The four things terms should settle
When payment is due, stated as a period or a date rather than 'on receipt'. What is payable up front, if anything. How the client should reference the payment so you can match it. And what happens if it is late.
Each of those is one sentence. Together they remove the four conversations that otherwise happen after the due date, at which point you are negotiating from a weaker position than you were before you sent the invoice.
