Executive Summary
How do I report equity compensation on my 2025 tax return?
Each equity type follows a specific reporting path: RSU income appears on your W-2 and requires a cost basis adjustment on Form 8949/Schedule D when you sell shares. ISO exercises trigger AMT reporting on Form 6251 using Form 3921 data. ESPP sales need a basis correction on Form 8949 using Form 3922. NSO exercise income flows through your W-2 and into Form 8949 when shares are sold. In all cases, your broker's 1099-B likely understates cost basis—you must correct it.
Every year, billions of dollars in equity compensation are reported incorrectly on tax returns. The core problem is deceptively simple: your broker, your employer, and the IRS each see only part of the picture. Your 1099-B shows a sale. Your W-2 shows income. Form 3921 or 3922 shows the grant-level details. It falls on you to stitch these documents together into a coherent, accurate return—or face double taxation, underpayment penalties, or an IRS notice.
The bottom line: If you received equity compensation in 2025, you almost certainly need to adjust the cost basis reported on your 1099-B before entering it on Form 8949. Failing to do so is the single most expensive mistake equity-compensated employees make at tax time.1
Critical Warning: Brokers are only required to report the price you paid for shares—not the income you already recognized on your W-2. For RSUs with no purchase price, the 1099-B may show a cost basis of zero. For ESPPs, it shows the discounted purchase price without the W-2 adjustment. If you file using the 1099-B numbers as-is, you will pay tax twice on the same income.2
Related Guides: For deep dives on each equity type, see our RSU Tax Guide, ISO vs NSO comparison, ESPP Taxation Guide, and Forms 3921/3922/W-2 Explained. For wash sale complications, see our Wash Sale Rules guide.
Gather Your Documents: The Equity Tax Filing Toolkit
Before you open your tax software or sit down with your CPA, collect every document related to your equity compensation. Missing even one form can lead to incorrect basis calculations or omitted income.
Documents You Need by Equity Type
| Document | RSUs | ISOs | NSOs | ESPPs | What It Tells You |
|---|---|---|---|---|---|
| W-2 (Boxes 1, 12, 14) | Yes | Maybe | Yes | Maybe | Ordinary income recognized from equity events |
| 1099-B | Yes (if sold) | Yes (if sold) | Yes (if sold) | Yes (if sold) | Sale proceeds and broker-reported cost basis |
| Form 3921 | No | Yes | No | No | ISO exercise details (grant date, exercise date, FMV, strike price) |
| Form 3922 | No | No | No | Yes | ESPP purchase details (offering date, purchase date, FMV, purchase price) |
| Form 6251 | No | Yes (if exercised) | No | No | AMT calculation for ISO bargain element |
| Equity plan statements | Yes | Yes | Yes | Yes | Vesting dates, lot-level detail, supplemental basis info |
Where to Find Key W-2 Codes
Your W-2 contains equity-related information in specific boxes:3
| W-2 Location | Code | What It Reports |
|---|---|---|
| Box 1 | — | Total wages including all equity income (RSU vesting, NSO exercise spread, disqualifying ESPP/ISO dispositions) |
| Box 12, Code V | V | Income from NSO exercises (included in Box 1) |
| Box 14 | Varies | Employer-specific equity detail (e.g., "RSU," "ESPP," "ISO DQ") — informational only |
| Boxes 3-6 | — | Social Security and Medicare wages — equity income subject to FICA |
Tip: Box 12 Code V for NSOs and the Box 14 notations are your reconciliation anchors. Cross-reference these amounts against your brokerage statements to ensure every dollar of equity income is accounted for exactly once—not zero times, not twice.
Reporting RSUs: The Basis Adjustment That Saves Thousands
RSU taxation is straightforward in concept but error-prone in execution. When RSUs vest, the fair market value of the shares is reported as ordinary income on your W-2. If you later sell those shares, you must report the sale on Form 8949 and Schedule D.4
The Problem: Your 1099-B Is Wrong
Most brokers report your RSU cost basis as zero or very low on Form 1099-B because your "purchase price" was effectively nothing. But you already paid tax on the full FMV at vesting through your W-2. Without a basis adjustment, the IRS sees a sale with nearly 100% profit—income you already paid tax on.
