| Monarch Security Services Ltd | Administrative & support | 2020 |
| Monarch Security Training Limited | Education | 2025 |
| Moneynotion Limited | Financial services | 1988 |
| Monibeautyshop Ltd | Wholesale & retail | 2024 |
| Monisha Beauty Limited | Other services | 2003 |
| Monk Investments Ltd | Construction | 2023 |
| Monk Property Services Limited | Construction | 2020 |
| Monkey VS OWL Limited | Construction | 2016 |
| Monmos 786 Limited | Hospitality | 2022 |
| Monmos Desserts Limited | Wholesale & retail | 2024 |
| Monmos Grill Limited | Hospitality | 2019 |
| Mono Design Limited | Arts & recreation | 2003 |
| Monster Communications Limited | Information & communication | 2010 |
| Monster Effects Ltd | Arts & recreation | 2026 |
| Montabery Ltd | Professional & scientific | 2026 |
| Montague Court Residents Management Company Limited | Households | 2016 |
| Montague Place (Clitheroe) Estate Management Company Limited | Households | 2021 |
| Montana Property Maintenance Ltd | Construction | 2017 |
| Monteath Management Ltd | Real estate | 2014 |
| Montenegro Limited | Real estate | 2012 |
| Monterno Furniture Contracts Ltd | Manufacturing | 2019 |
| Montessori on the Park Limited | Education | 2002 |
| Montgomerie Gardens (Clitheroe) Management Company Limited | Households | 2013 |
| Monti RK Ltd | Construction | 2025 |
| Montpelier Accountancy Limited | Professional & scientific | 2010 |
| Montrose Contract Services Limited | Transport & logistics | 2016 |
| Montrose Crystal Limited | Administrative & support | 2004 |
| Monument Five Ltd | Real estate | 2018 |
| Monument Four Ltd | Real estate | 2018 |
| Monument Seven Ltd | Real estate | 2018 |
| Monument SIX Ltd | Real estate | 2018 |
| Monument Three Ltd | Administrative & support | 2017 |
| MOO MOO Events Limited | Hospitality | 2022 |
| Mooney Engineering Services Ltd | Manufacturing | 2023 |
| Moongate Holdings Limited | Extraterritorial | 2025 |
| Moongate Property Investments Limited | Extraterritorial | 2025 |
| Moonlight Cottage Ltd | Wholesale & retail | 2024 |
| Moonrise Trade Ltd | Wholesale & retail | 2024 |
| Moonsha Delight Limited | Hospitality | 2025 |
| Moonshi Ltd | Wholesale & retail | 2022 |
| Moonshine Motors Limited | Extraterritorial | 2020 |
| Moonshot International Limited | Financial services | 2017 |
| Moor Joinery (Derby) Ltd | Construction | 2009 |
| Moor Street Development Management Company Limited | Households | 2006 |
| Moorgate Management Limited | Professional & scientific | 2011 |
| Moorhead Properties Ltd. | Real estate | 1998 |
| Moorland Consulting Limited | Professional & scientific | 2016 |
| Moorland Poultry Limited | Agriculture & fishing | 1987 |
| Moorways Training Solutions Ltd | Manufacturing | 2024 |
| MOR Property Ltd | Real estate | 2018 |
| Moraine Holdings Limited | Administrative & support | 2019 |
| Moran Commercials Ltd | Administrative & support | 2013 |
| Moran Homes Group Ltd | Financial services | 2026 |
| Moran Logistics (Ambient) Ltd | Transport & logistics | 2024 |
| Moran Ltd | Extraterritorial | 2009 |
| Moran Solutions Ltd | Extraterritorial | 2012 |
| Morchid & Co Ltd | Professional & scientific | 2017 |
| More Life Anglesey Limited | Hospitality | 2024 |
| More Life Enterprises Limited | Hospitality | 2023 |
| More Passport Stamps Ltd | Information & communication | 2018 |
| More Than Digital Ltd | Professional & scientific | 2019 |
| More Violet Ltd | Professional & scientific | 2026 |
| Morecroft Electrical Group Holdings Ltd | Financial services | 2024 |
| Morecroft Electrical Group Limited | Construction | 2019 |
| Morecroft Electrical Ltd | Construction | 2004 |
| Morecroft Holdings Ltd | Administrative & support | 2015 |
| Morefeel Limited | Hospitality | 2023 |
| Moreray Ltd | Professional & scientific | 2024 |
| Morewood Payroll Services Ltd | Professional & scientific | 2020 |
| Morgan Carter Investment 1 Limited | Real estate | 2026 |
| Morgan Industrial Properties Limited | Construction | 1986 |
| Morgan Pidcock Properties Ltd | Real estate | 2014 |
| Morgan Sinclair Limited | Construction | 2021 |
| Morgantech Services Ltd | Information & communication | 2025 |
| Moriah White Ltd | Health & social care | 2015 |
| Morley Construction Services Limited | Construction | 2018 |
| Morley Group Holdings Ltd | Financial services | 2026 |
| Morley Holland Holdings Ltd | Real estate | 2021 |
| Morley Plumbing Services Limited | Construction | 2015 |
| Morley Victoria Limited | Real estate | 2025 |
| Morning Rise Supported Housing Limited | Health & social care | 2009 |
| Mornington Court Management (Derby) Limited | Professional & scientific | 1996 |
| Morrell Floor Systems Ltd | Construction | 2015 |
| Morrell Property Holdings Ltd | Real estate | 2026 |
| Morrellos Property Management Limited | Real estate | 2020 |
| Morris and MEE Limited | Construction | 2007 |
| Morris Minor Enthusiasts Club Limited | Professional & scientific | 2019 |
| Morris Minor Owners and Enthusiasts Club Limited | Professional & scientific | 2019 |
| Morris Minor Owners Club Limited | Other services | 1980 |
| Morris Motors Limited | Extraterritorial | 1990 |
| Morrison (Builders & Contractors) Limited | | 1981 |
| Morrison Design Holdings Limited | Financial services | 2018 |
| Morrison Design Limited | Professional & scientific | 1986 |
| Morrissey Actuarial Development Limited | Professional & scientific | 2020 |
| Mortgage Advice Bureau (Bristol) Ltd | Extraterritorial | 2012 |
| Mortgage Advice Bureau (Derby) Limited | Financial services | 2006 |
| Mortgage Advice Bureau (Holdings) PLC | Professional & scientific | 2000 |
| Mortgage Advice Bureau (UK) Limited | Extraterritorial | 2006 |
| Mortgage Advice Bureau Limited | Financial services | 1997 |
| Mortgage and Finance Arena Limited | Administrative & support | 2015 |