Founders Stock Vesting Tax Acceleration Calculator
Founders stock vesting can accelerate on an acquisition event. Calculate the tax impact of single-trigger (acceleration on change-of-control) vs double-trigger (acceleration on change-of-control + termination) acceleration on a typical founder grant.
| Total Founder Shares | — |
| Vested at Acquisition | — |
| Unvested at Acquisition | — |
| Shares Accelerated | — |
| Total Shares Sold | — |
| Acquisition Price/Share | — |
| Gross Proceeds | — |
| Gross Capital Gain | — |
| 83(b) Filed? | — |
| QSBS Qualified? | — |
| Total Tax | — |
| Net After-Tax | — |
Single vs Double Trigger Acceleration
Single-trigger acceleration: all unvested shares vest immediately on change-of-control (acquisition, IPO). Founder-friendly but reduces acquirer's key-talent retention leverage. Rarely used in modern term sheets.
Double-trigger acceleration (more common): unvested shares only accelerate if (a) the company is acquired AND (b) the founder/employee is terminated without cause (or resigns for good reason). Aligns founder with acquirer's post-close transition plan. Standard in most VC term sheets.
Tax Treatment of Accelerated Shares
Accelerated shares are taxable as if they vested on the acceleration date. With 83(b) filed: all gain is capital gain (LTCG if held 1+ years from purchase). Without 83(b): the bargain element at vest is ordinary income (W-2), subsequent appreciation is capital gain.
Founder shares typically: low FMV at grant + 83(b) filed = nearly all gain is LTCG. Acquisition triggers liquidity event, taxable at LTCG rates (20% + 3.8% NIIT).
QSBS Compatibility
If founder shares qualify for §1202 QSBS (C-corp, gross assets ≤$50M at issuance, held 5+ years from acquisition date), up to $10M (or 10x basis) of gain can be excluded from federal tax entirely.
Acceleration on acquisition can break the 5-year QSBS hold requirement if you've held less than 5 years. Some founders structure to extend the wait or use §1045 rollover to defer. See our QSBS calculator.
Source: irs.gov IRC §1202 + Section 1045
Negotiating the Trigger
Single-trigger acceleration: rare in seed/Series A, more common in later-stage hires brought in for a planned exit. Founders typically don't get single-trigger on the initial founder grant.
Double-trigger acceleration: standard for senior hires (VP+). Often includes 12-24 months of acceleration on termination without cause within 12-24 months of acquisition. Negotiate this at hiring — much harder to get post-hire.