Obviously a lot of sites do format credit card numbers, but keep in mind that does add an additional level of complexity because you have to verify the type of

Obviously a lot of sites do format credit card numbers, but keep in mind that does add an additional level of complexity because you have to verify the type of card and what formatting to perform. American Express uses 15 digit numbers grouped in 4-6-5 format, so if you accept AMEX, you have to take that into account.