| Michael Smoker Limited | Construction | 2006 |
| Mikina Engineering Limited | Manufacturing | 2003 |
| Milldown View Flat Management Company Limited | Real estate | 1986 |
| Miller Fencing Ltd | Construction | 2007 |
| Milnegate Homes (Christchurch) Limited | Construction | 2000 |
| Milton House (Bournemouth) Management Ltd. | Real estate | 2006 |
| Mindskills Limited | Extraterritorial | 2003 |
| Minstead Investments (Boscombe) Limited | Real estate | 2006 |
| Miracle Mane Ltd | Other services | 2022 |
| Miralago Limited | Real estate | 2021 |
| Mirelix Limited | Real estate | 1999 |
| Mission Systems Wimborne Limited | Manufacturing | 1934 |
| MJB Precision Engineering Limited | Manufacturing | 1996 |
| MKK Ltd | Professional & scientific | 2002 |
| Molas Integrated Limited | Information & communication | 2019 |
| Mondial Business Solutions Limited | Professional & scientific | 2005 |
| Monkey World Limited | Arts & recreation | 1990 |
| Monkton Wyld School Limited | Education | 1940 |
| Monsoon Indian Cuisine (Dorset) Limited | Hospitality | 2002 |
| Montpelier Europe Ltd | Professional & scientific | 2001 |
| Moon Light Indian Restaurant Ltd | Hospitality | 2017 |
| Mortgagetrace Limited | Financial services | 2004 |
| Moss Commercials Limited | Wholesale & retail | 2003 |
| Mosterton Village Stores Ltd | Wholesale & retail | 2021 |
| Motcombe Associate Developments Limited | Households | 2001 |
| Motcombe Garage Ltd | Wholesale & retail | 2003 |
| Motorhome Retrofits Ltd | Wholesale & retail | 2020 |
| Motors Fans and Pump Solutions Limited | Manufacturing | 2004 |
| MSB Education (UK) Limited | Education | 2004 |
| Msclara&E Ltd | Wholesale & retail | 2024 |
| MSL Oilfield Services Ltd | Manufacturing | 2006 |
| MTR Plumbing & Heating Limited | Construction | 2002 |
| MTW Ltd | Construction | 2005 |
| Muirhead Enterprises Limited | Hospitality | 2003 |
| Muncer Engineering Limited | Manufacturing | 1972 |
| Mungo Jerry International Limited | Information & communication | 1993 |
| Mungo Jerry Limited | Arts & recreation | 1972 |
| Mush Maintenance Ltd | Administrative & support | 2025 |
| N & N Services Limited | Manufacturing | 1997 |
| N J Harvey Building Contractor Limited | Construction | 2003 |
| N J Rodgers Ltd. | Arts & recreation | 2002 |
| N T Building Design Limited | Professional & scientific | 2003 |
| N-Tec Services Limited | Water & waste | 2005 |
| N.A. Williams Building Consultancy Limited | Professional & scientific | 2007 |
| N.C. Stansmore Limited | Real estate | 1971 |
| N.V. Austin Limited | Education | 2005 |
| Naana's Racing Limited | Professional & scientific | 2025 |
| Naanzaa Ltd | Hospitality | 2026 |
| Naude Limited | Real estate | 2007 |
| Navigator Properties Limited | Real estate | 1986 |
| Neale Design Services Limited | Information & communication | 1992 |
| Neatcross Limited | Manufacturing | 1981 |
| NET2BUSINESS IT Solutions Ltd | Information & communication | 2006 |
| Nethway House Management Company Limited | Households | 2003 |
| Network Building & Development Limited | Professional & scientific | 2002 |
| New Forest Bookbinding & Print Finishing Services Limited | Manufacturing | 1996 |
| New Forest Removals Ltd | Extraterritorial | 2006 |
| New Masterplanning Limited | Professional & scientific | 2006 |
| Newland Properties SW Limited | Real estate | 2004 |
| Newlec Electrical Contractors Ltd | Manufacturing | 1999 |
| NGS Consultants Ltd. | Information & communication | 1990 |
| Nice Ideas Consulting Limited | Professional & scientific | 2009 |
| Nicola Brookes Limited | Professional & scientific | 2004 |
| Nigel Whitefield Limited | Administrative & support | 2007 |
| Nightsabre Limited | Information & communication | 1996 |
| Nirorag Limited | Real estate | 2018 |
| NM Pensions Trustees Limited | Financial services | 2001 |
| North Dorset Disability Information Service (Norddis) | Information & communication | 2005 |
| Noutrix Ltd | Wholesale & retail | 2026 |
| NSN Properties Ltd. | Real estate | 2001 |
| NUB Theory Limited | Other services | 2020 |
| Nugent Plumbing and Heating Limited | Construction | 2006 |
| Number 3 Fitzharris Avenue Company Limited | Households | 1997 |
| Nutrastrada Ltd | Wholesale & retail | 2025 |
| O'Three Limited | Wholesale & retail | 1999 |
| Oaktower Limited | Construction | 1997 |
| Ocean Capital Ventures Limited | Administrative & support | 2007 |
| Ocean Development (Dorset) Limited | Wholesale & retail | 2003 |
| Odile Services Ltd | Health & social care | 2025 |
| Old Farm Court (Blandford) Management Limited | Extraterritorial | 1993 |
| Olliffe Plumbing & Heating Ltd | Construction | 2017 |
| Olympic Limited | Information & communication | 1995 |
| Onetechzone Ltd | Information & communication | 2023 |
| Online Prints Limited | Wholesale & retail | 2019 |
| Online Telematics Limited | Information & communication | 2000 |
| Optique 2000 Limited | Wholesale & retail | 2002 |
| Orchard Dairy Partnership | | 1993 |
| Orchard Watches Ltd | Other services | 2025 |
| Orion I.T. Limited | Information & communication | 2005 |
| Osbourne House Limited | Households | 2000 |
| Othniel Oysters Limited | Agriculture & fishing | 2006 |
| Othniel Shellfish Limited | Agriculture & fishing | 1993 |
| Otterbourne Management Company Limited | Households | 1985 |
| Otto Kampf Limited | Manufacturing | 2007 |
| Ottoman Dorset Ltd | Hospitality | 2025 |
| Otton Brothers Limited | Wholesale & retail | 1963 |
| Overcare Limited | Construction | 1988 |
| Overcliffe White House (Management) Co Limited | Households | 2000 |
| Owen Davies Properties Limited | Real estate | 1964 |
| Oxfords Bakery Limited | Manufacturing | 2003 |