Biogen Employee Stock Purchase Plan

How enrollment works

Most ESPPs are funded through after-tax payroll deductions during an enrollment window. You choose a percentage of pay to set aside, and on the purchase date the plan buys shares on your behalf -- at a discount, and with a lookback if the plan offers one. The discount and lookback are what make an ESPP different from simply buying shares on the open market.

Hold versus sell

After shares are purchased, participants generally face a choice between selling soon after purchase or holding for a longer period. Selling quickly locks in the built-in discount but concentrates the proceeds in a single stock for less time; holding longer can change the tax treatment but adds exposure to that one company's share price. Which path makes sense depends on your overall financial picture, not on the plan terms alone.

Tax treatment, in general

For Section 423-qualified plans, the discount and any gain are taxed differently depending on how long you hold the shares -- a "qualifying disposition" (holding past statutory periods) versus a "disqualifying disposition" (selling sooner) are taxed in different ways. Non-qualified plans follow different rules. This is general educational information, not tax advice; the IRS rules are specific and your own situation determines the outcome.