| Manor Gardens Investments Limited | Real estate | 2001 |
| Manor Hill Ceramics Limited | Construction | 2002 |
| Mario's Trattoria Limited | Real estate | 1987 |
| Maritime & Provincial Limited | Real estate | 1996 |
| Mark Jones Eyecare Ltd | Wholesale & retail | 2004 |
| Mark Mason Carpentry & Joinery Ltd | Construction | 2005 |
| Mark Paines Electrical Limited | Construction | 2004 |
| Marlborough Court (Salisbury) Management Limited | Professional & scientific | 1988 |
| Marlborough Tiles Holdings Limited | Manufacturing | 1946 |
| Marlborough Tiles Limited | Manufacturing | 2006 |
| Marmaris Kebab Van Limited | Wholesale & retail | 2017 |
| Marshgate Plant Limited | Administrative & support | 2006 |
| Martingate Corsham Ltd | Real estate | 2002 |
| Maurice Webb Property Investors Limited | Real estate | 2014 |
| MBM (Europe) Limited | Professional & scientific | 2000 |
| MC Administration Limited | Information & communication | 2008 |
| Mccloy (LS) Limited | Professional & scientific | 2002 |
| Measurement Supplies Limited | Transport & logistics | 1986 |
| Media Inventions Limited | Information & communication | 2002 |
| Media Plant Ltd | Administrative & support | 2006 |
| Melane Limited | Construction | 2005 |
| Melksham Business Services Limited | Professional & scientific | 1996 |
| Mensaco Limited | Professional & scientific | 1987 |
| Merchant Farmers Limited | Professional & scientific | 1964 |
| Metalwind Ltd | Professional & scientific | 1998 |
| Metdek Limited | Wholesale & retail | 1988 |
| Metoptic Systems Limited | Professional & scientific | 1989 |
| Microdisc Limited | Professional & scientific | 1974 |
| Middlecote Loft Conversions Limited | Construction | 2002 |
| Mike Horan Printing Limited | Manufacturing | 2006 |
| Mildreds Farm Services Limited | Households | 1994 |
| Millen Advice Point | Information & communication | 1999 |
| Miller Project Solutions Limited | Information & communication | 2007 |
| Mills (Textile Processors) Limited | Manufacturing | 1982 |
| Mindfulness Freedom Ltd | Education | 2019 |
| Mobilise GB Limited | Professional & scientific | 2008 |
| Molland Pools Limited | Wholesale & retail | 2005 |
| Montgomery Charles Financial Management Limited | Financial services | 1996 |
| Morris & Co. (Kidderminster) Limited | Manufacturing | 1960 |
| Morrisons Limited | Professional & scientific | 1988 |
| Morton Blane Limited | Professional & scientific | 2006 |
| Motega Designs Limited | Construction | 2003 |
| Mouland Decorating Limited | Construction | 2003 |
| Moving Point Limited | Professional & scientific | 2007 |
| Moxom Electrical Limited | Construction | 2003 |
| MRS (Building Contractors) Limited | | 1990 |
| Murphie and Murie Limited | Administrative & support | 2015 |
| N. Gentilcore Electrical Limited | Construction | 2003 |
| N. J. F. Online Services Limited | Information & communication | 1998 |
| Nail Soup Limited | Information & communication | 2005 |
| Naim Audio Limited | Manufacturing | 1973 |
| Negair Limited | Manufacturing | 2005 |
| Neil Rolls Building Services Limited | Construction | 2002 |
| Neon Management Limited | Professional & scientific | 2002 |
| Never Ending Fencing Limited | Construction | 2003 |
| Neville House (Swindon) Limited | Real estate | 2007 |
| New Business Builder | | 2001 |
| New Mark's Kitchen Limited | Hospitality | 2005 |
| NH Design (Lighting) Ltd | Information & communication | 2016 |
| Niche Recruitment Limited | Administrative & support | 2015 |
| Nichols Consulting Limited | Transport & logistics | 2005 |
| Nicola Jones & Co Limited | Professional & scientific | 2008 |
| Nicolas Trudgian Limited | Arts & recreation | 2002 |
| Nimrod Consulting Services Limited | Administrative & support | 2007 |
| Noble Consulting Ltd | Professional & scientific | 2005 |
| Nocturne Limited | Professional & scientific | 1999 |
| Noremarsh Software Solutions Limited | Professional & scientific | 2006 |
| Norman E. Webb (Holdings) Limited | Professional & scientific | 1998 |
| Northern Lights Fireworks Company Limited | Arts & recreation | 2000 |
| Nose in Front Ltd | Information & communication | 2005 |
| Novenco Building & Industry UK Ltd | Manufacturing | 2006 |
| Numensa Limited | Administrative & support | 2003 |
| Nutley Court (Burbage) Management Company Limited | Households | 1990 |
| O'Callaghan Tree Surgeons Limited | Agriculture & fishing | 2002 |
| Oakford Internet Services Limited | Information & communication | 2013 |
| Oakford Technology Limited | Information & communication | 2006 |
| Oaklodge Homes Wessex Ltd. | Construction | 1991 |
| Ockwells Plastering and Drylining Limited | Construction | 2005 |
| OKC Consultants Ltd | Professional & scientific | 2003 |
| Omega Derivatives Limited | Information & communication | 1994 |
| Oncet Associates Limited | Information & communication | 1995 |
| One Caring World Limited | Real estate | 1989 |
| Onustech Engineering Limited | Other services | 1977 |
| Ooma Limited | Manufacturing | 2002 |
| Opecfern Limited | | 1985 |
| Operations Management Research Limited | Professional & scientific | 2003 |
| Optica Limited | Information & communication | 1983 |
| Optikaswindon Limited | Wholesale & retail | 2006 |
| Orchard Trading Estate Management Limited | Real estate | 1987 |
| Osbourn & Sons Limited | Construction | 2006 |
| P & L Decorators Limited | Construction | 2003 |
| P I Mobile Vehicle Services Limited | Manufacturing | 2004 |
| P J Raynsford Limited | Construction | 2006 |
| P. R. Elletson & Co. Limited | Wholesale & retail | 2001 |
| P.D. North Limited | Other services | 2002 |
| P.R. Collins Landscapes Limited | Construction | 2007 |
| P.W.Dilloway Limited | | 1944 |
| PAN Fuel Ltd | Wholesale & retail | 2026 |
| Paradise Pets Limited | Wholesale & retail | 2000 |
| Parallel Designs Limited | Professional & scientific | 1994 |