Every proposal payment is a regular Sprwt checkout, so it appears under Checkouts in the admin (click the ID on the Payments tab) and in the customer's order history with the usual receipt/confirmation page and emails. On the proposal itself the customer-facing page and the printed PDF include a Payments History block (payment, paid on, method, amount) and the totals show Paid and Balance Owed. For an invoice-style document set the proposal's Type field to Invoicing (Proposal Details section) and use Print to produce the PDF; the Account Receivable Report (/admin/events/accountsreceivable, permission Proposals Account Receivable Report) lists outstanding amounts by proposal.