Lock-Up Period vs Vesting: Key Differences Explained

A lock-up period is a contractual restriction that prevents insiders (founders, employees, early investors) from selling their shares for a defined period after an IPO, typically 90–180 days. Lock-ups are required by underwriters and the SEC to prevent the immediate insider selling that would signal a lack of confidence in the public company and potentially crash the stock price. After lock-up expiration, insiders can sell shares freely (subject to trading windows and Rule 144 restrictions). Lock-up expirations are closely watched by public market investors because large insider selling can depress share prices. Some companies voluntarily extend lock-ups or impose trading blackouts around earnings to signal confidence. The lock-up is a contract with the underwriters, not a statute — its exact scope lives in the underwriting agreement and in the insider lock-up agreements signed before the IPO. Modern lock-ups are increasingly structured: some companies negotiate staggered releases, for example a portion of shares released early if the stock trades a set percentage above the IPO price for a sustained period, and direct listings frequently dispense with a traditional lock-up entirely. Acquisitions create lock-up-like restrictions too: in a stock-for-stock deal, sellers commonly receive acquirer shares subject to contractual resale restrictions or escrow holdbacks, so "we got acquired" rarely means "we got liquid on day one." Affiliates also remain subject to Rule 144 volume limits even after the lock-up ends.

Vesting is the process by which equity ownership is earned over time according to a schedule. The standard startup vesting schedule is 4 years with a 1-year cliff: nothing vests in the first 12 months, 25% vests at the 1-year anniversary, then monthly vesting for the remaining 3 years. Vesting applies to both founder equity (to protect investors and co-founders if someone leaves early) and employee stock options (to incentivize employees to stay). Vesting exists to align equity with contribution: someone who stays 4 years earns all their equity; someone who leaves after 1 year forfeits most of it. Double-trigger acceleration is a common vesting protection: if the company is acquired AND the employee is terminated, unvested equity accelerates. Vesting also governs what happens on departure and at exit. Options typically carry a post-termination exercise window — commonly 90 days — so leaving means either paying to exercise vested options or losing them. RSUs at private companies are frequently double-trigger for tax reasons: they require both service-based vesting and a liquidity event before they settle, which is why a long-tenured employee can hold fully service-vested RSUs that still deliver nothing until an IPO or acquisition. Founders should also expect re-vesting conversations: it is common for a new lead investor to ask founders to put a portion of already-vested shares back on a vesting schedule as a condition of the round.

Both matter at different stages. Vesting drives pre-IPO behavior and equity alignment across the entire company journey. Lock-up periods are a crucial IPO-stage concern for financial planning. Every equity holder should understand both mechanisms, because the combination — vesting schedule + lock-up period — determines when they can actually convert equity to cash. Secondary sales are where the two regimes visibly interact before an IPO. Company-run tender offers almost always limit participation to vested shares — often with a percentage cap on each holder's vested position — and private-company transfer restrictions (rights of first refusal, board consent requirements) function as a de facto lock-up throughout the private years. So the practical sequence for any equity holder is: vest it, clear the private transfer restrictions or wait for a tender window, then clear the public lock-up.

A founder has 2 million shares, fully vested after 4 years at the company. The company goes public. The lock-up period prevents her from selling any shares for 180 days post-IPO. On Day 181, she can sell up to a certain amount (subject to trading windows, 10b5-1 plan rules, and company blackout periods). Meanwhile, a new engineer who joins the company 6 months before IPO has a 4-year vesting schedule: they've vested 12.5% of their options by IPO day, but can't sell the underlying shares until after the lock-up AND after their options are exercised. A fuller timeline makes the interaction concrete. A founder starts in January 2020 with 4,800,000 shares on a standard 4-year schedule with a 1-year cliff. January 2021: the cliff vests 25%, or 1,200,000 shares. Thereafter 100,000 shares vest monthly (3,600,000 remaining over 36 months). In June 2023 — month 42 — she has vested 1,200,000 + 30 × 100,000 = 4,200,000 shares, and the company runs a tender offer letting holders sell up to 10% of vested shares at $12.00 per share: she sells 420,000 shares for $5,040,000 while the company is still private. January 2024: fully vested at 4,800,000 shares (4,380,000 still held after the tender sale). June 2025: the company IPOs at $20.00, and her shares are locked for 180 days. Around December 2025 the lock-up expires and she can begin selling — subject to open trading windows and, as a likely affiliate, Rule 144 volume limits. Note that the two mechanisms never overlapped in function: vesting determined how much equity she owned; the lock-up determined when she could convert it to cash.