Step-by-Step RSU Reporting
- Find your W-2 income. Locate the RSU vesting income in Box 1 (and often Box 14). This is your tax basis per share (FMV on vesting date multiplied by shares vested).
- Check your 1099-B. Look at Box 1e (cost basis). If it shows zero or a number that does not include the W-2 income, you need to adjust.
- Complete Form 8949. Enter the sale in Part I (short-term) or Part II (long-term) depending on your holding period from the vesting date.
Form 8949 Entry for RSUs
| Column | What to Enter | Example |
|---|---|---|
| (a) Description | Company stock — RSU | 100 sh XYZ Corp (RSU) |
| (b) Date acquired | Vesting date | 03/15/2025 |
| (c) Date sold | Sale date | 09/20/2025 |
| (d) Proceeds | From 1099-B Box 1d | 15,000 |
| (e) Cost basis | From 1099-B Box 1e | 0 (broker-reported) |
| (f) Code | B (basis reported to IRS is incorrect) | B |
| (g) Adjustment | Add W-2 income as basis | 12,000 |
| (h) Gain or loss | (d) minus (e) minus (g) | 3,000 |
Code B in column (f) tells the IRS you are correcting the cost basis. The adjustment in column (g) equals the ordinary income already reported on your W-2 for those specific shares.
For more on RSU taxation mechanics, see our comprehensive RSU tax guide.
Reporting ISOs: Form 3921, AMT, and Holding Periods
Incentive Stock Options have the most complex reporting requirements of any equity type. The tax treatment depends entirely on whether you make a qualifying disposition (favorable capital gains treatment) or a disqualifying disposition (ordinary income treatment).5
Qualifying vs. Disqualifying: The Holding Period Test
| Requirement | Qualifying Disposition | Disqualifying Disposition |
|---|---|---|
| Hold from grant date | 2+ years | Fewer than 2 years |
| Hold from exercise date | 1+ year | Fewer than 1 year |
| Tax on spread at exercise | AMT only (Form 6251) | Ordinary income (W-2) |
| Tax on sale gain | Long-term capital gains | Capital gains on remainder |
Step-by-Step ISO Reporting
At Exercise (no sale):
- Retrieve Form 3921 from your employer. It shows the grant date (Box 1), exercise date (Box 2), exercise price per share (Box 3), FMV per share on exercise date (Box 4), and number of shares (Box 5).
- Calculate the bargain element: (Box 4 FMV minus Box 3 exercise price) multiplied by Box 5 shares. This is your AMT adjustment.
- Complete Form 6251. Enter the bargain element on Line 2i. Work through the form to determine whether you owe AMT.
- No Form 8949 entry yet—you have not sold the shares.
At Sale (qualifying disposition):
- Report the sale on Form 8949, Part II (long-term).
- Date acquired = exercise date. Date sold = sale date. Proceeds = sale price. Cost basis = exercise price (strike price paid).
- The entire gain is long-term capital gains. No W-2 income.
- If you paid AMT in a prior year, claim the AMT credit on Form 8801.
At Sale (disqualifying disposition):
- The spread at exercise (FMV minus strike price) becomes ordinary income on your W-2.
- Report the sale on Form 8949 with basis = exercise price + W-2 income (to avoid double counting).
- Use Code B for the basis adjustment, just like RSUs.
- Any additional gain above exercise-date FMV is capital gains.
AMT Form 6251: Key Lines for ISO Exercises
| Form 6251 Line | Description | Source |
|---|---|---|
| Line 1 | Taxable income from Form 1040 | Form 1040, Line 15 |
| Line 2i | ISO adjustment (bargain element) | Form 3921: (Box 4 − Box 3) × Box 5 |
| Line 7 | Alternative minimum taxable income | Sum of adjustments |
| Line 9 | AMT exemption (2025: 88,100 single / 137,000 MFJ) | IRS annual amounts |
| Line 11 | AMT tax rate (26% / 28%) | Applied to excess over exemption |
For a deeper dive on AMT planning, see our AMT planning guide. For the full ISO vs. NSO comparison, see our ISO vs NSO guide.
