Financial Glossary
Lock-Up Period
A lock-up period is a contractually specified window following an IPO or other liquidity event during which company insiders -- founders, executives, employees with vested options, and pre-IPO investors -- are prohibited from selling their shares on the open market. Lock-ups are typically negotiated with the underwriters and run for a defined period after the IPO date. Their purpose is to prevent a flood of insider selling from driving down share price immediately after listing, preserving market stability during the critical early trading period. Lock-up expirations often trigger elevated trading volume and share price volatility.
Problem & Application
A founder holds 4 million shares after an IPO priced at $12 per share. A standard lock-up restricts sales for a defined period post-listing. If the stock rises to $18 during that window, the founder has unrealized gain but cannot liquidate. Tax planning ahead of the lock-up expiration becomes critical: if the founder sells all shares on the first day eligible, the concentrated income may push them into the highest federal bracket for that year. A CFO or tax advisor working with the founder before the lock-up expires develops a staged selling plan -- often using a pre-planned trading arrangement to spread sales across multiple quarters -- reducing average tax rate and avoiding the appearance of an insider dumping shares, which can spook other investors even when perfectly legal.
In Short
Lock-up periods help stabilize stock prices after an IPO and prevent a flood of shares entering the market too soon.