When it comes to sending invoices to clients, it’s important to take into consideration your customer-base, as well as the image you would like to project. Generally speaking, larger companies will send an invoice at the end of the customer engagement while smaller companies or individuals practice the “due upon receipt” policy, having the invoice paid as soon as the transaction is complete.
Invoicing at the end of the engagement has a certain professionalism to it, and gives off the sense that the business is established. For larger companies, cash flow may be calculated by monthly goals, so getting paid immediately or two weeks later is relatively inconsequential. Small businesses or individuals often adopt this policy to project that established professionalism to their customers.
Having your invoice due upon receipt is a perfectly acceptable practice, as well. Most small companies or individuals would do well to use their size as an asset, as they are able to provide more attentive service to their customers than the big companies. That being said, most customers understand that immediate cash flow is essential to keeping smaller operations running smoothly.