International trade often requires banker’s acceptances, as well as even more formal arrangements. An exporter that requires even greater certainty of payment may request an irrevocable letter of credit. In this arrangement, the customer’s bank sends the exporter a letter stating that it has established a line of credit for the customer with a particular US bank. The exporter then can collect payment from the US bank before making the delivery. The US bank forwards the appropriate documents to the customer’s bank to receive reimbursement.