AMT Tax Planning: ISO Exercises, Phantom Income, and the Credit You Can Recover

Here is how AMT surprises Bay Area tech workers every year. You exercise 10,000 incentive stock options. Your strike price is $2. The latest 409A valuation puts the stock at $9. You made $70,000 in paper profit. You paid nothing for it yet because you have not sold the stock. In April, your CPA tells you that you owe $19,600 in alternative minimum tax on income you never received as cash. The company has not gone public. There is no liquidity. But the IRS wants a check.

This is not a rare edge case. This is the standard AMT story for tens of thousands of Bay Area startup employees every year. The alternative minimum tax system was designed in 1969 to make sure high-income taxpayers could not zero out their tax liability through preferences and deductions. ISO exercises became collateral damage. Understanding how AMT works, how to model it before you exercise, and how to recover the AMT credit in future years is one of the highest-value planning conversations a Bay Area tech worker can have with a CPA.

Silicon Valley Tax specializes in ISO AMT planning for startup employees, pre-IPO company workers, and established tech executives throughout the Bay Area. Our office is at 2051 Junction Ave, San Jose. Call (408) 383-9870 or book a free consultation to talk through your specific situation before your next exercise.

How the Alternative Minimum Tax Works (IRC Sections 55 Through 59)

The AMT is a parallel tax system that runs alongside the regular tax system. Every year you compute your tax twice: once under the regular rules and once under the AMT rules. You pay whichever amount is higher.

Under IRC Section 55, the AMT is imposed at two rates: 26% on the first $232,600 of alternative minimum taxable income (AMTI) above the exemption amount, and 28% on AMTI above that threshold (2025 figures for married filing jointly). The exemption itself is $137,000 for married filing jointly in 2025 and phases out at $5 for every $10 of AMTI above $1,237,450. At high income levels the exemption is fully phased out, meaning the full 26%/28% rate applies from the first dollar of AMTI.

IRC Section 56 and IRC Section 57 define the adjustments and preferences that go into AMTI. The ISO exercise spread is an AMT preference item under Section 56(b)(3). When you exercise an ISO and the fair market value exceeds your exercise price, that spread is added back to your income for AMT purposes. The critical distinction: for regular federal income tax, the ISO exercise is not a taxable event. For AMT, it is as if you received ordinary income on the exercise date.

IRC Section 59 covers the AMT credit and other special rules. The AMT credit (Form 8801) is the mechanism that prevents double taxation over time by allowing you to recover AMT paid on timing differences like ISO exercises.

ISO Exercises: The Primary AMT Trigger for Bay Area Tech Workers

Incentive stock options are governed by IRC Section 422. The key statutory benefit is that you do not recognize ordinary income when you exercise an ISO, and if you hold the shares for the required holding period (more than two years from grant and more than one year from exercise), your eventual gain on sale is long-term capital gain.

That benefit is real. But IRC Section 56(b)(3) claws it back for AMT purposes by treating the ISO spread as an AMT adjustment. So you get the federal income tax deferral at the cost of the AMT hit in the exercise year.

The Anatomy of an AMT Bill on an ISO Exercise

Consider a Bay Area engineer at a Series C startup with the following facts:

• W-2 income: $240,000
• RSU vest income already included in W-2: $45,000
• ISO exercise: 20,000 shares, strike price $1.50, current 409A FMV $8.00
• AMT preference item from ISO: 20,000 x ($8.00 - $1.50) = $130,000
• Married filing jointly, two children

Under the regular tax system, taxable income is approximately $240,000 (assuming standard deductions and the RSU already in W-2). Regular tax is roughly $42,800 after credits. No ISO exercise income shows up here.

Under the AMT system, AMTI is $240,000 plus $130,000 ISO preference minus the $137,000 exemption (partially phased out at this income level, let's say it reduces to $112,000) = $258,000 of AMTI. AMT on $232,600 at 26% = $60,476. AMT on the remaining $25,400 at 28% = $7,112. Total tentative minimum tax: $67,588. Less regular tax credit: $42,800. Net AMT owed: $24,788.

That $24,788 is a check due April 15, arising from 20,000 shares that have not been sold and for which there may be no current liquidity market. This is not a theoretical risk. This is a recurring April situation for Bay Area startup employees who exercised options the prior year without modeling the AMT first.

California AMT: What Happened and What Remains

California repealed its individual alternative minimum tax for tax years beginning on or after January 1, 2000. So California does not add a second layer of AMT on top of the federal AMT. Bay Area tech workers do not owe California AMT. That is the good news.

