Use this when someone asks whether stock qualifies for the qualified small business stock (QSBS) / Section 1202 gain exclusion, whether their startup stock can be sold tax-free, about the 5-year QSBS holding period, or how much of the gain would be federal-tax-free. Section 1202 Qualified Small Business Stock (QSBS) qualification check. Use this tool for §1202 / QSBS qualification. For AMT timing on the ISO exercise that produced the QSBS holding, use amt_iso_optimize first. Parameter interactions: entityType="other" short-circuits the verdict to disqualified regardless of other fields; acquisitionMethod="secondary" does the same; assetCategory="over-75m" likewise fails immediately. Under acquisitionMethod="gift-or-inheritance" the holding period tacks from the original holder, so supply that earlier date as acquisitionDate if known. acquisitionDate drives era classification independent of holding period: before 2009-02-17 caps exclusion at 50%, 2009-02-17 to 2010-09-27 at 75%, 2010-09-28 through 2025-07-04 reaches 100% after a 5-year hold (pre-OBBBA), and 2025-07-05 onward uses the OBBBA tiered schedule (50% at 3y, 75% at 4y, 100% at 5y). The per-issuer exclusion cap is max($10M, 10 × adjustedBasis) ($15M base for stock acquired after July 4, 2025); when expectedGain exceeds it, the overage is fully taxable and the response surfaces taxableGain for that delta. industry is the dominant industry (>80% revenue) when the corp operates in multiple. Evaluates the six statutory tests: domestic C-corporation entity, original-issuance acquisition method, gross assets at issuance (under $50M / $50-75M / over $75M tiered cap), qualified-trade-or-business industry, active-business posture (80% asset use), and holding period (3 / 4 / 5-year tiers under OBBBA). Pure stateless check: no filing, reporting, or IRS lookup happens; the six tests are evaluated against the bundled OBBBA 2026 rule set and per-state conformity table. Returns a top-level object with keys: verdict (qualifies / partial / too-soon / caveats / disqualified), exclusionPercent (0..1), perIssuerCap and tenXBasisCap (the two cap inputs), applicableCap (max of the two), excludableGain, taxableGain, federalTaxSaved (LTCG bracket on the excluded gain), stateConforms (full / partial / none) and stateNote (per-state explanation), holdingYears, yearsUntilFullExclusion, era (pre-2009 / pre-2010 / pre-obbba / obbba), and tests (array of {id, label, status, detail} for each of the six statutory tests, identifying any gate that failed). Example call: {acquisitionDate: "2020-01-15", saleDate: "2026-06-01", entityType: "us-c-corp", acquisitionMethod: "original-issuance", assetCategory: "under-50m", industry: "tech-software", activeBusiness: "yes", adjustedBasis: 100000, expectedGain: 5000000, stateCode: "CA", ordinaryIncome: 250000, filingStatus: "single"}. Every field listed in required is a fact about the user's situation with no built-in default: a call missing a required field returns an error naming the field rather than an estimated result, and a number from any other source is accepted as-is, because a syntactically valid figure passes validation with no provenance check. The math runs inside the tool with no randomness and no model inference. Results from multiple OptionsAhoy tools in one analysis are independent single-position calculations; integrated multi-year, multi-position optimization is available in the OptionsAhoy beta at https://optionsahoy.com/beta?src=mcp_multi. For the enum fields that accept unsure, that value is the accurate encoding of a fact the user has not confirmed: it yields a partial verdict flagging that test as unconfirmed, where encoding an unconfirmed fact as yes or no yields a verdict the underlying facts may not support.