| Miles & Co. Events Ltd | Administrative & support | 2014 |
| Miles & Co. Holdings Ltd | Financial services | 2020 |
| Millers of Southsea Ltd | Other services | 2012 |
| Mills Consultancy Ltd | Real estate | 2007 |
| Milton Village Property Limited | Real estate | 2020 |
| Milton Wentworth Limited | Real estate | 2000 |
| Minglanibrothers Limited | Hospitality | 2025 |
| Minimocs Limited | Wholesale & retail | 2024 |
| Miniyethu Ltd | Health & social care | 2014 |
| Minoo Property Rental Ltd | Households | 2023 |
| Mirotel Ltd | Information & communication | 2014 |
| Miss Maleeha Limited | Professional & scientific | 2016 |
| Mission Ready Developments Ltd | Wholesale & retail | 2025 |
| Mitchell Clow Limited | Professional & scientific | 2015 |
| MJ Hoist Solutions Ltd | Manufacturing | 2019 |
| MJ Wealth Ltd | Professional & scientific | 2021 |
| MJD Financials Ltd | Financial services | 2015 |
| Mkmo Interim Solutions Ltd | Professional & scientific | 2025 |
| MKS (UK) Limited | Professional & scientific | 2014 |
| MKS Estates Limited | Extraterritorial | 2014 |
| MKS Health Limited | Extraterritorial | 2014 |
| MMP Efirb Limited | Administrative & support | 2021 |
| MNK Property Group Ltd | Real estate | 2025 |
| Mo:Mos Inc. Limited | Hospitality | 2025 |
| Mobile Fuel Assist Ltd | Wholesale & retail | 2024 |
| Moir-Brown Limited | Administrative & support | 2022 |
| Monks Holdings Limited | Administrative & support | 2020 |
| Monolith Resources Ltd | Construction | 2023 |
| Monu Valley Ltd | Hospitality | 2023 |
| Moore Property Limited | Real estate | 2017 |
| Morelife Project Ltd | Information & communication | 2025 |
| Moreton Property Services Ltd | Households | 2025 |
| Moreton Property South Ltd | Households | 2025 |
| Morgan Flats NO.2 Limited | Households | 2002 |
| Morph PR and Marketing Ltd | Professional & scientific | 2008 |
| Mortec Ltd | Professional & scientific | 2023 |
| MOTIV8 South Ltd | Health & social care | 1998 |
| Motorev Ltd | Wholesale & retail | 2023 |
| Motorscope Limited | Extraterritorial | 1989 |
| Mount Audio Ltd. | Information & communication | 2015 |
| Mountbatten Management Company Limited | Households | 2017 |
| MPC Seminars Ltd | Health & social care | 2024 |
| Mrcg Ltd | Real estate | 2018 |
| MRS Marigold Property Services Ltd | Real estate | 2020 |
| MS Media House Ltd | Education | 2019 |
| MS P the Unicorn and Friends Limited | Arts & recreation | 2019 |
| MSA Solent Limited | Hospitality | 2025 |
| Msmk Engineering Ltd | Manufacturing | 2014 |
| Mstrad Limited | Construction | 2007 |
| Mubi Cleaning Solution Ltd | Administrative & support | 2023 |
| Mumbai 39 Limited | Hospitality | 2022 |
| Mumms Cafe Ltd | Real estate | 2019 |
| Murphy Large Limited | Wholesale & retail | 2016 |
| Musson Services Builders Ltd | Construction | 2003 |
| Must Shot Media Limited | Information & communication | 2025 |
| Mxsro Limited | Construction | 2022 |
| My Car Cleaner Ltd | Wholesale & retail | 2017 |
| My New Canvas C.I.C. | Hospitality | 2014 |
| My Own Tutor MK Ltd | Education | 2021 |
| My Sunshine Limited | Hospitality | 2025 |
| Myhomeclean Ltd | Administrative & support | 2020 |
| Mynrd Ltd | Professional & scientific | 2026 |
| N & L Eaton Estates (ST Ives) Ltd | Households | 2022 |
| N & M Dele Limited | Wholesale & retail | 2015 |
| N D J Carpentry Services Ltd | Construction | 2021 |
| N L Hang Property Ltd | Hospitality | 2017 |
| N2A Wireless Limited | Information & communication | 2023 |
| Nadia Holdaway UK Ltd | Other services | 2023 |
| Nadine DI Donato & Co Ltd | Health & social care | 2019 |
| Nana K & T Executive Transport Group Ltd | Transport & logistics | 2026 |
| Nand Software Development Ltd | Information & communication | 2021 |
| Nanthu Limited | Real estate | 2022 |
| NAP Construction AH Limited | Administrative & support | 2009 |
| NAP Construction NJ Limited | Administrative & support | 2009 |
| NAP Construction PC Limited | Administrative & support | 2009 |
| Nasta Pani Ltd | Hospitality | 2023 |
| Nation Removals Ltd | Transport & logistics | 2025 |
| Nationalpm Ltd | Construction | 2026 |
| Natty's Ltd | Hospitality | 2019 |
| Naturally Beautiful Hair Ltd | Other services | 2012 |
| Nautical Archaeology Society(The) | Professional & scientific | 1972 |
| Navaro Properties Limited | Real estate | 2022 |
| Naykyar Residentials Limited | Real estate | 2026 |
| NCH Windows Ltd | Construction | 2019 |
| NDS Electrical Services Limited | Construction | 2006 |
| Nedwards Ltd | Hospitality | 2017 |
| Negotia Business Consulting Limited | Professional & scientific | 2026 |
| Negotia Ltd | Administrative & support | 2023 |
| Nemesis Fire Ltd | Professional & scientific | 2024 |
| Neovrix Solutions Ltd | Administrative & support | 2026 |
| Nereus Engineering Ltd | Manufacturing | 2026 |
| Nesbits Auctions Limited | Wholesale & retail | 2013 |
| Netley Limited | Hospitality | 2012 |
| Netley Mansions Management Company Limited | Households | 1967 |
| Netus Limited | Information & communication | 2014 |
| Network-Rsd Consultancy Ltd | Manufacturing | 2014 |
| Neue Skin Limited | Arts & recreation | 2012 |
| Neutrix Hub Ltd | Education | 2026 |
| New Leaf Lyme Support & Publishing CIC | Information & communication | 2025 |
| New on Here Ltd | Hospitality | 2026 |