How to File Your Equity Compensation Taxes: The Forms Guide

To file equity comp taxes, start with your W-2, which already includes RSU vesting and NSO exercise income. Report any share sales on Form 8949 and Schedule D, fixing the cost basis your broker understates. Use Form 3922 for ESPP basis and Form 6251 for AMT from ISO exercises.

Equity comp turns a simple return into a multi-form puzzle, and the pieces are easy to misfile — the most expensive mistake is paying tax twice on the same dollars. This guide maps every form your RSUs, ISOs, NSOs, and ESPP touch, in the order you'll use them, with the one basis adjustment that keeps you from overpaying. For the broader picture of how this income threads through your return, our overview of how equity compensation affects your tax return is a good companion read.

The Forms You Need to File Equity Comp Taxes by Type

The forms you file depend on what kind of equity you hold and whether you sold shares. Here's the map:

Two patterns fall out of the table. First, ordinary income almost always rides on your W-2 (RSU vests, NSO exercises, ESPP disqualifying dispositions). Second, every share sale flows through Form 8949 and Schedule D, regardless of equity type. The special forms — 6251 for ISO AMT, 3922 for ESPP — handle the cases the W-2 can't. For the difference between statutory and non-statutory options that drives this, see ISOs vs NSOs.

A quick way to think about it: ask two questions for each grant. Did I recognize income this year? If yes, it's almost certainly on the W-2 already (the ISO exercise-and-hold is the one exception — its "income" is AMT-only). Did I sell shares this year? If yes, you owe a Form 8949 entry, even if the gain is tiny or zero. Most equity-comp returns get complicated not because the rules are exotic, but because a single person can answer "yes" to both questions for two or three different grant types in the same year — an RSU vest, an ESPP purchase, and an ISO exercise can all land in one tax year and each routes to a slightly different combination of forms.

Start With Your W-2

Your W-2 is the anchor of an equity-comp return because it already includes most of your equity income as wages. When RSUs vest, the fair market value is included in Box 1 (IRS Publication 525); when you exercise NSOs, the spread is also Box 1 wages, often flagged in Box 12 with Code V.

The practical implication: don't re-enter that income anywhere else. It's already taxed as wages. The most common over-reporting error is treating the Box 14 RSU label as additional income — it isn't; it's already inside Box 1. Our walkthrough of how to read your RSU W-2 shows exactly which box holds what, and how RSUs are taxed covers the underlying rules.

The chart is a reminder of why the W-2 matters so much: the flat 22% withheld at vest usually trails your real marginal rate, so even though the income is reported correctly, the tax on it is often under-paid — a gap you'll settle when you file. This is the part that surprises people: nothing on the return is "wrong," yet you still owe, because reporting and withholding are two different things. The W-2 reports the full income honestly; it just didn't withhold enough against it. Reconciling that gap — and deciding whether to fix it with a bigger refund target or with estimated payments next year — is the real planning work of an equity-comp return.

Report Sales on Form 8949 and Schedule D

Any time you sell equity-comp shares, you report the sale on Form 8949, and the totals carry to Schedule D (IRS About Schedule D). This is where the single most expensive equity-comp filing error lives: the cost-basis trap.

Your broker's Form 1099-B frequently reports a cost basis that is too low — often just the discounted ESPP purchase price, or even $0 for RSU shares — because it doesn't know how much of your purchase was already taxed as W-2 income. File it unchanged and you pay capital-gains tax on income you already paid ordinary tax on. Per the IRS Instructions for Form 8949, the fix is to enter the reported basis in column (e), use code B in column (f), and adjust the gain in column (g).

The IRS instructions are explicit that you correct, rather than accept, a wrong basis:

"If the basis shown on Form 1099-B isn't correct ... report the basis shown on Form 1099-B in column (e), and enter an adjustment in column (g)."

— IRS Instructions for Form 8949

The correct basis is straightforward by type:

• RSU shares: basis = the vest-date fair market value (already on your W-2).
• NSO shares: basis = exercise-date FMV (strike + spread already taxed).
• ESPP shares: basis = purchase price + the discount already reported as ordinary income.

