QSBS Calculator
The QSBS calculator estimates how much of your startup stock sale is federally tax-free under IRC §1202. It auto-selects the legacy or OBBBA rule set from your acquisition date, applies the per-taxpayer cap, checks state conformity, and models trust stacking.
How to use this calculator
- Enter your grant: Add acquisition date, share count, cost basis, expected sale price, and expected sale date.
- Confirm eligibility: Select the issuing entity type, your state of residence, and whether the company met the gross-asset test at issuance.
- Add stacking: Optionally toggle stacking to model gifting shares to non-grantor trusts or family members.
- Review the result: See the excluded gain, taxable gain, federal and state tax, net proceeds, and days until the next exclusion tier.
Assumptions
| Assumption | Value |
|---|---|
| Rule set | Legacy (≤ 2025-07-04) or OBBBA (> 2025-07-04) auto-selected |
| Cap (legacy / OBBBA) | max($10M, 10× basis) / max($15M, 10× basis) |
| Gross-asset test | $50M legacy / $75M OBBBA at issuance |
| State conformity | CA, NJ, PA, MS, AL don't conform to §1202 |
| NIIT | 3.8% on non-excluded investment income above MAGI floor |
Frequently asked questions
What is QSBS?
Qualified Small Business Stock under IRC §1202 lets shareholders exclude a large portion of federal capital gain when they sell C-corp stock, provided a set of issuance, holding-period, and active-business tests are met.
How long do I have to hold the stock?
Legacy rules require 5 years for any exclusion. OBBBA rules (stock acquired after 2025-07-04) unlock 50% at 3 years, 75% at 4 years, and 100% at 5 years.
What's the cap on excluded gain?
Legacy: the greater of $10M or 10× adjusted basis per taxpayer. OBBBA: the greater of $15M or 10× adjusted basis per taxpayer.
Does my state honor §1202?
Most do, but California, New Jersey, Pennsylvania, Mississippi, and Alabama don't conform — they tax the full gain at the state level even when it's federally excluded.
What is QSBS stacking?
Gifting shares to non-grantor trusts or family members creates additional §1202 taxpayers, each with their own per-issuer cap. This multiplies the total excluded gain, but requires advance planning and proper trust drafting.
What is the 10× basis rule?
Even above $10M / $15M, gain up to 10× your adjusted basis in the stock is excludable. Founders with very low basis usually hit the dollar cap first; buyers of secondary shares may benefit more from the 10× branch.
Does exercising ISOs start the QSBS clock?
Yes — the holding period begins when you acquire the stock, which for ISOs is the exercise date, not the grant date.
What if the company grew past $50M or $75M in assets after issuance?
The gross-asset test only applies at the time of issuance. Later growth doesn't disqualify already-issued QSBS shares.
Can converting from LLC to C-corp reset the clock?
Yes. Stock issued at conversion is treated as newly issued for §1202. The holding period starts at conversion, and the gross-asset test is measured at that point.
Is this tax advice?
No. This calculator is an illustrative planning estimate and is not tax, legal, or investment advice.