It’s common convention for customers to register in order to check out, but many customers want to skip that step. While this may involve some IT involvement to make it happen, you can always ask the customer to save their information in an account after the purchase has been made.
If you must require customers to register, make sure they know the benefits of doing so, such as the ability to see order history, track orders as they ship, save shipping addresses, etc. When putting messaging on the screen to this effect, be succinct but descriptive.
