Question: When i am trying to add sample credit card number on my Sandbox Account on Vault getting below error.
here is request JSON
{
"number": "4769424246660779",
"type": "visa",
"expire\_month": 11,
"expire\_year": 2018,
"cvv2": "0123"
}

Response code: 400 Error response: {"name":"VALIDATION\_ERROR","debug\_id":"c7f1d5bd16eef","message":"Invalid request - see details","information\_link":"<https://developer.paypal.com/docs/api/#VALIDATION_ERROR>","details":[{"field":"number","issue":"Value is invalid"}]}

{"name":"VALIDATION\_ERROR","debug\_id":"c7f1d5bd16eef","message":"Invalid request - see details","information\_link":"<https://developer.paypal.com/docs/api/#VALIDATION_ERROR>","details":[{"field":"number","issue":"Value is invalid"}]}

Answer: 
Credit card numbers have an algorithm called Luhn Algorithm and your sample card number does not match with this calculation.

You may also check it online. <http://www.freeformatter.com/credit-card-number-generator-validator.html>
Here are some sample credit card numbers can be used for testing:

```
Visa: 4111111111111111
Visa: 4012888888881881
Visa: 4222222222222
JCB: 3530111333300000
JCB: 3566002020360505
JCB: 3088000000000009
MasterCard: 5555555555554444
MasterCard: 5105105105105100
MasterCard: 5500000000000004
American Express: 378282246310005
American Express: 371449635398431
American Express: 340000000000009 
American Express Corporate: 378734493671000
Australian BankCard: 5610591081018250
Diners Club: 30569309025904
Diners Club: 38520000023237
Diners Club: 30000000000004 
Discover: 6011111111111117
Discover: 6011000990139424
Discover: 6011000000000004 
Carte Blanche: 30000000000004

```