10b5-1 Sell-Down Calculator

Enter your current position, total portfolio value, and diversification target. The calculator builds a full sell schedule — shares per window, after-tax proceeds, and employer-stock concentration at each stage.

What the schedule assumes

• Even distribution. Shares are divided equally across all windows. Your actual plan can use fixed share amounts, fixed dollar amounts, or price-conditional triggers — even distribution is the simplest baseline.
• Static stock price. The calculator holds price constant for projection purposes. If the stock appreciates, your concentration stays higher than projected; if it falls, you'll get less proceeds.
• All gains are long-term. Assumes your full cost basis was established more than 12 months ago. Short-term gains (held ≤12 months) are taxed at ordinary income rates — much higher for executives.
• No volume limit. The SEC doesn't specify a hard maximum shares-per-window, but most plans cap sales at 10–25% of average daily trading volume (ADV) to avoid market impact. The model ignores ADV — your compliance team should confirm volume feasibility.
• Portfolio value held constant. Assumes proceeds are reinvested at comparable return to overall portfolio. This keeps concentration math consistent across windows.

Tax considerations for 10b5-1 sell-downs

2026 federal LTCG rates: 0% (taxable income ≤ $49,450 single / $98,900 MFJ), 15% (up to $533,400 single / $613,700 MFJ), 20% above those thresholds.¹ Most executives selling concentrated positions will be in the 20% bracket.

Net Investment Income Tax (NIIT): An additional 3.8% on capital gains applies once modified AGI exceeds $200,000 (single) or $250,000 (MFJ).² This threshold is set by statute and is not inflation-indexed. Combined federal LTCG rate for high-income filers: 23.8%.

State tax stacking: California taxes capital gains as ordinary income (up to 13.3%). New York is ~10.9%. Texas, Florida, and Washington have no income tax. If you're considering a state move before executing your plan, the timing matters enormously — a $5M sell-down at 13.3% CA vs. 0% WA is a $665,000 difference.

NQDC coordination: If you also have NQDC distributions scheduled, stacking sell-down proceeds and NQDC in the same year compounds the bracket effect. Map both income streams before filing the plan.³

Charitable giving: Donating appreciated shares directly to a DAF (donor-advised fund) eliminates the capital gain entirely and generates a full fair-market-value deduction. Consider allocating a portion of concentrated stock to charity before the 10b5-1 sells it.

The 2023 SEC amendments — what they changed

Rule 10b5-1 was significantly tightened effective February 27, 2023. These changes are now standard; any plan adopted or modified after that date must comply:

• Cooling-off period for officers/directors: the later of (a) 90 days after plan adoption, or (b) two business days after the company files the quarterly report for the quarter of adoption — capped at 120 days.⁴
• Cooling-off for others: 30 days.
• Single-plan rule: generally one active plan at a time.
• Certification requirement: officers/directors must certify in writing at adoption that they are not aware of material non-public information.
• Modification = new plan: any modification triggers a new cooling-off period. Design your plan with foresight — you cannot adjust for market conditions.