The complicated news is that California does not conform to the federal ISO tax treatment. For federal regular tax, an ISO exercise is not a taxable event. California does not follow this rule. California treats the ISO spread as ordinary income at exercise, just like a nonqualified stock option (NSO). The spread is subject to California income tax at up to 13.3% in the year of exercise, and your employer should withhold California income tax accordingly.

The California tax creates a compensating deduction when you later sell the shares: your California basis is the FMV at exercise, while your federal basis is the strike price (or the FMV if you paid AMT). This basis difference must be tracked and reconciled on Schedule D each year. It is one of the most common errors we find on self-prepared or under-specialized returns.

AMT Timing Strategies for Bay Area Tech Employees

The single most powerful AMT planning tool is timing. The AMT is computed at the end of each calendar year based on that year's income and preferences. By controlling when you exercise ISOs, you can manage the AMT exposure across multiple years rather than concentrating it in a single large hit.

Strategy 1: Exercise in Low-Income Years

The AMT exposure on an ISO exercise is determined partly by your other income. If you have a year with lower W-2 income, no bonus, no RSU vest events, or a year with large itemized deductions, your regular tax liability drops, which means the gap between your regular tax and your tentative minimum tax is smaller. A smaller gap means less incremental AMT from the ISO exercise.

Common low-income windows for Bay Area tech workers:

• The year you leave a job and your next W-2 starts partway through
• A year you take unpaid leave or a sabbatical
• A year when your RSU vesting cliff has not hit yet
• A year with large charitable deductions that reduce regular income (though note that charitable deductions do not reduce AMTI directly)

Strategy 2: Early Exercise Plus Section 83(b) Election

For startup employees with ISOs at an early-stage company, exercising shortly after grant when the 409A valuation is at or near the strike price eliminates the AMT preference item because the spread is zero or close to zero. The Section 83(b) election (filed within 30 days of exercise) locks in that low FMV as your federal and California tax basis.

This strategy works best when:

• The company has a recent 409A valuation near the strike price (ideally within the last 12 months)
• You have reasonable confidence the company will survive and grow
• The total exercise cost is manageable relative to your cash position
• You have at least 12 months before a likely liquidity event, since you need to hold for one year from exercise to get long-term capital gain treatment on sale

The 30-day deadline on the Section 83(b) election is absolute and has no exceptions. Miss it, and the election option is gone permanently. We build the election filing into our engagement workflow for early exercise clients.

Strategy 3: Spread ISO Exercises Across December and January

Each calendar year resets your AMT calculation. If you have a large number of ISOs you want to exercise and the total spread would create an unacceptably large AMT hit in a single year, splitting the exercise across year-end can distribute the AMT exposure across two tax years. Exercise a portion in late December and the remainder in early January. The spread from each batch goes into a different tax year's AMTI computation.

This requires advance planning because the December portion must settle before December 31. We model the December-January split routinely for clients with large ISO positions approaching a liquidity event.

Strategy 4: Disqualifying Dispositions as a Pressure Valve

If you exercised ISOs in a prior year and paid AMT, you may be able to reduce your AMT credit carryforward recovery timeline by triggering a disqualifying disposition. Selling ISO shares within two years of grant or within one year of exercise converts what would have been long-term capital gain into ordinary income, which eliminates the AMT preference item retroactively for that exercise. The trade-off: you lose the preferential capital gain treatment. We model both paths and present the after-tax numbers before recommending either.

The AMT Credit Carryforward: Getting Your Money Back

The AMT credit (Form 8801, Minimum Tax Credit) is one of the most misunderstood concepts in the ISO planning space. Here is the core mechanic.

When you pay AMT due to a timing difference like an ISO exercise, the IRS effectively recognizes that you have prepaid tax on income that will eventually be taxed again at regular rates when you sell the stock. To prevent permanent double taxation, you accumulate an AMT credit equal to the AMT attributable to timing differences. In future years when your regular tax liability exceeds your tentative minimum tax, the AMT credit offsets your regular tax dollar for dollar.

Example: In 2025 you pay $25,000 of AMT on ISO exercises. That $25,000 becomes an AMT credit on Form 8801. In 2026, your regular tax is $80,000 and your tentative minimum tax is $55,000. The $25,000 excess of regular tax over AMT can absorb $25,000 of your credit, reducing your 2026 regular tax bill by $25,000.

The credit fully recovers over time if:

1. Your regular tax consistently exceeds your tentative minimum tax in future years
2. You do not generate large additional AMT preferences in those years that keep your tentative minimum tax elevated

The credit recovery can stall if you continue exercising ISOs in subsequent years, keeping your tentative minimum tax high. We model the credit absorption forecast across a rolling 5-year window for clients with large AMT credit carryforwards.

