Two ways to create an invoice
Create an invoice from scratch with line items, quantities, rates, discounts and notes, or use Invoice from time to draft one from a project’s approved billable time for a billing period. The time preview shows what will be billed and what was left out of the draft (for example, time that isn’t approved yet or has no rate), and you can add fixed fees such as a monthly retainer.
Time that’s already on an invoice can’t be billed twice. If you remove a line from a draft, its time goes back to unbilled.