Early AI Startup ISO Exercise: The First $200k and the AMT Math

Priya is engineer #9 at Verity Labs, a pre-IPO AI company in San Francisco. She joined in mid-2022 and received an ISO grant of 95,000 shares at a $0.42 strike. The most recent 409A valuation, refreshed in January 2025, came in at $14.80. She has 76,000 ISOs vested. The spread per share is $14.38. Fully exercised today, that is $1,093,880 of AMT income. She called us asking whether to exercise any, all, or none in 2025.

Situation

Her grant and tax picture:

• 95,000 ISOs granted May 2022, $0.42 strike.
• 4-year vest, 1-year cliff, then monthly. 76,000 vested as of May 2025.
• Current 409A: $14.80. Last tender offer was at $17.60, implying the market view is slightly higher than the 409A.
• W-2 income: $245,000 base, no bonus, no RSUs (all her equity is in the ISO grant).
• Married filing jointly, spouse is an architect earning $112,000.
• Combined AGI before any exercise: $357,000.
• California residents.
• No prior AMT credit carryforward.

Under IRC §56, ISO exercise spread is a preference item for AMT. The AMT exemption for MFJ in 2025 is $137,000, phasing out at 25 cents on the dollar above $1,252,700. At her pre-exercise AGI, the AMT exemption is fully available.

Regular tax at $357k MFJ: approximately $62,800 federal plus $23,100 California. Tentative AMT without exercise: $87,200 federal. Below regular tax, no AMT owed.

The AMT crossover point, where AMT equals regular tax, is where her “first dollar of AMT pain” begins. We modeled how many shares she could exercise before crossing over.

At $0 exercise: regular tax $62,800, AMT $87,200. No AMT owed. At 10,000 shares exercise ($143,800 of AMT income): regular tax $62,800, AMT $120,000. AMT crossover reached; she owes $57,200 more.

Actually, the math was more subtle. The AMT exemption phaseout plus the AMT-income stacking meant the effective marginal AMT rate on exercised spread was 32.5% in her bracket, while her regular rate would have been 0% on the same dollars (no regular income generated by ISO exercise). So every dollar of ISO spread above the AMT-neutral threshold cost her 32.5% of cash.

What we modeled

Four exercise levels:

Shares exercised	Spread	AMT income added	Additional AMT owed	Cash cost (strike + AMT)
0	$0	$0	$0	$0
14,000 (AMT-neutral)	$201,320	$201,320	~$0	$5,880 strike
30,000	$431,400	$431,400	$108,400	$12,600 strike + $108,400 AMT = $121,000
76,000 (all vested)	$1,092,880	$1,092,880	$304,500	$31,920 strike + $304,500 AMT = $336,420

The AMT-neutral threshold was 14,000 shares, at which her tentative AMT equaled her regular tax. Below that, she pays no incremental AMT. Above, every share costs her incremental AMT at approximately 28-32.5% depending on where she lands on the phaseout curve.

The second question was the §1202 angle. Verity Labs is a C-corp and likely QSBS-eligible. ISO exercise starts her §1202 5-year clock on the exercised shares. If Verity exits at year 5 or later, the gain on the exercised shares qualifies for §1202 exclusion up to the $10M cap (or $15M for shares exercised after July 4, 2025 under OBBBA). The earlier she exercises, the earlier the clock starts.

Third question: if she holds post-exercise for 1 year after exercise plus 2 years after grant (meeting the §422 holding requirements), the eventual sale qualifies as an ISO qualifying disposition, taxed at long-term capital gains rates on the full sale-minus-strike spread. If Verity is sold before she hits the §422 holding requirement, the exercise becomes a disqualifying disposition, treated as ordinary W-2 income on the bargain element.

What she did

She exercised 14,000 shares at the AMT-neutral threshold in March 2025. Strike cost: $5,880. AMT cost: ~$0. This started her QSBS clock and her ISO §422 holding clocks on those 14,000 shares.

