Team admins choose the team's currency on the team page, and Personal currency is under Account details in Account settings. New invoices, expenses, asset prices, time rates and appointment prices start in it, and a new team starts with the creator's Personal currency. Records already made keep their own currency.
Existing teams were given the currency they already used for Invoicing, Payments or Store. A team that used none of these shows its currency as not chosen and uses USD until one is chosen.