| MHK 1 Services Ltd | Construction | 2026 |
| Michelle Russell Consultancy Ltd | Professional & scientific | 2022 |
| Mickenna Hair Ltd | Other services | 2015 |
| Microbasix Ltd | Information & communication | 2017 |
| MID Street Properties Limited | Professional & scientific | 2012 |
| Midea Regeneration (Hong Kong) Limited | | 2009 |
| Midland Mallard Ltd | Transport & logistics | 2023 |
| Miha Auto Service Ltd | Wholesale & retail | 2022 |
| Mihfx Ltd | Information & communication | 2024 |
| Mike Parks (Consultancy) Limited | Information & communication | 2011 |
| Miles IP Consulting Ltd | Professional & scientific | 2026 |
| Mill Lodge Estates Limited | Real estate | 2009 |
| Mills Commercial Limited | Wholesale & retail | 1998 |
| Millview Associates Limited | Financial services | 2017 |
| Millway Associates Limited | Professional & scientific | 2010 |
| Millway Properties (Reigate) Limited | Real estate | 2023 |
| Miluan Ltd | Manufacturing | 2023 |
| Minadex Healthcare Ltd | Manufacturing | 2024 |
| Minato Sushi Ltd | Manufacturing | 2020 |
| Mindful Aesthetics Group Ltd | Health & social care | 2018 |
| Mindful Electrical Ltd | Construction | 2023 |
| Minutia Detailing Limited | Wholesale & retail | 2014 |
| Mitacron Limited | Professional & scientific | 2018 |
| Mixed Blessings, Brighton Ltd | Hospitality | 2023 |
| MJ Building Services (Brighton) Limited | Construction | 2006 |
| MJ Estimating Services Limited | Construction | 2024 |
| MJE Simpson Ltd | Health & social care | 2023 |
| Mjroc Limited | Hospitality | 2022 |
| MK 2023 Ltd | Real estate | 2023 |
| MK Roofing Contractors Ltd | Construction | 2016 |
| MM Property Portfolio 1 Limited | Real estate | 2019 |
| MM Property Portfolio 2 Limited | Real estate | 2020 |
| Mnlps (Operating) Limited | Transport & logistics | 2015 |
| Mnrecruit Ltd | Administrative & support | 2025 |
| Mobile Tyre Fitting Today Ltd | Manufacturing | 2026 |
| Modern Facades Construction Ltd | Construction | 2019 |
| Modern Nightingales Ltd | Health & social care | 2022 |
| Modular Power Limited | Professional & scientific | 2014 |
| Moffat Property Services Limited | Real estate | 1978 |
| Mohawk PSV Solutions Ltd | Wholesale & retail | 2020 |
| Moir Partners Limited | Professional & scientific | 2025 |
| Molly Transport Services Ltd | Transport & logistics | 2025 |
| Moment Associates Ltd | Professional & scientific | 2022 |
| Mondial Wine Limited | Wholesale & retail | 1985 |
| Monkey Events Limited | Other services | 2018 |
| Monkey GOD Media Ltd | Information & communication | 2019 |
| Monson General Store Limited | Wholesale & retail | 2024 |
| Monson Road Management Company Limited | Households | 2015 |
| Monument Group London Limited | Construction | 2023 |
| Moonbird Ltd | Information & communication | 2021 |
| Morganfield Consulting Limited | Information & communication | 2012 |
| Morr & Co LLP | | 2006 |
| Morrisons Core Services Limited | Administrative & support | 2011 |
| Morrisons Trustees Limited | Professional & scientific | 2012 |
| Morse Consulting Limited | Health & social care | 2007 |
| Mortimer Medical Ltd | Administrative & support | 2025 |
| Moss Build Ltd | Construction | 2011 |
| Motorvation (South East) Ltd | Wholesale & retail | 2015 |
| Mount Property Company Limited(The) | Real estate | 1984 |
| Mountain International Trading and Investments Limited | Information & communication | 2010 |
| MP4 YOU Ltd | Construction | 2014 |
| MR Catering Services Ltd | Hospitality | 2019 |
| Mrak Shops Ltd | Wholesale & retail | 2026 |
| MS Property Services Ltd | Construction | 2019 |
| MSY Design Ltd | Professional & scientific | 2023 |
| MT Technologies ZA Ltd | Professional & scientific | 2026 |
| Muddy Mindfulness C.I.C. | Education | 2024 |
| Mumma J'S Money Limited | Professional & scientific | 2024 |
| Munich Power Ltd | Wholesale & retail | 2019 |
| Munprop Limited | Households | 1982 |
| Munyaradzi Properties Limited | Hospitality | 2024 |
| Music Haven Limited | Information & communication | 2010 |
| Mutti Builders Ltd | Construction | 2022 |
| MV Project Media Ltd | Manufacturing | 2026 |
| MW Decorating Limited | Construction | 2019 |
| Mwilima Healthcare Service Limited | Health & social care | 2018 |
| MXK Academy Ltd | Administrative & support | 2017 |
| My Body Rocks Limited | Arts & recreation | 2024 |
| My Consulting and Advisory Services Limited | Professional & scientific | 2025 |
| My Meta Pet Craft Limited | Information & communication | 2022 |
| My Navy Limited | Wholesale & retail | 2026 |
| My New Venture Limited | Information & communication | 2026 |
| Mylas Magical Cleaning Ltd | Manufacturing | 2026 |
| Mymya Limited | Wholesale & retail | 2025 |
| Myosotis Training Limited | Other services | 2007 |
| Mystery Traders Ltd | Wholesale & retail | 2016 |
| Mytchett Residents Company Limited | Households | 2005 |
| N B Newland & SON Ltd | Construction | 2023 |
| N Equals 1 Ltd | Information & communication | 2025 |
| N.J. Richens Electrical Limited | Construction | 2010 |
| N.V. Building Services Ltd | Construction | 2023 |
| NA Cafe Limited | Hospitality | 2017 |
| Naked Diamonds Ltd | Manufacturing | 2005 |
| Naomi-Pearl Limited | Professional & scientific | 2018 |
| Natasha Hughes Tutoring Limited | Education | 2023 |
| National Utility Services Limited | Information & communication | 1979 |
| Natives Filmworks Limited | Information & communication | 2021 |
| Natural OIL Developments Limited | Real estate | 2025 |
| Naturally Talented ME CIC | Information & communication | 2020 |
| Nature-Wrap Ltd | Professional & scientific | 2019 |