An invoice is a request for payment to a client or customer after a product or service is delivered. It is usually due within 30 to 90 days (about three months) after an invoice is issued and is used to record sales on account. In contrast, a bill is an invoice to vendors to request a payment due immediately and is used to record purchases on account. Unless otherwise there is an agreement between the business and the customer after the customer's order is completed, Invoices should be sent immediately to keep the cash flow consistent and the growth of the business.

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