Project Mulla uses conventional HTTP response codes to indicate the success or failure of an API request. In general, codes in the 2xx range indicate success, codes in the 4xx range indicate an error that failed given the information provided failed validation (e.g. a required parameter was omitted, a charge failed, etc.), and codes in the 5xx range indicate an error with Project Mulla’s servers (these are seldom).
REFERENCE:
HTTP status code=>MPESA G2 API SOAP status code=> Description of the error
200 => 00 => The Request has been successfully received or the transaction has successfully completed.400 => 09 => The store number specified in the transaction could not be found. This happens if the Merchant Pay bill number was incorrectly captured during registration.400 => 10 => This occurs when the system is unable to resolve the credit account i.e the MSISDN provided isn’t registered on M-PESA400 => 30 => Returned when the request is missing reference ID400 => 31 => Returned when the request amount is Invalid or blank400 => 36 => Response given if incorrect credentials are provided in the request (incorrent merchant info)400 => 40 => Missing parameters400 => 41 => MSISDN(phone no.) is in incorrect format400 => 42 => Your PASSKEY, PAYBILL_NUMBER or environment variables may be incorrect401 => 32 => Returned when the account in the request hasn’t been activated. (unactivated)401 => 33 => Returned when the account hasn’t been approved to transact. (unapproved to transact)402 => 01 => Insufficient Funds on MSISDN account402 => 03 => Amount less than the minimum single transfer allowed on the system.402 => 04 => Amount more than the maximum single transfer amount allowed.402 => 08 => Balance would rise above the allowed maximum amount. This happens if the MSISDN has reached its maximum transaction limit for the day.409 => 43 => Duplicate merchant transaction ID detected409 => 35 => Response when a duplicate request is detected.409 => 12 => Message returned when the transaction details are different from original captured request details.409 => 99 => There's no recorded transaction associated with the transaction ID provided503 => 06 => Transaction could not be confirmed possibly due to confirm operation failure.503 => 11 => This message is returned when the system is unable to complete the transaction.503 => 34 => Returned when there is a request processing delay.503 => 29 => System Downtime message when the system is inaccessible.504 => 05 => Transaction expired in the instance where it wasn’t picked in time for processing.