck per share. This is your starting basis before any adjustment. Under Section 423, this can be as low as 85% of the lower of the Box 3 or Box 4 values.³
Box 7, Date Legal Title Transferred: When the shares became yours. The one-year holding clock runs from this date. In many plans Box 7 matches or nearly matches the exercise date.

Box 6 gives the share count. Box 8 only comes into play when the exercise price wasn’t fixed or determinable on the grant date, which is unusual.

Qualifying or Disqualifying: The Question That Picks Your Formula

Before you touch the numbers, figure out which kind of sale you have. A qualifying disposition requires both of the following at the time of sale:³

More than two years from the grant date in Box 1.
More than one year from the transfer date in Box 7.

Miss either one and the sale is disqualifying. Both dates have to clear. Note that a disqualifying disposition can still produce a long-term capital gain if you held longer than a year from transfer but under two years from grant. Long-term for capital gains purposes is not the same test as qualifying for ESPP purposes.

Disqualifying Disposition: Basis Equals Box 4

The disqualifying formula is the simpler one. Your ordinary income is the full spread between the exercise-date fair market value and what you paid:

Ordinary income = Box 4 − Box 5

That amount goes into your compensation income for the year of the sale, regardless of what the stock did afterward. Your adjusted cost basis is your purchase price plus that ordinary income, which in effect resets the basis to Box 4:

Adjusted basis = Box 5 + (Box 4 − Box 5) = Box 4

Worked example. You paid $85 per share (Box 5) when the stock was worth $100 (Box 4). The $15 spread is ordinary income. Your adjusted basis is $100. Sell at $110, and you have a $10 capital gain on top of the $15 wage income. Sell at $92, and you still recognize $15 of ordinary income and take an $8 capital loss.

Qualifying Disposition: Ordinary Income Is Capped

For qualifying dispositions, Section 423(c) caps the ordinary income portion. It’s the lesser of two figures:³

The actual gain: sale price minus Box 5.
The grant-date discount: Box 3 minus Box 5.

Everything above that ordinary income amount is long-term capital gain. The grant-date discount cap is what makes qualifying dispositions worth waiting for. If the stock has doubled since the grant date, most of your profit falls into the capital gains bucket rather than ordinary income.

Your adjusted basis is the exercise price plus whichever of those two amounts was smaller.

Worked example. Grant-date FMV (Box 3) was $90 and you paid $76.50 (Box 5), a 15% discount off the grant-date price. You sell at $100.

Actual gain: $100 − $76.50 = $23.50
Grant-date discount: $90 − $76.50 = $13.50
Ordinary income (lesser): $13.50
Adjusted basis: $76.50 + $13.50 = $90.00
Long-term capital gain: $100 − $90 = $10.00

Not every plan discounts 15%. Section 423 allows anywhere from 0% to 15%, and the actual number sits in your plan documents. Plans with a lookback provision use the lower of the grant-date or exercise-date price as the discount base, which can make the effective discount larger when the stock rose during the offering period.

When the Sale Is at a Loss

Sell a qualifying disposition below your purchase price and the ordinary income piece is zero. The lesser-of test can’t go negative. Your basis stays at Box 5, and the entire shortfall is a long-term capital loss. Paid $76.50 and sold at $70? Basis is $76.50, loss is $6.50 per share.

Disqualifying dispositions at a loss are harsher. The ordinary income is still the full Box 4 minus Box 5 spread, because that got locked in on the day you bought. Your basis rises to Box 4, and the drop from Box 4 to the sale price is a capital loss. You end up reporting ordinary income and a capital loss on the same shares. The loss can offset other capital gains or up to $3,000 of ordinary income per year, but it does not erase the wage income already recognized.

Adjusting the Broker’s Basis on Form 8949

Your Form 1099-B almost certainly reports only Box 5 as the cost basis, without the ordinary income adjustment. Filing that number as-is means paying capital gains tax on dollars already taxed as wages. The correction happens on Form 8949.⁴

Check Box A or Box D at the top of the form if the broker reported basis to the IRS (short-term or long-term respectively). Check Box B or E if not. Your 1099-B tells you which.
Column (d): sale proceeds from the 1099-B.
Column (e): the basis the broker reported, even though you know it’s low.
Column (f): code B for a basis correction.
Column (g): the adjustment as a negative number equal to the ordinary income you added to Box 5. This reduces the reportable gain.

Totals from Form 8949 carry to Schedule D.⁵ Before filing, check that the ordinary income you calculated matches what your employer added to Box 1 of your W-2. Discrepancies invite IRS notices, because the agency already has your Form 3922 on file and can compare.

If You Can’t Find Your Form 3922

You can rebuild the five key figures from other sources. Broker confirmation statements and supplemental tax documents typically show the grant date, exercise date, both fair market values, and your purchase price. Many brokerages package this as a supplemental information statement alongside the 1099-B. You can also request a copy from your employer’s stock plan administrator or the transfer agent that handles the plan. Because the employer filed the form with the IRS, the data exists; the task is retrieval, which gets harder if you’ve since left the company.

A Warning About Withholding

Employers are not required to withhold federal income tax on the ordinary income from an ESPP disposition, and Social Security and Medicare taxes don’t apply to it. The income lands on your W-2, but no cash was set aside to pay the tax. If you sold a meaningful position, the gap between your withholding and what you owe can be large. The safe harbor from underpayment penalties is generally 90% of the current year’s tax or 100% of the prior year’s tax, rising to 110% if your adjusted gross income was over $150,000.⁶ If you sell mid-year, raising your W-4 withholding or making an estimated payment for the quarter of the sale keeps you inside that safe harbor.

1
Internal Revenue Service. About Form 3922, Transfer of Stock Acquired Through An Employee Stock Purchase Plan Under Section 423(c)
2
Internal Revenue Service. Instructions for Forms 3921 and 3922
3
Office of the Law Revision Counsel. 26 USC 423 – Employee Stock Purchase Plans
4
Internal Revenue Service. Instructions for Form 8949 (2025)
5
Internal Revenue Service. Stocks (Options, Splits, Traders) 5
6
Internal Revenue Service. Underpayment of Estimated Tax by Individuals Penalty