Here's the fix in dollars. Say 500 RSU shares vested at $80 (a $40,000 W-2 figure) and you sold them at $84 for $42,000. Your real gain is $2,000. If the 1099-B reports a $0 basis, it shows a $42,000 gain — and taxes $40,000 that was already taxed as wages. Entering the $0 in column (e), code B in column (f), and a −$40,000 adjustment in column (g) restores the true $2,000 gain. On a single overlooked lot, that adjustment is worth thousands; across several years of vests, it's the difference between a correct return and a serious overpayment.

The scenarios above show how the after-tax result changes with the timing of a sale — short-term versus long-term — which Schedule D sorts for you once Form 8949 reports each lot. Get the basis right and the rest is arithmetic.

ESPP and ISO Add Form 3922 and Form 6251

Two equity types bring an extra form. ESPP participants receive Form 3922 for the first transfer of shares bought under a Section 423 plan; per the IRS guidance on Form 3922, it reports the grant date, purchase date, fair market values, and price paid — exactly the numbers you need to compute basis and the qualifying/disqualifying split. For the full rules, see how ESPP taxes work.

ISO holders who exercised and held across year-end file Form 6251 for the alternative minimum tax, because the bargain element is an AMT preference item (IRS About Form 6251). The exercise produces no regular-tax line, but it can produce real AMT — our guide to Form 6251 walks the form line by line.

A subtlety worth flagging: an ISO has a different basis for regular tax and for AMT. For regular tax, your basis is what you paid (the strike). For AMT, your basis includes the bargain element you already reported on Form 6251. When you eventually sell, that dual basis means your AMT gain is smaller than your regular gain, which is part of how the AMT credit unwinds over time. Tax software handles this if you feed it the exercise details, but it's a frequent source of error when people file the sale years later and have forgotten the original exercise. Keep your exercise confirmations with your tax records so the basis is reconstructable.

If you sold ESPP shares, the same qualifying-versus-disqualifying split that sets your ordinary-income amount also determines whether any of the discount appears on your W-2 — a disqualifying disposition usually puts it there with withholding, while a qualifying disposition typically does not, leaving you to report it without anything prepaid.

How to File Equity Comp Taxes Step by Step

Work the forms in this order and the return assembles cleanly:

1. Enter your W-2. Wages, including RSU vests and NSO exercises, in Box 1.
2. Gather your 1099-Bs for every brokerage where you sold shares.
3. Build Form 8949 lot by lot, correcting any understated basis with code B.
4. Carry totals to Schedule D, which splits short-term from long-term.
5. Add Form 6251 if you exercised and held ISOs.
6. Use Form 3922 to set ESPP basis (kept with your records; not filed).
7. Check withholding versus liability — if the W-2 under-withheld your equity income, you may owe a balance and need quarterly estimated taxes going forward. Map your effective rate to size it.

Frequently Asked Questions

What tax forms do I need for equity compensation? Your W-2 (for vest and exercise income), Form 8949 plus Schedule D (for any share sales), Form 3922 (ESPP basis), and Form 6251 (AMT from ISO exercise-and-hold). You won't need all of them every year — the set depends on which equity types you hold and whether you sold shares.

Do I report RSUs on Form 8949? Only the sale of vested RSU shares. The vesting income itself is already on your W-2 and should not be re-entered.

Why is my 1099-B cost basis wrong? Brokers often report only what you paid, omitting the income already taxed on your W-2. Adjust the basis on Form 8949 with code B so the same dollars aren't taxed twice.

What form is ISO AMT reported on? Form 6251. The ISO bargain element on an exercise-and-hold is an AMT preference item even though it isn't on your regular return.

What is Form 3922 for? It reports the grant date, purchase date, fair market values, and price for ESPP shares — the inputs you need to compute basis and your qualifying-versus-disqualifying split at sale. You keep it with your records rather than filing it with your return.

Before You File

The biggest dollar swings in an equity-comp return come from getting basis right and not under-paying the withholding gap. Model your numbers first so the filing confirms what you already expect, rather than surprising you. Keep every vest statement, exercise confirmation, 1099-B, Form 3922, and prior-year Form 6251 in one place — most filing errors trace back to a missing document, not a misunderstood rule. None of this is individual tax advice; for a complex year, a qualified preparer who understands equity comp is well worth the fee.