| Mercury Commissioning Services Limited | Professional & scientific | 2004 |
| Meridian Health Arts Limited | Administrative & support | 2016 |
| Meridian Iliffe Limited | Professional & scientific | 2013 |
| Merlin Tools Limited | Wholesale & retail | 1998 |
| Metabond Limited | Information & communication | 2022 |
| Metalglide Doors & Windows Ltd | Manufacturing | 2025 |
| Meteon Limited | Information & communication | 2010 |
| MHQ Supplements Ltd | Arts & recreation | 2026 |
| Mid-Kent Contract Cleaning Services Ltd | Administrative & support | 2019 |
| Middleton PR Ltd | Professional & scientific | 2015 |
| Midland Caliper Centre Limited | Administrative & support | 2002 |
| Midle: Midlands Land Events CIC | Other services | 2023 |
| Mies International Limited | Transport & logistics | 1976 |
| Mies International Trustees Limited | Professional & scientific | 2023 |
| MIL Mental Health Limited | Health & social care | 2023 |
| Milvus Estates Ltd | Construction | 2024 |
| Ministry of Materials Ltd | Arts & recreation | 2021 |
| Minterm Services Ltd | Wholesale & retail | 2020 |
| Mintlink Labs Ltd | Information & communication | 2022 |
| Mintviz Ltd | Professional & scientific | 2015 |
| Miranda Transports Limited | Transport & logistics | 2023 |
| MJB Display Limited | Manufacturing | 2002 |
| MJB Promotions Ltd | Information & communication | 2020 |
| MJS Electrical Installations & Commissioning Limited | Manufacturing | 2015 |
| MLC Solutions Limited | Construction | 2013 |
| MLW Vaulted Limited | Financial services | 2026 |
| Mmam International Property Management Ltd | Real estate | 2019 |
| Modern Cloth Nappies Ltd | Wholesale & retail | 2019 |
| Moebius Systems Limited | Information & communication | 1990 |
| Mohican Holdings Limited | Health & social care | 2020 |
| Moiseyac Ltd | Manufacturing | 2016 |
| Mondaysuk Ltd | Other services | 2021 |
| Monk Education Associates Limited | Education | 2019 |
| Mooaba Ltd | Construction | 2025 |
| Moonshadows (Digital) Limited | Information & communication | 2013 |
| Moore Industrial Limited | Real estate | 2022 |
| Morgan-Fizer Ltd | Professional & scientific | 2018 |
| Mortgages-Online Limited | Financial services | 1997 |
| Motorway Surveys Limited | Professional & scientific | 2002 |
| Mouse (UK) Ltd | Information & communication | 2010 |
| Moving Currency Limited | Financial services | 2021 |
| MP Catering Ltd | Hospitality | 2018 |
| Mrajhart Limited | Professional & scientific | 2025 |
| MRB Financial Services Ltd | Professional & scientific | 2026 |
| Msan Ltd | Professional & scientific | 2013 |
| Msvl Ltd | Information & communication | 2015 |
| MTP 2018 Ltd | Wholesale & retail | 2018 |
| Muddy Boots Gifts Ltd | Wholesale & retail | 2014 |
| Mulholland Contractors Ltd | Manufacturing | 2016 |
| Mumsthatmove Ltd | Arts & recreation | 2026 |
| Murton Event Solutions Ltd | Transport & logistics | 2023 |
| Murton Logistics Ltd | Transport & logistics | 2020 |
| Mvrecon Limited | Information & communication | 2018 |
| MWE Business Consultancy Limited | Administrative & support | 2017 |
| My Boomerang Ltd | Information & communication | 2024 |
| Myeye Technology Limited | Information & communication | 2014 |
| Mylroi Rail Consulting Limited | Transport & logistics | 2019 |
| Nakasero Properties Limited | Real estate | 2013 |
| Naughty Hare Distillery Limited | Manufacturing | 2023 |
| Navigation Brewery Ltd | Hospitality | 2011 |
| NB Financial Risk Services Limited | Financial services | 2014 |
| NB Fire Protection and Services Ltd | Administrative & support | 2026 |
| Ncta Limited | Real estate | 2020 |
| Nest Architectural Ltd | Other services | 2021 |
| Nevarcian Limited | Information & communication | 2017 |
| New Ideas Infotech Ltd | Information & communication | 2021 |
| New Zealand Pump Company (Europe) Limited | Wholesale & retail | 2008 |
| Newlands Architectural Services Ltd | Professional & scientific | 2025 |
| Newtonic LLP | | 2021 |
| Next Step Solutions Group Limited | Wholesale & retail | 2023 |
| Nhkl 156 Ltd | Financial services | 2004 |
| Nice Spec Car Shop Limited | Administrative & support | 2016 |
| Nicky DOP Ltd | Information & communication | 2026 |
| Nikani Limited | Professional & scientific | 2022 |
| NINE700 Ltd | Professional & scientific | 2024 |
| Ninedales Limited | Real estate | 2024 |
| Ninety One Distribution Ltd | Wholesale & retail | 2024 |
| NJC Surveys Limited | Construction | 2006 |
| NM Joinery Design Limited | Construction | 2016 |
| NMS Consultancy Ltd | Professional & scientific | 2016 |
| Nnc-Breedon Ltd | Transport & logistics | 2019 |
| NOE Properties Limited | Real estate | 1995 |
| Norse Trade Ltd | Information & communication | 2018 |
| North Kent Plastics Limited | Extraterritorial | 2012 |
| Nottingham Symphonic Winds Production Limited | Arts & recreation | 2022 |
| Nova Lucis Limited | Professional & scientific | 2007 |
| NPH Homes Limited | Real estate | 2016 |
| Nrts Associates Limited | Professional & scientific | 2017 |
| Nu-Calgon EU Ltd | Extraterritorial | 2011 |
| Nuonano-Grwn Limited | Manufacturing | 2024 |
| Nuplace Property Limited | Real estate | 2014 |
| Nusic C.I.C. | Arts & recreation | 2016 |
| Nyati Holdings Limited | Administrative & support | 2012 |
| Nyumba Yako Limited | Real estate | 2019 |
| Oak Campervans Limited | Administrative & support | 2021 |
| Oakland Hotels Limited | Hospitality | 2010 |
| Oakmont Glazing Systems Ltd | Construction | 2021 |
| Oakmont Investment Group Ltd | Real estate | 2024 |
| Odyssian Limited | Professional & scientific | 2004 |
| Official Gifts Ltd | Professional & scientific | 2020 |