I use a simple invoice that helps me to be paid immediately. Besides looking businesslike an invoice conveys a lot of information that Accounts Payable (A/P) departments need. If you give them the right details all at once, that will speed your payment.

1. Give accurate contact information, including your daytime phone number. Make sure the address is perfect so your payments don't go elsewhere.
2. For the invoice number, I use the date in numerical form, so 091224 for September 12, 2024 and add additional digits for the first invoice that day, the second invoice, and so on. So the third invoice on 091224 is 0912243. That's my own code, and you may want to use 091224-3, if that works best for you. Or something else, entirely.
3. Itemize the invoice and be sure there are no mathematical errors. I use an Excel spreadsheet which calculates the numbers automatically. You really look dumb if you submit an invoice that doesn't add up. Give as much or as little detail as the client is expecting. There's nothing wrong with sending an invoice that says, "Strategic Planning—$24,000," if that's what you have agreed in advance.
4. Include your Federal Tax ID if you have one, or if not, include your social security number.
5. Employers may want you to fill out a W-9 before they pay you. Filling out a W-9 is easy. Just provide your name and Social Security Number, or the name and Employer Identification Number of your business. By submitting a W-9, you are certifying that the tax identification number you are providing is correct and accurate and that you are not subject to backup withholding. When I'm asked for a W-9 I try to return it by fax within the hour. You can get a blank W-9 here: www.irs.gov/.
6. The Sample Invoice is linked as a PDF directly below the Google ads.