a request to supply goods (sent by the customer)
a letter where the customer tries to get better terms
the price given for goods or a piece of work
a letter saying you are not satisfied about something
a document that proves you have paid for some goods
a letter to a customer about an unpaid invoice
a bill for goods sent or work done
a list of amounts paid and still owed, sent every month
an approximate calculation of the cost of something
a request for information (sent by the customer)