In the event you have a zero priced item (intentionally or unintentionally), you may want the user to key in the price if its zero. This can be setup store by store and is located in the POS Functionality Profiles record.
Requiring the zero priced item to have a new price can be helpful at the beginning of a project, but can also create a lot of headaches so make sure you have a process in place to identify zero priced items rather than rely on this setting. It shouldn't be used as a catch all magic button for those issues.
I always struggle to remember where the setting is so I'm posting about it for next time I put it in the search engine.