An invoice and a bill are usually the same document seen from two sides. The seller issues an invoice to request payment; the buyer receives it as a bill to pay. The paper is identical — the word just depends on who is holding it.
The same document, two viewpoints
When you send a client a request for payment, you call it an invoice. To that client it is a bill they owe. In accounting the same document sits in your accounts receivable (money owed to you) and in their accounts payable (money they owe).
Why the words differ
“Invoice” is the formal, business-to-business term and implies an itemised document with an invoice number, dates and payment terms. “Bill” is the everyday word, used for things you pay immediately or on receipt — a restaurant bill, a utility bill, a phone bill.
Which should your document say?
If you are a freelancer or business asking a client to pay, label it Invoice. It reads as professional, it is what accounting software and clients expect, and it carries the detail (number, due date, tax) that a plain “bill” often lacks.
Invoice, bill, receipt — don’t mix them up
An invoice/bill requests payment; a receipt confirms payment after it is made. So you send an invoice, the client pays the bill, and you issue a receipt as proof.
Create a professional invoice free — no account needed.