Mainly to ask the other party for an invoice. Before Charlesworth grinds, some companies need a contract to reimburse them. You should ask the company first, and then ask the polishing agency for invoices and contracts. It should also be noted that the determination of invoice content, taking Charlesworth's paper polishing as an example, can provide five kinds of polishing service fees, technical service fees and consulting service fees, and choose one of them. This mainly depends on the financial requirements of your unit first.