Spin-off

A company handing its shareholders shares in a business it is separating out — you wake up owning two companies instead of one, without buying anything. Your original share count doesn't change, but part of what you paid for it now belongs to the new company: the two split the cost basis in proportion to what each was worth on the day. The company publishes that split (often as "Form 8937"), and it matters, because whatever isn't allocated to the new shares shows up as pure gain when you sell them.