| Mooncat Ltd | Information & communication | 2014 |
| Mooney Plant Hire Limited | Construction | 2017 |
| Moonrakers Guest House Limited | Real estate | 1961 |
| Moonstone Counselling Ltd | Health & social care | 2021 |
| Moore Vehicle Solutions Ltd | Wholesale & retail | 2024 |
| More Bins Limited | Administrative & support | 2000 |
| Moreleigh Properties Limited | Real estate | 2012 |
| Morgan Brown Hair and Beauty Limited | Other services | 2016 |
| Morley Street Productions Ltd | Information & communication | 2011 |
| Morning Data Limited | Information & communication | 1992 |
| Morrish & Banham Ltd | Wholesale & retail | 2024 |
| Mortimer Design Limited | Professional & scientific | 2018 |
| Moses Survey Limited | Professional & scientific | 2010 |
| Mospar Ltd | Real estate | 2017 |
| Mosterton Developments Management Company (Dorset) Limited | Real estate | 2019 |
| Motley FIN Ltd | Hospitality | 2025 |
| Motorsparks Ltd | Manufacturing | 2012 |
| Mount Bina Holdings Limited | Arts & recreation | 2022 |
| Moura-Delort Ltd | Manufacturing | 2020 |
| Move-It Mortgages | | 2004 |
| Movement Research Limited | Professional & scientific | 1997 |
| Movement Tribe Limited | Education | 2021 |
| Moxey Associates Limited | Professional & scientific | 2019 |
| Moxey Builds Limited | Construction | 2020 |
| Moxham Properties Ltd | Real estate | 2024 |
| Moyses Stevens Landscapes & Gardens Limited | Administrative & support | 2009 |
| MR P Porter Limited | Health & social care | 2022 |
| MR Paul Porter Limited | Health & social care | 2008 |
| MS Europe Ltd | Administrative & support | 2002 |
| MSF Trades & Labour Ltd | Administrative & support | 2019 |
| Mslr Consulting Ltd | Information & communication | 2024 |
| MSU Dorchester Limited | Transport & logistics | 2016 |
| Mucha Limited | Professional & scientific | 1993 |
| MUD, Sweat and Gears Limited | Wholesale & retail | 2000 |
| Muirmcneil Limited | Information & communication | 2013 |
| Mullin Property Limited | Real estate | 2025 |
| Mure Liqueurs Ltd | Manufacturing | 2019 |
| Mutt Everything Dog Ltd | Wholesale & retail | 2025 |
| MVH Cleaning Ltd | Construction | 2026 |
| MW Carpet Care Limited | Administrative & support | 2023 |
| MW Mortgages Ltd | Financial services | 2021 |
| MX5 Heaven Limited | Wholesale & retail | 2015 |
| My Art Works Ltd | Arts & recreation | 2022 |
| My Home Solar Limited | Extraterritorial | 2022 |
| N & J Baker Ltd | Construction | 2013 |
| N & S Farming Limited | Agriculture & fishing | 2019 |
| N D K (Dorset) Limited | Construction | 2009 |
| N Whitley Ltd | Health & social care | 2023 |
| N.F.F. Precision Limited | Administrative & support | 1981 |
| N.G. Carpentry and Joinery Limited | Manufacturing | 2018 |
| Nadk Ltd | Health & social care | 2026 |
| Naga Strategic Consulting Limited | Other services | 2014 |
| Nagle Limited | Health & social care | 2020 |
| Nails by SAM Ltd | Other services | 2026 |
| Nanson Investments Ltd | Professional & scientific | 2012 |
| Napier Court Management Company (Dorchester) Limited | Households | 1985 |
| National Dental Limited | Professional & scientific | 2017 |
| Natterjack Publications Limited | Information & communication | 2004 |
| Nature Travels Ltd | Administrative & support | 2005 |
| Naturehire Property Management Company Limited | Real estate | 1991 |
| Nautica (Weymouth) Management Company Limited | Households | 2007 |
| Nazca | | 1994 |
| NBH Building & Construction Limited | Construction | 2011 |
| NCF Brickwork & Buildings Limited | Construction | 2018 |
| NEB Consulting (Property) Limited | Construction | 2010 |
| Nebula HRD Limited | Professional & scientific | 2016 |
| Needwood Engineering Consulting Limited | Professional & scientific | 2019 |
| Neil Prescott Developments Limited | Construction | 2003 |
| Nekhbet Ltd | Information & communication | 2024 |
| Netcetera UK Limited | Information & communication | 1997 |
| Nether Cerne Farms Limited | Agriculture & fishing | 1961 |
| Network H Limited | Professional & scientific | 2020 |
| Netzsch Pumps and Systems Limited | Manufacturing | 1989 |
| Neves Joinery & Construction Ltd | Construction | 2026 |
| New Barn Field Centre Limited | Education | 1993 |
| New Forest Chillout Limited | Hospitality | 2024 |
| New Frampton Court Limited | Households | 2005 |
| New Millennium Music Limited | Professional & scientific | 2023 |
| New Palace Ltd | Hospitality | 2013 |
| New Quay Shipyard Limited | Real estate | 1991 |
| Newburgh Networks Limited | Information & communication | 2014 |
| Newburn Court Limited | Real estate | 2004 |
| Newhouse Farm Partnership Limited | Construction | 2012 |
| Newman Farming Limited | Wholesale & retail | 2013 |
| Newman Services Group Ltd | Information & communication | 2018 |
| Newsflare Limited | Information & communication | 2011 |
| Newton Joinery Limited | Manufacturing | 2014 |
| Nexbridge Digital Ltd | Professional & scientific | 2025 |
| Next in Print Ltd | Wholesale & retail | 2025 |
| Next Level PUB Co Limited | Hospitality | 2025 |
| Next Step Racing Ltd | Arts & recreation | 2025 |
| Nexus Collaboration Management Company Limited | Households | 2020 |
| Niai Technologies Ltd | Information & communication | 2025 |
| Nician Limited | Construction | 2005 |
| Nikki's Little Play Café Ltd | Hospitality | 2023 |
| Ninas Nannies for Pets Limited | Other services | 2009 |
| Ninepin Limited | Information & communication | 2025 |
| Nisi Dominus Frustra Ltd | Real estate | 2022 |
| NJT Mechanics Ltd | Wholesale & retail | 2019 |
| NO. 5 Greenhill Management Limited | Households | 2004 |