A written agreement that transfers ownership of intellectual property from the creator to the company.
An IP assignment is a formal written agreement under which the person who created something — code, designs, processes, written content — transfers ownership of that intellectual property to another party, typically the company. Under copyright law, the creator automatically owns what they create unless there's either a work-for-hire relationship (for employees) or a signed assignment agreement (for anyone else).
IP assignments are important in several situations: founders assigning pre-existing IP they built before incorporating, contractors assigning work they created, and advisors or consultants assigning any materials they develop. The assignment should be broad enough to cover all related IP (including continuations and improvements), should include consideration (something of value in exchange), and should include a provision for the person to assist with any future registration or documentation of the IP.
For funded startups, clean IP ownership is non-negotiable. If your company's product or technology was created by people who haven't signed assignments, the company may not actually own its own IP — a fact that will surface in due diligence and can be very expensive or impossible to fix retroactively.