After hitting Send Invoice, you’ll see a box labeled “Your Message” in “Send Invoice” panel. This is a good place to thank your client for the project and suggest preferred payment methods. Type whatever you like, then hit the Send Invoice button when you’re done.
You can also set up a standard invoice greeting that will appear in the “Send Invoice” panel by default. To do this, click on Settings at the top of the page, then Invoice Templates in the sidebar on the right. Type your message into the Invoice Greeting box and hit Save Settings.