She also exercised an additional 6,000 shares in December 2025 as a deliberate AMT-generating exercise, accepting about $22,000 of additional AMT. Her reasoning: Verity’s 409A might reset higher in 2026, which would make future exercises more expensive, and the 6,000 shares positioned her for a partial QSBS benefit even if the first-12,000 position grew large enough to cap out.

Total cash out of pocket in 2025: $14,280 of strike payments plus $22,000 of AMT = $36,280. Total ISOs held: 20,000 with the clock started.

She left 56,000 vested ISOs unexercised. Her plan: re-evaluate each year based on 409A movement and Verity’s progress toward a liquidity event.

What she wishes she had done differently

The biggest regret: she did not early-exercise at the cliff in May 2023, when the 409A was $2.10 and the spread was $1.68. At that time she had 23,750 vested ISOs. Exercising all 23,750 at $2.10 would have cost $49,875 in strike plus approximately $0 of AMT (the spread at $1.68/share on 23,750 shares was $39,900 of AMT income, well within the exemption). She would have locked in a 2-year §422 clock from that date and a 5-year §1202 clock, and her entire vested position would have been QSBS-eligible well before any 2025 exit. Instead, by waiting until 2025, her 14,000 shares will not be §1202 eligible until March 2030. If Verity is acquired in 2028, she pays ordinary rates on $14,380 × 14,000 = $201k of disqualifying-disposition income, plus capital gains at short-term rates on the post-exercise appreciation.

Second regret: she did not file a §83(b) election when she had the opportunity through Verity’s early-exercise provision. Her grant allowed early exercise of unvested ISOs, which would have let her buy all 95,000 shares at the $0.42 strike in June 2022 when she joined. The spread at that time was essentially zero (the 409A was $0.42 at issuance). A §83(b) election would have locked in the full 95,000 shares at near-zero cost, started the §422 and §1202 clocks immediately, and eliminated all future AMT. The cost: $39,900 out of pocket in 2022.

The reason she did not: no one told her about the option, and her offer packet did not emphasize early exercise. She found out about it from a colleague 18 months later.

Third regret: she held off on exercising because she was nervous about spending cash on shares that might be worthless. This is a real concern for early-stage companies. But at 14,000 shares with $0 of AMT, her risk was $5,880, not $300k. The risk-reward was favorable even in the downside case where Verity shut down.

Frequently asked

What is AMT and how does it apply to ISOs?

The Alternative Minimum Tax is a parallel tax system with its own deductions and rates. Under IRC §56, the bargain element on ISO exercise (FMV minus strike on exercise date) is added to AMT income, even though it is not regular taxable income. If AMT exceeds regular tax, you pay AMT. The 2025 AMT exemption is $137,000 MFJ, phasing out above $1,252,700.

What is an AMT-neutral exercise?

An exercise size where the resulting AMT equals your regular tax, so no incremental AMT is owed. This is the “free” portion of ISO exercise, typically 5,000 to 15,000 shares depending on income and spread per share.

How do I recover AMT paid on ISO exercise?

AMT paid creates an AMT credit under IRC §53, carryforward indefinitely. In years when regular tax exceeds AMT, the credit offsets regular tax. For ISO holders, the credit is often recovered over 5-15 years depending on income patterns.

Does ISO exercise count for QSBS?

Yes. §1202 applies to stock acquired by exercise of ISOs, assuming all other §1202 requirements are met. The 5-year holding period runs from exercise.

What happens if my company is acquired before I meet the §422 ISO holding period?

If you sell exercised shares within 2 years of grant or 1 year of exercise, the exercise becomes a disqualifying disposition. The bargain element at exercise is treated as ordinary compensation (W-2 income), and the post-exercise gain is short-term or long-term capital gain depending on holding period.

Composite scenario drawn from common patterns in our advisor network's casework. Names, companies, and exact numbers are illustrative. Not tax, legal, or investment advice.