Reporting ESPPs: Form 3922 and the Double-Tax Trap
ESPP shares are the most commonly mis-reported equity type because the cost basis on your 1099-B almost never reflects the income you already recognized. The adjustment depends on whether your sale is a qualifying or disqualifying disposition.6
ESPP Holding Period Rules
| Disposition Type | Offering Date Holding | Purchase Date Holding | Income Treatment |
|---|---|---|---|
| Qualifying | 2+ years from offering date | 1+ year from purchase date | Ordinary income = lesser of (a) actual gain or (b) purchase discount. Remainder = LTCG |
| Disqualifying | Fewer than 2 years | OR fewer than 1 year | Ordinary income = full spread at purchase (FMV minus price paid). Remainder = capital gain/loss |
Step-by-Step ESPP Reporting
- Retrieve Form 3922. Key boxes: offering date (Box 1), date shares transferred/purchased (Box 7), FMV on offering date (Box 4), FMV on purchase date (Box 5), purchase price per share (Box 3), and number of shares (Box 8).
- Determine disposition type. Compare your sale date against the two holding periods.
- Calculate ordinary income:
- Qualifying: Lesser of (sale price minus purchase price) or (offering-date FMV multiplied by discount percentage). This amount should appear on your W-2.
- Disqualifying: Purchase-date FMV minus purchase price paid, multiplied by shares. This appears on your W-2.
- Adjust cost basis on Form 8949. Your correct basis = purchase price + ordinary income recognized on W-2.
- Use Code B in column (f) to flag the basis correction.
Why does my ESPP 1099-B show the wrong cost basis?
Your broker reports only the discounted purchase price you actually paid — it does not include the ordinary income portion reported on your W-2. You must add the W-2 income to the 1099-B basis on Form 8949 (using Code B) to arrive at the correct adjusted basis. Without this step, you pay tax twice on the discount.
For the full ESPP taxation breakdown, see our ESPP taxation guide.
Reporting NSOs: W-2 Box 12 Code V and Form 8949
Non-Qualified Stock Options have simpler reporting than ISOs but still require careful basis tracking when you sell the acquired shares.
How NSO Income Flows Through Your Return
- At exercise: The spread (FMV minus strike price) is ordinary income. It appears on your W-2 in Box 1 and is flagged in Box 12 with Code V. FICA taxes (Social Security and Medicare) apply.
- At sale: Report on Form 8949. Your cost basis = strike price + ordinary income from W-2 (the exercise-date FMV). This prevents double counting.
Form 8949 Entry for NSO Shares
| Column | What to Enter | Example |
|---|---|---|
| (a) Description | Company stock — NSO exercise | 500 sh XYZ Corp (NSO) |
| (b) Date acquired | Exercise date | 06/01/2025 |
| (c) Date sold | Sale date | 12/15/2025 |
| (d) Proceeds | Sale price from 1099-B | 75,000 |
| (e) Cost basis | Broker-reported (often strike price only) | 25,000 |
| (f) Code | B (if basis does not include W-2 income) | B |
| (g) Adjustment | W-2 income from exercise spread | 25,000 |
| (h) Gain or loss | 75,000 − 25,000 − 25,000 | 25,000 |
If you did a same-day sale (cashless exercise), there may be no additional gain to report—but you still need to verify that the 1099-B basis matches the FMV at exercise. Discrepancies are common.
The Five Costliest Reporting Mistakes (and How to Fix Them)
Mistake 1: Double-Counting Equity Income
What happens: You file using the 1099-B as-is without adjusting the cost basis. The IRS sees massive capital gains that overlap with the ordinary income already on your W-2. Result: you pay tax twice on the same dollars.
The fix: Always compare your 1099-B cost basis against your W-2 equity income. Add the W-2 amount to the reported basis on Form 8949 using Code B.
Mistake 2: Using the Wrong Holding Period Start Date
| Equity Type | Holding Period Starts | Common Error |
|---|---|---|
| RSUs | Vesting date | Using grant date (too early → incorrectly claims LTCG) |
| ISOs | Exercise date | Using grant date |
| ESPPs | Purchase date (for capital gains); offering date also matters for disposition type | Using enrollment date |
| NSOs | Exercise date | Using grant date |
The fix: Your holding period for capital gains purposes starts when you receive (or are deemed to receive) the shares—not when the grant was made.
