What is an ESPP?
An Employee Stock Purchase Plan lets you buy your employer’s shares through after-tax payroll deductions, usually at a discount of up to 15%. Money builds up during an offering period (commonly six months), and shares are bought on the purchase date.
The lookback feature
Many plans compare the share price at the start of the offering period with the price on the purchase date and apply the discount to whichever is lower. If the stock rises from $40 to $50 and the discount is 15%, your price is $40 × 0.85 = $34, and the shares are worth $50 on the day you buy them. That is an instant 47% return on the money you contributed.
Qualifying vs disqualifying dispositions (US)
| Qualifying disposition | Disqualifying disposition | |
|---|---|---|
| Holding test | Sold 2+ years after the offering date and 1+ year after purchase | Sold earlier |
| Ordinary income | Lesser of actual gain or the discount measured on the offering-date price | Market value at purchase minus purchase price |
| Rest of the gain | Long-term capital gain | Capital gain or loss (short- or long-term) |
How this ESPP calculator works
The calculator sets your purchase price from the lookback and discount, divides your contributions by that price to get your shares, then splits your gain into ordinary income and capital gain according to the disposition you choose. Taxes are estimated using the two rates you enter; it does not model state taxes, the 3.8% net investment income tax, or alternative minimum tax.
Is it worth selling immediately?
Many employees sell on the purchase date to lock in the discount, which turns the ESPP into a guaranteed bonus. Holding for the qualifying period can reduce tax but exposes you to share price risk, often in the same company that pays your salary. Check how much of your wealth is already tied to your employer.
UK employees
UK companies do not typically offer ESPPs in this form. The nearest UK equivalents are Share Incentive Plans and SAYE (Save As You Earn) schemes, which are tax-advantaged. UK employees of US companies may be offered an ESPP and should seek advice on UK income tax and National Insurance on the discount.
Frequently asked questions
What is an ESPP lookback?
A feature that applies the plan discount to the lower of the share price at the start of the offering period and the price on the purchase date. It can raise the effective discount well above the headline percentage when the stock is rising.
What is the maximum ESPP discount?
Under US Section 423 plans the maximum discount is 15% of fair market value. You can also buy no more than $25,000 of stock (valued at the offering date) in any calendar year.
When is ESPP taxed?
Not at purchase. Tax arises when you sell the shares. How it is split between ordinary income and capital gains depends on whether the sale is a qualifying or disqualifying disposition.
Should I sell ESPP shares immediately?
It depends on your risk tolerance and tax position. Selling at once locks in the discount; holding for the qualifying period may reduce tax but leaves you exposed to price falls.
Is an ESPP the same as a Share Incentive Plan?
No. An ESPP is a US plan using after-tax contributions. A UK SIP is an HMRC-approved scheme where partnership shares are bought from pre-tax salary and held in trust.