When the Company Goes Public: AMT Planning Around IPOs and Tender Offers

The most consequential AMT planning situation in the Bay Area is the pre-IPO exercise decision. As a company approaches an IPO, the 409A valuation rises sharply. The window between the last pre-IPO 409A and the actual IPO price is often where the largest AMT exposures originate.

Pre-IPO exercise decisions involve several competing factors:

• AMT exposure at current 409A. How much AMT would you owe if you exercised now versus at IPO price?
• Lockup period. After IPO, most employees are locked up for 180 days. You cannot sell to pay the AMT bill until lockup expires, but the AMT is due April 15 of the year following exercise.
• Qualified small business stock (QSBS). Shares acquired by exercising ISOs in a C corporation that meets the Section 1202 criteria may qualify for the QSBS exclusion, which can exclude up to $10 million of gain from federal tax. Early exercise before the company is too large to qualify is time-sensitive.
• Company-sponsored tender offers. Some pre-IPO companies offer secondary liquidity through tender offers. The tax treatment of tender offer sales depends on whether you meet the ISO holding periods.

We work through the IPO exercise analysis with clients 6 to 12 months before a projected offering. The planning timeline matters because many of the best strategies require action well before the S-1 is filed.

Worked Example: Managing AMT Across Two Tax Years

Client profile (composite, anonymized). David, 34, senior engineer at a San Jose-based SaaS company that recently closed a Series D at a $600 million valuation. He has 50,000 vested ISOs with a strike price of $0.80. The current 409A valuation is $7.40. The company is targeting an IPO in 18 to 24 months. David's W-2 income is $280,000. Married, filing jointly. Spouse income $85,000.

The AMT exposure if he exercises all 50,000 ISOs in one year:

• ISO spread: 50,000 x ($7.40 - $0.80) = $330,000
• Total AMTI (roughly): $365,000 + $330,000 = $695,000, minus reduced exemption
• Estimated AMT: approximately $91,000
• Less estimated regular tax: approximately $86,000
• Incremental AMT owed: approximately $5,000 (because regular tax is close to AMT in this income range)

Wait, that sounds small. The reason is that David's high W-2 income means his regular tax is already high, so the gap between regular tax and tentative minimum tax is modest. This is actually a good year to exercise a large block because the incremental AMT cost is low. We ran the projection, confirmed the $5,000 incremental AMT, and David exercised 40,000 ISOs in November, keeping the remaining 10,000 for January to manage cash flow. He filed a Section 83(b) election for the unvested portion of the early exercise tranche.

Result: David now holds 40,000 ISO shares with a cost basis of $0.80, a California basis of $7.40, and a one-year holding clock running. At IPO, if the stock is at $22, his federal long-term capital gain is $22 - $0.80 = $21.20 per share on 40,000 shares = $848,000, taxed at 20% federal rate = $169,600. His AMT credit carryforward from the $5,000 AMT paid will offset future regular tax. Had he waited and exercised at $22 IPO price, the ISO spread alone would have been $21.20 x 40,000 = $848,000 in AMT preferences, generating a federal AMT bill of roughly $220,000 on phantom income before any liquidity.

What Documents You Need for AMT Planning

An accurate AMT projection requires:

• Form 3921 for each prior-year ISO exercise (issued by your company, shows exercise date, shares, strike price, FMV at exercise)
• Current option grant agreement showing grant date, strike price, total shares, and vesting schedule
• Most recent 409A valuation report for private company stock
• Prior-year Form 8801 showing your AMT credit carryforward if you have paid AMT in prior years
• Current-year income projection including W-2, any RSU vest schedule, bonus expectations, and any other income sources
• Section 83(b) election copies if you filed any in prior years
• California Form 3510 (prior-year credit for prior-year AMT, if applicable)

AMT and the Intersection With Other Bay Area Tax Issues

AMT does not exist in isolation. It interacts with several other planning areas that are common for Bay Area tech workers.

QSBS (Section 1202). The QSBS gain exclusion applies to federal regular tax. AMT has its own treatment: QSBS gains excluded under Section 1202 are excluded for AMT purposes as well (under the 2018 Tax Cuts and Jobs Act changes), which is a significant improvement over prior law. But the interplay between the exclusion percentage and the AMT calculation is still worth modeling.

Net investment income tax. The 3.8% net investment income tax (NIIT) under IRC Section 1411 is separate from AMT. If you sell ISO shares and recognize long-term capital gain after meeting the holding period requirements, that gain may be subject to NIIT if your modified AGI exceeds $250,000 (married filing jointly). AMT does not shield you from NIIT.