Mistake 3: Ignoring AMT on ISO Exercises
What happens: You exercise ISOs and hold the shares past year-end without filing Form 6251. The IRS sends a notice for unpaid AMT plus penalties.
The fix: Every ISO exercise that is held past December 31 requires an AMT calculation on Form 6251, even if you ultimately owe no additional AMT. Use Form 3921 data for the bargain element calculation.
Mistake 4: Missing Multi-State Allocations
What happens: If you moved states or worked remotely in multiple states during the vesting or exercise period, the equity income must be allocated among those states. Many filers report 100% to their current state of residence, triggering audit risk in the state where the income was partly earned.
The fix: Allocate equity income based on working days in each state during the relevant period (grant-to-vest for RSUs, grant-to-exercise for options). File non-resident returns where required. For details, see our guide on multi-state tax for remote workers.
Mistake 5: Forgetting Wash Sale Adjustments on Equity Shares
What happens: You sell equity shares at a loss and receive new shares from an RSU vest or ESPP purchase within 30 days. The wash sale rule disallows the loss and adds it to the basis of the new shares. Many filers claim the loss without adjustment.
The fix: Track the 61-day window (30 days before and after each loss sale) for any substantially identical share acquisitions, including involuntary ones like RSU vests. See our wash sale rules guide for the full framework.
Tax Reporting Checklists by Equity Type
RSU Checklist
- Confirm W-2 Box 1 includes RSU vesting income
- Check W-2 Box 14 for RSU-specific notation
- Compare 1099-B cost basis against per-share FMV on vesting date
- If basis is zero or understated, use Form 8949 Code B to adjust
- Determine holding period: vesting date to sale date
- Report on Schedule D (short-term Part I or long-term Part II)
- Verify no wash sale triggered by nearby RSU vests
ISO Checklist
- Collect Form 3921 for every ISO exercise in 2025
- If shares held past 12/31/2025: complete Form 6251 for AMT
- Calculate bargain element: (FMV at exercise minus strike price) times shares
- If sold as qualifying disposition: report on Form 8949 Part II with exercise price as basis
- If sold as disqualifying disposition: check W-2 for ordinary income and adjust basis on Form 8949
- Track AMT credit carryforward on Form 8801 for future years
ESPP Checklist
- Collect Form 3922 for every ESPP purchase in 2025
- Determine qualifying vs. disqualifying disposition using both holding periods
- Calculate ordinary income component and verify it matches W-2
- Adjust 1099-B cost basis on Form 8949 using Code B
- Report correct capital gain or loss on Schedule D
- Retain Form 3922 and purchase confirmations for 7+ years
NSO Checklist
- Verify W-2 Box 12 Code V matches your calculated exercise spread
- Confirm 1099-B cost basis includes the exercise-date FMV (not just strike price)
- If basis is understated, adjust on Form 8949 with Code B
- Holding period starts on exercise date—classify gain as short-term or long-term accordingly
- If same-day sale: verify zero or minimal gain/loss after basis adjustment
Frequently Asked Questions
Q1: My 1099-B shows a cost basis of zero for my RSU shares. Is that an error?
Not technically an error by the broker—they are only required to report the amount you paid, which for RSUs is nothing. However, your actual tax basis is the FMV on the vesting date (the amount already taxed on your W-2). You must correct this on Form 8949 using adjustment Code B. Without this correction, you will be double-taxed.
Source: IRS Instructions for Form 8949
Q2: Do I need to file Form 6251 even if I do not owe AMT?
Yes, if you exercised ISOs during the tax year and held the shares past December 31. The form is used to calculate whether you owe AMT. Even if the result is zero AMT due, the IRS expects the form to be filed. Skipping it can delay processing or trigger a notice.
Source: IRS Form 6251 Instructions
Q3: What is Form 8949 Code B, and when do I use it?
Code B means "the basis reported to the IRS on your 1099-B is incorrect and you are providing the correct adjusted basis." You use it whenever your equity compensation shares have a 1099-B cost basis that does not include the ordinary income you recognized on your W-2. This applies to RSUs, ESPPs, disqualifying ISO dispositions, and NSOs when the broker did not adjust basis.
