| Mkamc Ltd | Information & communication | 2017 |
| MKF Capital Limited | Financial services | 2021 |
| MKM Agriculture Ltd | Agriculture & fishing | 2014 |
| Mkwines Limited | Wholesale & retail | 2015 |
| Mlocate Ltd | Real estate | 2020 |
| MLT Change Consulting Ltd | Professional & scientific | 2024 |
| Mlwr Ltd | Real estate | 2025 |
| MM HR Limited | Professional & scientific | 2010 |
| Mmma London Limited | Construction | 2026 |
| MNB Group Limited | Professional & scientific | 2016 |
| MNG Civils Ltd | Construction | 2022 |
| MOC Electrical Services Limited | Construction | 2017 |
| Mocha&Moon Ltd | Other services | 2024 |
| Modameta Limited | Information & communication | 2022 |
| Modeloe Ltd | Information & communication | 2018 |
| Modern Holdings Limited | Information & communication | 2021 |
| Modern Workplace Consulting Ltd | Administrative & support | 2018 |
| Modernism Ltd | Wholesale & retail | 2023 |
| Modular Building Developments Limited | Professional & scientific | 2018 |
| Module of Health Ltd | Other services | 2014 |
| Modus Capital Limited | Financial services | 2014 |
| Moe's Tech Services Ltd | Information & communication | 2019 |
| Mofb Ltd | Information & communication | 2026 |
| Mohns & Sanders Limited | Professional & scientific | 2004 |
| Mojibour Investments Limited | Professional & scientific | 2022 |
| Molerick Ltd | Professional & scientific | 2015 |
| Molifilms Entertainment Limited | Information & communication | 2012 |
| Moloud Limited | Extraterritorial | 2007 |
| Molteni Media Ltd | Information & communication | 2019 |
| Molyfit Wellness Ltd | Other services | 2021 |
| Momentum Data Ltd | Professional & scientific | 2017 |
| Momnific Ltd | Wholesale & retail | 2020 |
| Monarch Gate Residents Association Limited | Real estate | 2015 |
| Monarch KM 2 Limited | Health & social care | 2012 |
| Monarch Maintenance Group Ltd | Construction | 2026 |
| Monarchy Automotive Ltd | Administrative & support | 2016 |
| Monarchy Ltd | Professional & scientific | 2025 |
| Monastery Close Management Company Limited | Households | 1988 |
| Mondohost Ltd | Other services | 2022 |
| Monet Gardening Ltd | Administrative & support | 2023 |
| MONETA23 Limited | Real estate | 2023 |
| Money Unmuddled Limited | Administrative & support | 2025 |
| Monica Associates Limited | Professional & scientific | 2016 |
| Monk Property & Developments Limited | Construction | 2016 |
| Montant Limited | Information & communication | 2014 |
| Monteagle Management Company Limited | Administrative & support | 2003 |
| Monterey Ltd | Health & social care | 2025 |
| Monty Mason Asset Management Ltd | Real estate | 2016 |
| Moodsonic Ltd | Extraterritorial | 2019 |
| Moodsonic Services Ltd | Manufacturing | 2022 |
| Mooi by Wildcard Ltd | Other services | 2021 |
| Moonlight and Sleep Limited | Wholesale & retail | 2021 |
| Moonlight Books Limited | Information & communication | 2017 |
| Moonlight Organic Limited | Wholesale & retail | 2025 |
| Moonshiners Ltd | Other services | 2025 |
| Moore Social Consulting Ltd | Hospitality | 2025 |
| Moran Consulting Services Ltd | Information & communication | 2023 |
| Morchella Consulting Limited | Professional & scientific | 2024 |
| Moremi Limited | Information & communication | 2013 |
| Morena International Limited | Wholesale & retail | 2019 |
| Morgan Galbraith International Limited | Professional & scientific | 2003 |
| Morgan Howell Art Limited | Wholesale & retail | 2013 |
| Moritznet Ltd | Information & communication | 2019 |
| Morjaria Limited | Real estate | 2017 |
| Morny Limited | Manufacturing | 1994 |
| Morpheus AI Ltd | Information & communication | 2026 |
| Morris Jones Properties Limited | Real estate | 2019 |
| Morse Assets Limited | Households | 2024 |
| Mortgages in Lincoln Limited | Financial services | 2011 |
| Mortlach Limited | Professional & scientific | 2014 |
| Mortlake Heritage Limited | Real estate | 2021 |
| Mosquito Aircraft Museum Limited | Wholesale & retail | 2013 |
| Mossim Ltd | Professional & scientific | 2018 |
| MOT Cars Ltd | Wholesale & retail | 2026 |
| Mount Carmel Kindergarten Ltd | Health & social care | 2016 |
| Mountain Lodge Coaches Limited | Transport & logistics | 2013 |
| Mountain Valley Ltd | Wholesale & retail | 2011 |
| Mountfield Associates Limited | Information & communication | 2010 |
| Mountstars Technologies Limited | Information & communication | 2015 |
| Mouradian Family Games Limited | Wholesale & retail | 2023 |
| Move Inn Supplies Ltd | Wholesale & retail | 2018 |
| Moventus Limited | Real estate | 2016 |
| Movie Drivers Ltd | Transport & logistics | 2018 |
| Moçai Limited | Hospitality | 2025 |
| MP Angel LLP | | 2015 |
| MP Training and Consultancy Ltd | Professional & scientific | 2011 |
| MPC South Limited | Transport & logistics | 2023 |
| Mpjw Ltd | Professional & scientific | 2018 |
| Mpkuk Ltd | Manufacturing | 2019 |
| MPR Consulting Solutions Limited | Professional & scientific | 2017 |
| MPT Props Ltd | Information & communication | 2015 |
| MR Computer Limited | Wholesale & retail | 2014 |
| MR Fire Limited | Information & communication | 2015 |
| MR M Power Ltd | Construction | 2011 |
| MRA Global Supplies Limited | Wholesale & retail | 2024 |
| MRB Goalkeeping Limited | Arts & recreation | 2023 |
| MRG Productions Limited | Professional & scientific | 2021 |
| MRH Forecourts Limited | Real estate | 2004 |
| Mrpalamb Ltd | Information & communication | 2014 |
| MS Finpro Limited | Professional & scientific | 2024 |