| MK24 Retails Ltd | Wholesale & retail | 2025 |
| MKC Entertainment Limited | Information & communication | 2022 |
| Mkdice Ltd | Hospitality | 2023 |
| MKM Accountancy Ltd | Professional & scientific | 2012 |
| MKM Payroll Ltd | Administrative & support | 2020 |
| MKO Supplies Ltd | Wholesale & retail | 2025 |
| Mkomw Groundworks Limited | Construction | 2014 |
| ML Eastleigh Ltd | Hospitality | 2024 |
| ML Plastering & Rendering Ltd | Construction | 2026 |
| MLG PAY Limited | Administrative & support | 2021 |
| MLG Trans Ltd | Transport & logistics | 2021 |
| MLK Paving Ltd | Construction | 2017 |
| Mmcon Limited | Construction | 2022 |
| Mmgt Homes Limited | Hospitality | 2023 |
| MMK Talent Ltd | Administrative & support | 2026 |
| Mmle Solutions Ltd | Professional & scientific | 2024 |
| Mmnfy Consultancy Ltd | Real estate | 2020 |
| Mmsub Ltd | Hospitality | 2022 |
| MMV Cargo Trading UK Ltd | Transport & logistics | 2024 |
| MNB Omnia Ltd | Real estate | 2026 |
| MNO Solutions Ltd | Professional & scientific | 2025 |
| MNR Plumbing Ltd | Construction | 2026 |
| MNS Waste Management Limited | Water & waste | 2014 |
| MO Rahman Real Estate Ltd | Real estate | 2025 |
| Mo-Link Travels Ltd | Wholesale & retail | 2025 |
| Mobile Flex Ltd | Wholesale & retail | 2025 |
| Mobile Mayhem Events Ltd | Administrative & support | 2026 |
| Mobile Molars Limited | Administrative & support | 2018 |
| Mobile World Portsmouth Limited | Other services | 2017 |
| Mobile World Repairs Ltd | Other services | 2025 |
| Moda Accessories Ltd | Wholesale & retail | 2017 |
| Modan Ltd | Hospitality | 2014 |
| Model Engineering Ltd | Professional & scientific | 2017 |
| Modern Software Leadership Ltd | Professional & scientific | 2025 |
| Modern World Ltd | Wholesale & retail | 2025 |
| Modernmak Ltd | Health & social care | 2024 |
| Modo Living Ltd | Wholesale & retail | 2026 |
| Moggeridge Carpentry Limited | Construction | 2007 |
| Mohib Locums Ltd | Wholesale & retail | 2024 |
| Mojacoo Ltd | Health & social care | 2019 |
| Molco Interiors Ltd | Construction | 2024 |
| Moling Experts Limited | Water & waste | 2024 |
| Moloff Technical Services Limited | Hospitality | 1996 |
| Momentum Joint Care Limited | Health & social care | 2025 |
| Momentum Management Solutions Limited | Professional & scientific | 2026 |
| MOMENTUM23 Ltd | Health & social care | 2020 |
| Monarch Computer Solutions Ltd | Information & communication | 2001 |
| Monas Grill Ltd | Hospitality | 2024 |
| Mondrian Mews Limited | Households | 2018 |
| Moneyfields Allotments & Gardens Association C.I.C. | Other services | 2012 |
| Moneyfields FC Ltd | Arts & recreation | 2019 |
| Moneyfields Sports & Social Club Limited | Arts & recreation | 2011 |
| Monkeys Bears and Bongos Limited | Real estate | 2025 |
| Monks Medical Imaging Ltd | Health & social care | 2026 |
| Mont Bravo Construction Ltd | Construction | 2024 |
| Mont Kiara Limited | Hospitality | 2025 |
| Montacute House (Management) Limited | Hospitality | 1988 |
| Montpelier Investments Limited | Professional & scientific | 2010 |
| Monty's TMI Ltd | Hospitality | 2019 |
| Moody Decking and Services Limited | Manufacturing | 2006 |
| Moodz Ltd | Professional & scientific | 2026 |
| Moontrak Limited | Manufacturing | 2016 |
| Moore and Cummings Motors Ltd | Wholesale & retail | 2019 |
| Moorelectrics Ltd | Construction | 2018 |
| Morbo Ltd | Arts & recreation | 2020 |
| More Than a Room Limited | Real estate | 2020 |
| More Than One Solution Ltd | Information & communication | 2017 |
| More-Jaki Ltd | Health & social care | 2011 |
| Mored Ltd | Information & communication | 2025 |
| Morested Ltd | Professional & scientific | 2019 |
| Morgan Ceilings and Partitions Limited | Construction | 2016 |
| Morgan Ibbs Group Limited | Construction | 2015 |
| Morgan Property Management Holdings Limited | Professional & scientific | 2022 |
| Morgan Property Management Limited | Real estate | 2018 |
| Morgar Services Ltd | Construction | 2019 |
| Moriah Family Support Group CIC | Health & social care | 2026 |
| Morpheustox Limited | Administrative & support | 2007 |
| Morris Crocker Limited | Professional & scientific | 1987 |
| Morrocan Halal Shop 2 Limited | Wholesale & retail | 2026 |
| Morscott 2007 Limited | Construction | 2007 |
| Morspace Construction Ltd | Construction | 2015 |
| Mortgage-Me Limited | Financial services | 2021 |
| Mortimer London Limited | Real estate | 2012 |
| Mosaic (Tristan) Limited | Manufacturing | 2006 |
| Mosaic Arts Collective Ltd | Arts & recreation | 2023 |
| Mosely Construction UK Limited | Administrative & support | 2010 |
| Mothers Pantry (Caroline) Ltd Limited | Hospitality | 2024 |
| Mothers Pantry Limited | Hospitality | 2022 |
| Motiff Ltd | Wholesale & retail | 2018 |
| Motion Mirror Ltd | Information & communication | 2025 |
| Motor House Trade Ltd | Wholesale & retail | 2018 |
| Motor Marketing Limited | Professional & scientific | 2014 |
| Motor Socials Ltd | Professional & scientific | 2020 |
| Moulin Court Southsea Limited | Hospitality | 2007 |
| Mountjoy Holdings Limited | Administrative & support | 2023 |
| Mountjoy Ltd | Administrative & support | 2006 |
| Mountsandel Limited | Education | 2020 |
| Mouse Properties Ltd | Real estate | 2014 |
| Move a Roost Limited | Extraterritorial | 2023 |
| Move in Meerkat Limited | Real estate | 2012 |