Why a multi-year optimizer, not a chatbot, for equity-comp math

Five frontier large language models were asked the same Incentive Stock Option (ISO) exercise problem: 50,000 vested shares, $4 strike, $90 fair market value, four-year horizon, California resident, single filer, 5% cash return. Each model got three independent runs. Fifteen trials in total.

Every one of the 15 trials overshot reality by 2x to 20x on the after-tax outcome it claimed for its proposed schedule. None recovered the globally-optimal plan that the optimizer returns in under a second.

Full benchmark write-up: HackerNoon: But can it do taxes though?

Three properties, all simultaneously:

1. Globally optimal. The returned schedule is the best across the full candidate space the engine searches: every feasible share-per-year combination, scored against the full tax cost function across your horizon.
2. Full tax-code coverage. Federal (ordinary brackets, long-term capital gains, AMT with credit recovery, FICA, Net Investment Income Tax) plus all 50 states and DC (state ordinary brackets and LTCG treatment; state AMT modeled for CA, NY, MN). No state-skipping, no bracket approximation.
3. Verifiable. Same inputs always return the same schedule, so the recommendation is reproducible. Re-running the tax math end-to-end on the chosen plan reproduces the headline outcome to the cent.

The free calculators on this site compute against current-year tax authorities, not learned approximations:

• Tax brackets sourced from IRS Rev. Proc. 2025-32 and the One Big Beautiful Bill Act (OBBBA) for tax year 2026.
• Per-state ordinary brackets and long-term capital gains (LTCG) treatment for all 50 states plus DC, with explicit AMT modeling for CA, NY, and MN.
• Validated against 870+ unit tests covering bracket walks, AMT credit recovery across years, state conformity, and the optimizer's search path.
• Multi-year ISO schedule optimization returns the globally-optimal exercise plan across the search space, not a sampled candidate.

Full math sourcing and known scope gaps: /methodology.

• AMT + ISO Exercise Calculator
  Plan a multi-year ISO exercise schedule that minimizes AMT — federal and state, with credit recovery and grant-expiration timing.
• NSO Exercise Calculator
  Calculate the after-tax payout on a non-qualified stock option exercise (federal, state, FICA), then compare selling now vs. holding for long-term capital gains across your chosen horizon.
• RSU Sell-vs-Hold Calculator
  After your RSUs vest, should you sell at vest or hold? Compare after-tax payout — federal, state, FICA, plus the short-term-vs-LTCG cliff at 12 months — and see exactly what holding actually costs.
• Stock Concentration Calculator
  See how concentrated your single-stock position is, what a 30/50/70% drawdown costs, and the trade-off between selling down and hedging — with multi-year tax math.
• Protect Your Stock Calculator
  Price a zero-cost collar or protective put on a single-stock position. See annual cost, max loss, upside cap, bad-year coverage, and which structure suits your floor.
• QSBS Qualification Checker
  Does your founder or employee stock qualify for the Section 1202 QSBS exclusion? Check eight tests, see your exclusion percentage, federal tax saved, and state conformity — all instant.

If you build agents that help users with equity compensation, /for-agents has the integration surface: REST API at /api/v1, Model Context Protocol (MCP) server at /mcp, OpenAPI 3.1 spec, schema.org JSON-LD on every tool page, and a public /llms.txt capability index.