ESPP Disqualifying Disposition Cost Basis: How to Fix the Form 8949 Adjustment.

A senior engineer at a Bay Area tech company sells 625 ESPP shares eight months after purchase, locks in what looks like a clean short-term gain, and her preparer hands back a return that taxes the same dollars twice. The 1099-B from the broker shows cost basis of $21,250. Her W-2 already includes $10,000 of extra ordinary income from those same shares. Without a Form 8949 adjustment, that $10,000 hits the return a second time as capital gain. The ESPP disqualifying disposition cost basis problem is the most common preparation error I see on tech-employee returns, and the fix is one column on one form.

IRC §423 gives an employee stock purchase plan favorable tax treatment if the holding period is satisfied. The qualifying-disposition test is more than two years from the offering date and more than one year from the purchase date, and the two thresholds run independently. Anything shorter is a disqualifying disposition under §423(c). For employees buying at a 15% discount with a six-month lookback, the temptation to sell into a run-up is high, and disqualifying dispositions are the rule rather than the exception.

On a disqualifying disposition, the bargain element becomes ordinary compensation income equal to the FMV at the purchase date minus the actual purchase price. The number lands on Form W-2 Box 1, and most employers also disclose it in Box 14 with a label like ESPP or DDQDIS. It is not subject to Social Security or Medicare withholding because IRC §3121(a)(22) and IRS Notice 2002-47 exclude statutory option and ESPP compensation from FICA wages. The ordinary income piece is already taxed by the time the employee files. The trap is that the same dollars show up a second time when the shares are sold.

For shares acquired on or after January 1, 2014, brokers report cost basis to the IRS on Form 1099-B under the broker-reporting regime in IRC §6045(g). Treasury Regulation §1.6045-1 governs the calculation, and the rule for compensatory stock prohibits the broker from increasing basis to include the compensation income recognized at acquisition. The broker reports what the employee paid, the discounted purchase price, and not the FMV at purchase that becomes the true tax basis once the bargain element is added. Importing the 1099-B straight into TurboTax or any other software without an override puts the wrong basis on the return. The bargain element gets taxed once as ordinary income on the W-2 and a second time as short-term capital gain on Schedule D.

The correction goes on Form 8949. ESPP shares acquired after 2014 and sold through a broker are covered securities, so the sale lands on Box A (short-term covered) or Box D (long-term covered) depending on the holding period from the purchase date. In column (e), enter the broker-reported basis from the 1099-B. In column (f), enter adjustment code B, which the Form 8949 instructions describe as the entry for a return where the basis shown on the 1099-B in box 1e is incorrect. In column (g), enter the bargain element as a negative number. The gain in column (h) is proceeds minus broker basis plus the column (g) adjustment, and that negative entry is what avoids the double tax.

The bargain element to add to basis is the same number that lands on the W-2. If Box 14 does not disclose it cleanly, Form 3922 does. Under IRC §6039, the employer must furnish Form 3922 to every employee who acquires shares under a §423 ESPP, with the FMV at offering, the FMV at purchase, the actual price paid, and the number of shares transferred. The bargain element on a disqualifying disposition is the FMV at purchase minus the price paid, multiplied by the shares sold, and Form 3922 has to be in the employee's hands by January 31 of the year following the transfer.

A qualifying disposition has its own ordinary-income calculation that the broker also leaves out of basis. Under §423(c), the ordinary income on a qualifying disposition is the lesser of (a) the discount the employee could have realized at the offering date, computed as FMV at offering minus the price the option would have purchased the stock for at offering, or (b) the actual gain on sale. For shares that appreciated through the offering period, the offering-date discount usually controls and the ordinary income is much smaller than in a disqualifying disposition. The employer is not required to add this income to the W-2, FICA does not apply, and the employee reports it on Form 1040 line 1h as other earned income. The Form 8949 fix is the same: code B, negative column (g) equal to the ordinary income piece, and the gain in column (h) becomes long-term capital gain.

For the larger equity-compensation problems, like the California trailing tax on RSUs after a move out of state or the new tiered structure of the Washington capital gains tax on RSU sales, the cost basis mechanics are downstream of the bigger sourcing and rate questions. The ESPP basis fix is a smaller-dollar issue, but it is also one of the easiest to leave on the table because the broker's report looks complete on its face.

If a prior return picked up the broker basis without the adjustment, the refund claim goes on Form 1040-X under IRC §6511, three years from the original due date or two years from payment, whichever is later. The 2022 return amendment window closed April 15, 2026, so for ESPP disqualifying dispositions reported on the 2022 Form 1040, the door is shut. Tax year 2023 returns can still be amended until April 15, 2027, and 2024 and 2025 returns have longer runways. Most missed adjustments I unwind on amendment trace back to a self-prepared return where the 1099-B imported into the software without an override and the Box 14 disclosure on the W-2 was either ignored or read as a duplicate of the same wages.