Buy-Sell Agreement: The Contract That Governs What Happens When a Co-Owner Leaves

A contract between co-owners of a business that governs what happens to an owner's stake if they leave — who can buy it, and at what price. Despite the name, it has little to do with selling the company to an outside buyer; it's really a buyout agreement between the existing owners.

Why it matters: Without one, a departing owner (due to retirement, disability, divorce, or death) could transfer their share to anyone, disrupting the remaining owners. This matters most acutely for owners running multi-partner businesses — restaurants, medical and professional practices, contracting firms — where a surprise new "partner" (an ex-spouse, an estranged heir, an outside buyer of a departed partner's stake) can derail day-to-day operations and tank the value of the whole business right when you're trying to build toward your own exit. A well-drafted agreement also protects the business in a divorce: it can require a former spouse who receives an ownership interest in the settlement to sell it back to the company or co-owners at a price set by a valuation method spelled out in the agreement.

Buyers evaluating a multi-owner business during due diligence will often ask to see this document early — its absence, or a poorly drafted one, is a red flag about how cleanly ownership can actually transfer.

Example (illustrative only): Two partners co-own an HVAC company. One partner is diagnosed with a long-term disability and can no longer work. Without a buy-sell agreement, the disabled partner (or their family, if it worsens) retains full ownership rights indefinitely, with no mechanism forcing a buyout — leaving the working partner stuck co-managing the business with someone who can't contribute. A buy-sell agreement with a disability trigger and a pre-agreed valuation formula avoids that standoff.

Related terms: Employee Stock Ownership Plan (ESOP), Co-op, Purchase Agreement