Some sites demand credit card numbers for registration although payment is not required. In order to complete such registrations, i have posted some sample credit card numbers which i obtained from http://doc.async.com.br/formcheck_re/ccnums.html. Credit card numbers are not random. They can be checked by a mathematical formula for validity. Each kind of credit card uses a slightly different rule.
Following are the sample numbers for various providers.
| Credit Card | Sample Number |
| Visa | 4111 1111 1111 1111 |
| MasterCard | 5500 0000 0000 0004 |
| American Express | 3400 0000 0000 009 |
| Diner’s Club | 3000 0000 0000 04 |
| Carte Blanche | 3000 0000 0000 04 |
| Discover | 6011 0000 0000 0004 |
| en Route | 2014 0000 0000 009 |
| JCB | 3088 0000 0000 0009 |
