| Name | Company Number | Date Appointed | Rating |
|---|---|---|---|
| G S S Sealand Ltd | 03169730 | 22/03/1996 | Dissolved |
| Manchester Tram Co Ltd | 04183241 | 04/12/2002 | Dissolved |
| Railtest Ltd | 03302974 | 04/12/2002 | Dissolved |
| Serco Aerospace Ltd | 02241383 | 24/02/1994 | Dissolved |
| Serco Merseyside Ltd | 04516383 | 04/12/2002 | Dissolved |
| Serco Nationwide Fire Services Ltd | 03306417 | 04/12/2002 | Dissolved |
| Serco Rail Services Ltd | 03119213 | 04/12/2002 | Dissolved |
| Strategic Support Management Ltd | 03720704 | 25/02/1999 | Dissolved |
| Tanker & Transport Service Co Ltd | 04222798 | 26/06/2001 | Dissolved |
| Name | Company Number | Date Appointed | Date Resigned | Rating |
|---|---|---|---|---|
| MERSEYRAIL SERVICES HOLDING COMPANY LIMITED | 04620520 | 06/01/2003 | 04/12/2003 | Silver |
| NORTHERN RAIL HOLDINGS LIMITED | 04007719 | 10/07/2000 | 23/09/2004 | Dissolved |
| NORTHERN RAIL LIMITED | 04619954 | 06/01/2003 | 23/09/2004 | Dissolved |
| Railtest Operations Ltd | 03318555 | 04/12/2002 | 05/03/2004 | Dissolved |
| SERCO CORPORATE SERVICES LIMITED | 04007730 | 10/07/2000 | 21/10/2003 | Not Trading |
| SERCO DOCKLANDS LIMITED | 03145194 | 04/12/2002 | 03/04/2003 | Dissolved |
| SERCO HOLDINGS LIMITED | 03970268 | 21/06/2000 | 03/12/2001 | Silver |
| SERCO INVESTMENTS LIMITED | 03287461 | 22/01/1998 | 10/06/2005 | Dissolved |
| Serco Operations Ltd | 01858592 | 10/10/1994 | 18/12/2002 | Dissolved |
| Serco Railtest Ltd | 03114741 | 04/12/2002 | 04/02/2004 | Dissolved |
| TRAFFIC INFORMATION SERVICES (TIS) HOLDINGS LIMITED | 04017593 | 29/05/2003 | 10/06/2005 | Dissolved |
| TRAFFIC INFORMATION SERVICES (TIS) LIMITED | 04017551 | 29/05/2003 | 10/06/2005 | Dissolved |
| TRAFFIC INFORMATION SERVICES (TIS) SECURITY LIMITED | 04071538 | 29/05/2003 | 10/06/2005 | Dissolved |