Does buying out my business partner need the same paperwork as buying a whole company?

Largely yes, though the paperwork can often be scaled to the situation. A partner buyout is still a share, or sometimes asset, purchase, so it typically involves a purchase agreement with representations and warranties, a disclosure schedule, closing conditions, and provisions dealing with price and payment — the same core building blocks as buying an entire company from a stranger.

What's often different in practice is the depth of due diligence, since a partner already knows the business intimately and may not need the same investigation a true outsider would conduct. That familiarity doesn't eliminate the value of clear representations about things like undisclosed liabilities, related-party dealings, or ongoing disputes the departing partner may know about, though. Corporate approvals, updates to the minute book, and any changes needed to banking, licences, or registrations still need to happen just as they would in a full company sale, even though only one owner is actually leaving.