Source: IRS Instructions for Form 8949
Q4: I exercised ISOs and sold the shares in the same year. Do I still need to worry about AMT?
If you exercised and sold in the same calendar year in a disqualifying disposition, the bargain element is taxed as ordinary income on your W-2 instead of triggering AMT. In this case, you generally do not need to make an AMT adjustment on Form 6251 for those specific shares. However, if you exercised some ISOs and held them past year-end while selling others, you need Form 6251 for the held shares.
Source: IRC Section 422, IRS Publication 525
Q5: How do I know if my ESPP sale is a qualifying or disqualifying disposition?
Check two dates from your Form 3922: the offering date (Box 1) and the purchase/transfer date (Box 7). A qualifying disposition requires that you sold the shares more than 2 years after the offering date AND more than 1 year after the purchase date. If either condition is not met, it is a disqualifying disposition.
Source: IRS Form 3922 Instructions, IRC Section 423
Q6: Can my tax software handle all these equity adjustments automatically?
Most consumer tax software (TurboTax, H&R Block, FreeTaxUSA) can import your 1099-B, but they cannot automatically adjust basis for equity compensation. You must manually enter the Code B adjustment on Form 8949. Some premium tiers walk you through the process, but you still need your W-2, Form 3921, or Form 3922 data on hand to calculate the correct amounts.
Source: IRS Publication 525
What if I received an IRS notice saying I underreported capital gains?
This is common when the IRS matches your 1099-B (showing large proceeds with zero basis) against your return. Respond with a letter or Form 8949 showing the correct adjusted basis, including a copy of your W-2 proving the ordinary income was already reported. In most cases, the notice is resolved without additional tax owed. Respond within 30 days to avoid penalties.
Footnotes
Disclaimer: This guide discusses legal tax optimization strategies only. Tax evasion is illegal and is never recommended. This content is for educational purposes and does not constitute tax, legal, or financial advice. Tax laws vary by jurisdiction and change frequently. Always consult a qualified tax professional (CPA, tax attorney, enrolled agent) before making decisions based on this information. The authors accept no liability for actions taken based on this content.
Last Updated: March 9, 2026 Research Team: VestingStrategy Editorial Team
Primary Sources
| Source | Type | URL |
|---|---|---|
| IRS Publication 525 | Official Guidance | irs.gov/publications/p525 |
| IRS Instructions for Form 8949 | Official Instructions | irs.gov/instructions/i8949 |
| IRS Form 6251 Instructions | Official Instructions | irs.gov/pub/irs-pdf/i6251.pdf |
| IRS Form 3921 Instructions | Official Instructions | irs.gov/pub/irs-pdf/i3921.pdf |
| IRS Form 3922 Instructions | Official Instructions | irs.gov/pub/irs-pdf/i3922.pdf |
| IRC Section 422 | Statute | law.cornell.edu/uscode/text/26/422 |
| IRC Section 423 | Statute | law.cornell.edu/uscode/text/26/423 |
| IRS Publication 550 | Official Guidance | irs.gov/publications/p550 |
| Treasury Regulation § 1.83-1 | Regulation | law.cornell.edu/cfr/text/26/1.83-1 |
Footnotes
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IRS Publication 525 establishes that employers must report equity compensation income on Form W-2 and that this income constitutes the employee's cost basis in the acquired shares for purposes of calculating gain or loss on subsequent sale. ↩
-
IRS Instructions for Form 1099-B require brokers to report cost basis for covered securities, but basis for equity compensation shares often excludes the compensation element recognized by the employee, necessitating manual adjustment on Form 8949. ↩
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IRS Instructions for Form W-2 specify that NSO exercise income is reported using Box 12 Code V and that all equity compensation income included in Box 1 is subject to income tax withholding. ↩
-
Treasury Regulation Section 1.83-1(b) provides that the basis of property transferred in connection with services equals the amount paid plus the amount included in gross income. ↩
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IRC Section 422(a) establishes the qualifying disposition holding periods for ISOs: two years from grant date and one year from exercise date, with failure to meet either resulting in a disqualifying disposition. ↩
-
IRC Section 423(a) requires both the two-year offering-date and one-year purchase-date holding periods for ESPP qualifying disposition treatment, with the ordinary income component calculated differently for each disposition type. ↩