| SIP response | Cause value |
| 400 Bad request | 0x29 41 Temporary failure |
| 401 Unauthorized | 0x15 21 Call rejected |
| 402 Payment required | 0x15 21 Call rejected |
| 403 Forbidden | 0x15 21 Call rejected |
| 404 Not found | 0x01 1 Unallocated number |
| 405 Method not allowed | 0x3f 63 Service unavail. unspecified |
| 406 Not acceptable | 0x4f 79 Service not implemented |
| 407 Proxy Authentication required | 0x15 21 Call rejected |
| 408 Request timeout | 0x66 102 Recovery on timer expiry |
| 410 Gone | 0x16 22 Number changed |
| 413 Request entity too large | 0x7f 127 Interworking, unspecified |
| 414 Request-URI too long | 0x7f 127 Interworking, unspecified |
| 415 Unsupported media type | 0x4f 79 Service or option not implemented |
| 416 Unsupported URI scheme | 0x7f 127 Interworking, unspecified |
| 420 Bad extension | 0x7f 127 Interworking, unspecified |
| 421 Extension required | 0x7f 127 Interworking, unspecified |
| 423 Interval too brief | 0x7f 127 Interworking, unspecified |
| 480 Temporarily unavailable | 0x12 18 No user responding |
| 481 Call/transaction does not exist | 0x29 41 Temporary failure |
| 482 Loop detected | 0x19 25 Exchange routing error |
| 483 Too many hops | 0x19 25 Exchange routing error |
| 484 Address incomplete | 0x1c 28 Invalid number format |
| 485 Ambiguous | 0x01 1 Unallocated Number |
| 486 Busy here | 0x11 17 User busy |
| 487 Request terminated | 0x1f 31 Call cleared |
| 488 Not Acceptable Here | 0x41 65 Bearer cap. not implemented |
| 500 Server internal error | 0x29 41 Temporary failure |
| 501 Not implemented | 0x4f 79 Service not implemented |
| 502 Bad gateway | 0x26 38 Network out of order |
| 503 Service unavailable | 0x29 41 Temporary failure |
| 504 Gateway time-out | 0x66 102 Recovery on timer expiry |
| 505 Version not supported | 0x7f 127 Interworking, unspecified |
| 513 Message too large | 0x7f 127 Interworking, unspecified |
| 600 Busy everywhere | 0x11 17 User busy |
| 603 Decline | 0x15 21 Call rejected |
| 604 Does not exist anywhere | 0x01 1 Unallocated number |
| 606 Not acceptable | 0x41 65 Bearer cap. not implemented |
