Deposits and credit that always add up

Customer deposits and credit sound simple until real life happens: a deposit partly used, then the rest refunded; an invoice settled by credit, then voided. Papertools now keeps the whole story straight, in every direction.

• A deposit has three exits: apply it to an invoice, refund it home, or both — and every ceiling does the subtraction, so credit can never be spent twice.
• Void an invoice that credit settled, and the credit walks back to the customer on its own. Same courtesy on the other side of the counter: void a bill and your supplier credit returns.
• Every document tells one story — the invoice PDF explains the credit that settled it, statuses say used, given back, or both, and "settled" means settled no matter who paid it.

The kind of correctness you only notice when it's missing — so now you won't.