Equity Timing Lab

Personal finance · Equity decisions

Know when the tax benefit is worth the price risk.

Compare a proposed sale with the next ESPP or vested-RSU holding milestone, then translate the modeled tax difference into a break-even future stock price.

Deterministic computation decides; probabilistic intelligence explains.

DeterministicCalculation engine

Versioned2025 federal + California profile

ExactFull-precision arithmetic · two-decimal display

Private by designFinancial data is not stored

01 · Model inputs

Build the comparison

2025 profileCalifornia residentConstant-law comparison

ESPPQualified Section 423 sharesVested RSUAlready vested and stock settled

Enter acquisition facts from your plan records. Values accept up to eight decimal places.

Qualified Section 423 assertionI confirm these shares were acquired under a qualified Section 423 employee stock purchase plan.

Offering/grant date

Form 3922 Box 1.

Grant-date FMV per share

Form 3922 Box 3.

Grant-date as-if exercise price

Use Form 3922 Box 8 when provided: the exercise price determined as if the option were exercised on the grant date.

Purchase/exercise date

Form 3922 Box 2.

Purchase-date FMV per share

Form 3922 Box 4.

Actual purchase price per share

Form 3922 Box 5.

V0 uses the Form 3922 Box 2 purchase/exercise date as the transfer and acquisition date; it does not separately model the Box 7 transfer date.

Number of shares

Form 3922 Box 6.

Proposed sale date

Calendar date only; timestamps are rejected.

Proposed price per share

Fixed total selling fee

One fixed total amount for the entire sale.

These values model incremental tax. They do not prepare a complete return.

Filing status

Federal ordinary taxable income

After deductions, but before the capital items below and this transaction.

California ordinary taxable income

After deductions, but before the capital items below and this transaction.

Estimated baseline MAGI

Excludes this equity transaction but includes other income and the existing capital context.

Existing net short-term capital gain / loss

Include available carryovers. Enter a negative amount for a loss.

Existing net long-term capital gain / loss

Include available carryovers. Enter a negative amount for a loss.

Estimated baseline net investment incomeOptional — required to include NIIT

Required for NIIT. If omitted, totals and break-even are explicitly shown excluding NIIT.

Advanced assumptionsOptional jurisdiction-specific rate overrides

Apply advanced marginal-rate overrides

Fixed V0 context

Tax year 2025 · Full-year California resident · 2025 rules held constant for wait comparisons · No federal/California RDP-status differences.

Educational estimate only—not tax, legal, or investment advice. Results use simplified assumptions and may not reflect your complete tax return or future law. Consult a qualified tax professional before making financial decisions.

How the lab works

The calculation stays separate from the interface.

1Validate

Date-only and decimal-string inputs are checked against shared contracts.

2Recalculate

The server computes baseline, proposed, and milestone outcomes from the deterministic engine.

3Compare

The complete tax function searches for the lowest cent-denominated wait threshold.

Know when the tax benefit is worth the price risk.

Build the comparison

Instrument

Equity details

Tax context

The calculation stays separate from the interface.