Estimated tax payments. AMT liability from ISO exercises is not typically subject to employer withholding. You are responsible for making estimated tax payments to avoid underpayment penalties. The safe harbor under IRC Section 6654 is to pay either 100% of the prior-year tax liability (110% if prior-year AGI exceeded $150,000) or 90% of the current-year liability. In a large ISO exercise year, the prior-year safe harbor is often the better choice.

State withholding on ISO exercises. California requires withholding on the ISO spread when you exercise. Your employer should report the spread as supplemental wages on your W-2. If they do not withhold correctly, you may owe California estimated taxes as well.

Service Coverage for AMT Planning Clients

Silicon Valley Tax provides the following services for clients with AMT planning needs:

• Pre-exercise AMT projection modeling comparing regular tax versus tentative minimum tax at various exercise quantities
• December-January exercise timing analysis for spreading ISO exercises across tax years
• Early exercise and Section 83(b) election filing for pre-IPO startup employees
• AMT credit carryforward (Form 8801) tracking and absorption forecasting
• California basis reconciliation for ISO shares with federal-California basis differences
• Disqualifying disposition analysis for clients who need to generate ordinary income to retire AMT credit faster
• Pre-IPO exercise strategy development coordinated with the company's equity plan administrator
• QSBS qualification analysis for ISO shares in qualifying C corporations under IRC Section 1202
• Estimated tax payment scheduling to avoid underpayment penalties in ISO exercise years
• Federal and California tax return preparation with full AMT schedule, Form 6251, and Form 8801

Our Office and How to Engage

Silicon Valley Tax is located at 2051 Junction Ave Suite 200, San Jose CA 95131. We serve clients throughout the South Bay, Peninsula, and East Bay, and we handle fully virtual engagements for clients who prefer to work remotely.

For AMT planning, we strongly recommend a planning conversation before you exercise, not after. The AMT bill is locked in when the exercise happens. Post-exercise planning is limited to managing cash flow and the carryforward. Pre-exercise planning is where the real leverage is. Call (408) 383-9870 or use the online booking form to schedule a free 30-minute consultation.

Frequently Asked Questions About AMT Tax Planning

How does exercising ISOs trigger AMT?

When you exercise incentive stock options, the spread between your strike price and the current fair market value is added to your alternative minimum taxable income (AMTI) as a preference item under IRC Section 56(b)(3). If your total AMTI exceeds the AMT exemption amount, you owe AMT at 26% or 28% on the excess. This can result in a significant tax bill on income you have not yet received as cash because you have not sold the shares. The AMT applies in the year of exercise, not the year of sale.

What is the AMT credit carryforward and how do I use it?

The AMT credit (Form 8801) is generated when you pay AMT due to timing differences like ISO exercises. In future years when your regular tax liability exceeds your tentative minimum tax, the credit offsets your regular tax liability dollar for dollar. The credit represents a prepayment of future regular tax and can be recovered over time. We model the credit absorption timeline as part of every ISO exercise analysis.

Can I do an early exercise to avoid AMT on my ISOs?

Yes. If you exercise ISOs when the 409A valuation is at or near your strike price, the AMT preference item is minimal because the spread is small. Filing a Section 83(b) election within 30 days of exercise locks in that low FMV as your tax basis. If the company grows, shares appreciate while your AMT exposure stays tied to the low FMV at exercise. We evaluate the downside risk against the AMT upside before recommending early exercise for any client.

Does California have its own AMT?

California abolished its individual AMT effective January 1, 2000. California residents do not owe state AMT. However, California does not conform to federal ISO treatment and taxes the ISO spread as ordinary income at exercise, like an NSO. This creates a California tax bill in the exercise year even though there is no California AMT. The California tax generates a compensating basis step-up used when you sell the shares.

What documents do I need for AMT tax planning around ISO exercises?

Gather: Form 3921 for each ISO exercise, your option grant agreement, the most recent 409A valuation, your prior-year tax return showing any AMT credit carryforward on Form 8801, your current-year income projections including W-2 and RSU vest schedule, and any Section 83(b) elections filed. We use all of this to build a projection of your regular tax and tentative minimum tax before any additional exercises.

Related Resources

For additional context on equity compensation tax, see our pages on equity compensation tax overview, ISO vs NSO comparison, Section 83(b) election mechanics, and post-IPO tax strategy. For Bay Area city-specific coverage, see our pages for San Jose tax accountant, Palo Alto tax accountant, and Mountain View tax accountant.