Across from where you put the recipient's name and contact info, include the details of your invoice. This placement makes it easy to keep track of vital information — for both you and the recipient. You'll want to include: Invoice Number, Date prepared, Payment due date.
Generally, your contact info should be on the opposite side of the recipient's info. So if your business name and logo are on the right side of the invoice at the top, the client's name and info should be below this on the left side.