The merchant provider typically charges a per-transaction fee for each credit card action.
If you have a physical store that accepts credit cards, you almost certainly have a merchant solution.
The ones that do offer online transactions give you access to a However, you can do some preliminary form validation work before talking to the payment gateway to save on transactions and transaction fees and possibly speed things for the user if they typed their credit card number incorrectly.
For more information on the upcoming change, we invite you to read our blog post.
The Luhn test is used by some credit card companies to distinguish valid credit card numbers from what could be a random selection of digits.
The checksum that is returned should match the one located on the website of the software developer.
However, if the main site gets hacked and a link is provided to a new download site and the checksum is changed on the website then you are basically being hoodwinked into downloading something you probably don't want to use.