Work made for hire
Definition
The narrow rule that decides whether you own what somebody built.
Why It Matters
The default runs the other way from what most owners assume. Copyright in something an EMPLOYEE makes inside their job belongs to the business; copyright in something a CONTRACTOR makes belongs to the contractor, and calling it a work made for hire in an email does not move it. The freelancer who drew the logo, built the site or wrote the software owns it unless a signed assignment says otherwise, and what the business has instead is an implied permission to keep using it. For a buyer that is a diligence line with a cheap fix and an expensive absence: ask for the assignment on every mark, site and codebase the price depends on, and where none exists the seller can usually still get one before closing. Afterwards the leverage is gone.
In numbers: A logo a freelancer drew for $800 and never assigned is the asset a $4M purchase agreement cannot transfer.