| MJ Abbott Properties Ltd | Real estate | 2025 |
| MJ ELM Ltd | Construction | 2022 |
| MJ Venture Property Ltd | Real estate | 2026 |
| MJH Executive Homes Limited | Construction | 2001 |
| MJH Homes Holdings Limited | Financial services | 2018 |
| MJH Homes Limited | Extraterritorial | 1993 |
| MJH Investments Limited | Real estate | 2001 |
| MJH Tax Ltd | Professional & scientific | 2013 |
| Mjmtb IT and Management Consultants Ltd | Information & communication | 2009 |
| MJP Portfolio 1 Ltd | Real estate | 2024 |
| MJW Kitchens and Bathrooms Limited | Construction | 2010 |
| MLA Training Solutions Ltd | Health & social care | 2024 |
| MLB Property Limited | Real estate | 2015 |
| Mlbry Investments LLP | | 2022 |
| MM Enviro Limited | Agriculture & fishing | 1993 |
| MM Handyman Services Limited | Construction | 2026 |
| MM Partners Ltd | Hospitality | 2025 |
| Mmcf Developments Ltd. | Real estate | 2019 |
| Mmcf Holdings Limited | Financial services | 2019 |
| MMO2 Limited | Information & communication | 2001 |
| MMS Accountants Limited | Professional & scientific | 2018 |
| Mmsy Limited | Hospitality | 2022 |
| Mnesic Ltd | Hospitality | 2025 |
| Mobile Ecosystem Forum Ltd | Information & communication | 2001 |
| Mobility Delivered Ltd | Wholesale & retail | 2019 |
| Mobinth Ltd | Professional & scientific | 2019 |
| Mocha Holdings Ltd | Financial services | 2020 |
| Mode Twentyone Ltd | Professional & scientific | 2021 |
| Modepact Limited | Households | 1987 |
| Modern Cave Properties Limited | Real estate | 2023 |
| Modern Life Construction Ltd | Construction | 2017 |
| Modernity Capital Limited | Financial services | 2021 |
| Modular Consultancy Ltd | Administrative & support | 2020 |
| Mod’S Barbers Ltd | Other services | 2025 |
| Mogen Business Hub Ltd | Information & communication | 2019 |
| Moggy Productions Limited | Arts & recreation | 2016 |
| Mojolake Limited | Professional & scientific | 2013 |
| Mokita Learning Ltd | Professional & scientific | 2023 |
| Mollie and FLO Ltd | Wholesale & retail | 2018 |
| Molokini Marketing Limited | Administrative & support | 2006 |
| Molpay International Ltd | Professional & scientific | 2017 |
| Molzac Limited | Construction | 2018 |
| Momentum Engineering Solutions Limited | Administrative & support | 2024 |
| Momentum Technology Limited | Manufacturing | 1996 |
| MON Concept Habitation UK Limited | Construction | 2019 |
| Monaghan Surveys Limited | Professional & scientific | 2008 |
| Monan Gozzett LLP | | 2019 |
| Monarch Rise Developments Ltd | Construction | 2025 |
| Monetaire (2014) Taxation Limited | Professional & scientific | 2012 |
| Monetaire 2017 Payroll Limited | Professional & scientific | 2013 |
| Monetaire Accountants Limited | Professional & scientific | 2014 |
| Monetaire Limited | Professional & scientific | 1999 |
| Monetaire Payroll Limited | Professional & scientific | 2004 |
| Monetaire Taxation Limited | Professional & scientific | 2006 |
| Moneymumofficial Limited | Administrative & support | 2021 |
| Monk Rawling Limited | Professional & scientific | 1989 |
| Monkwell Square Limited | Information & communication | 2024 |
| Monmer Foundry Limited | Extraterritorial | 1957 |
| Monoploy -1 Limited | Wholesale & retail | 2024 |
| Montague Ophthalmic Limited | Health & social care | 2008 |
| Montague Store Ltd | Wholesale & retail | 2016 |
| Montjoly Limited | Professional & scientific | 2023 |
| Moocari Limited | Hospitality | 2019 |
| Moon Labs AI Limited | Information & communication | 2023 |
| Moonz Ltd | Information & communication | 2026 |
| Moore Build Solutions Limited | Construction | 2025 |
| Moore Landscaping Ltd | Construction | 2025 |
| Moore Surfaces Ltd | Construction | 2021 |
| Moores Appliances Limited | Wholesale & retail | 2008 |
| Moorland House Limited | Health & social care | 2007 |
| Mooss Limited | Professional & scientific | 2022 |
| Moou Limited | Information & communication | 2022 |
| MOR Lettings Ltd | Real estate | 2022 |
| More Than a Thought Ltd | Public administration | 2025 |
| More Than Cleaning Limited | Administrative & support | 2017 |
| Moregood Property Limited | Real estate | 2020 |
| Moreobahealth Limited | Administrative & support | 2022 |
| Morgan & Horsfall Ltd | Wholesale & retail | 2022 |
| Morgan Harper-Brown Limited | Wholesale & retail | 2006 |
| Morgan Investment Group Limited | Financial services | 2025 |
| Morgan MC Carthy Associates Ltd | Wholesale & retail | 2013 |
| Morgisbord Media Ltd | Information & communication | 2017 |
| Moris Trading Ltd | Wholesale & retail | 2026 |
| Morridge Media Ltd | Arts & recreation | 2024 |
| Morrisseys Management Limited | Real estate | 2022 |
| Mortgage Pro Sussex Ltd | Financial services | 2022 |
| Mortgage Studio Ltd | Financial services | 2019 |
| Mortimer Clarke Solicitors Limited | Professional & scientific | 2007 |
| Mosaic Online Systems Holdings Limited | Professional & scientific | 2019 |
| Mosaic Online Systems Ltd | Information & communication | 2004 |
| Mosaic Share Holdings Limited | Extraterritorial | 2020 |
| Motion the Agency Ltd | Other services | 2022 |
| Motionhub Limited | Information & communication | 2025 |
| Motor International Ltd | Wholesale & retail | 2018 |
| Motorsense Bodyshop Limited | Wholesale & retail | 2026 |
| Mould Solve Ltd | Administrative & support | 2024 |
| Moullovi Ltd | Wholesale & retail | 2015 |
| Mountain Pass Limited | Professional & scientific | 2016 |
| Mousdell Close Freehold Ltd | Households | 2025 |
| Movara Property Group Ltd | Real estate | 2026 |