1. Ask for payment vouchers: ask the other company to provide payment vouchers, such as bank transfer records and telegraphic transfer vouchers, which can be used as a basis to confirm that the other party has paid and as a voucher for entry.
2. signing a contract: make sure that the rights and interests of both parties and the payment responsibilities are clearly stipulated in the contract for cooperative patent development, and indicate in the contract the method of recording in case the other party does not issue an invoice.
3. issue a receipt certificate: you can issue a receipt certificate yourself, record the specific amount and date of payment on it, and ask the other party to confirm and sign.