What permissions do you need to see the P&L tab?

Accounts permission I believe. Just keep in mind that if you turn that permission on just so they can see the P&L on projects, they also will have the ability to see the chart of accounts and whatnot. We recently had this turned on in error for a role (for the same purpose), and later realized they were able to see our chart of accounts when we didn't want them to O_O