| MSL Project Management Ltd | Construction | 2019 |
| MSS Property Rental Limited | Real estate | 2023 |
| MTS Marine Services Limited | Administrative & support | 2023 |
| Muba Services Limited | Real estate | 2020 |
| Muga Maldon Ltd | Education | 2024 |
| Mugilan Limited | Wholesale & retail | 2026 |
| Mull House Management Limited | Households | 2025 |
| Multi-User Credit Services Ltd | Financial services | 1983 |
| Multiseal Services Limited | Construction | 2008 |
| Multistruct Ltd | Construction | 2014 |
| Munoz Garcia UK Ltd | Transport & logistics | 2019 |
| Muraveika Limited | Construction | 2012 |
| Musical Moments (Europe) Limited | Information & communication | 1989 |
| Musical Moments Limited | Extraterritorial | 1983 |
| Muzzy Window Cleaning Ltd | Administrative & support | 2022 |
| Mwark Ltd | Arts & recreation | 2022 |
| MWH Dental Ceramics Limited | Health & social care | 2013 |
| My Chauffeur London Limited | Extraterritorial | 2009 |
| My Compliance Clinic Ltd | Administrative & support | 2023 |
| My Duty Clear Ltd | Transport & logistics | 2025 |
| My Medical PA Ltd | Administrative & support | 2017 |
| My Shop Solutions Limited | Construction | 2014 |
| My Training Online Ltd | Arts & recreation | 2025 |
| Mysons Group Holdings Ltd | Financial services | 2022 |
| N G Electrical Ltd | Construction | 2019 |
| N J M Futures Limited | Real estate | 1996 |
| N.C.C. Building & Civil Engineering Contractors Limited | Construction | 1994 |
| N.K.A Services Limited | Wholesale & retail | 2023 |
| N.S.D. Cladding Ltd | Construction | 2007 |
| Nabu & 3 Z Limited | Real estate | 2020 |
| Nanda Consulting Limited | Information & communication | 2012 |
| Nanorella Limited | Arts & recreation | 2025 |
| Narrell ANN Smith Limited | Extraterritorial | 2025 |
| Nathan Cronin Property Surveys Limited | Professional & scientific | 2023 |
| Nathanson LEE Ltd | Construction | 2019 |
| National Infrastructure Consultancy (NIC) Limited | Professional & scientific | 2021 |
| National Quality Care Solutions Limited | Health & social care | 2017 |
| Nature Radiance Company Limited | Manufacturing | 2024 |
| Natures Way Pest Control Ltd | Water & waste | 2019 |
| Naughty List Ltd | Information & communication | 2022 |
| Navillus Solutions Ltd | Administrative & support | 2024 |
| NB Accounting Services Limited | Professional & scientific | 2019 |
| Ncito Ltd | Administrative & support | 2010 |
| NE Raja Real Estates Ltd | Real estate | 2024 |
| Neighbour Scaffolding Ltd | Construction | 2024 |
| Nelowla Limited | Professional & scientific | 2021 |
| Nelson Anderson & Sons Limited | Extraterritorial | 1998 |
| Neolyfe Holdings UK Ltd | Administrative & support | 2025 |
| Nepsa Trade Windows Limited | Construction | 2019 |
| Neqsis Ltd | Information & communication | 2025 |
| Network 47 Limited | Wholesale & retail | 2013 |
| Nevendon Grange Management Company Limited | Real estate | 1996 |
| Nevendon Ltd | Hospitality | 2024 |
| New Golden Jade Ltd | Hospitality | 2018 |
| New Horizon Treasury & Trade Limited | Administrative & support | 2014 |
| New Property Ventures Ltd | Real estate | 2021 |
| Newhaven Solar Limited | Energy | 2011 |
| Newkem Industries Limited | Manufacturing | 2007 |
| Newlec Electrical Ltd | Construction | 2023 |
| Newlec Homes Ltd | Real estate | 2023 |
| Newline Roofing Services Ltd | Construction | 2025 |
| Newmont Capital Ltd | Information & communication | 2023 |
| Newport Estates (UK) Holdings Limited | Real estate | 2024 |
| Newport Estates (UK) Limited | Real estate | 2004 |
| Newport Estates Self Storage Limited | Real estate | 2025 |
| Newport Homes Limited | Construction | 2021 |
| NEX4TEK Ltd | Information & communication | 2025 |
| Next Step Academy Ltd | Arts & recreation | 2021 |
| Nextburj Ltd | Wholesale & retail | 2026 |
| Nexus Dance Initiative Ltd | Arts & recreation | 2025 |
| Nexus HR Consultancy Limited | Administrative & support | 2011 |
| Nexus Property Group Ltd | Real estate | 2016 |
| NH F&M Services Ltd | Construction | 2025 |
| NH Fire Holdings Ltd | Construction | 2025 |
| NH Fire Services (North) Ltd | Construction | 2025 |
| NH Fire Services Ltd | Construction | 2023 |
| NHT Management Limited | Professional & scientific | 2022 |
| Nicholls Valeting Services Ltd | Wholesale & retail | 2021 |
| Nick & IRA Ltd | Transport & logistics | 2015 |
| Nico Trans Logistic Ltd | Transport & logistics | 2025 |
| Nigel Hills Associates Ltd | Professional & scientific | 2025 |
| Nikrayji Limited | Real estate | 2023 |
| Nimbus Consultancy Ltd | Administrative & support | 2022 |
| Nini Solutions Limited | Information & communication | 2016 |
| Nirmalasom Ltd | Administrative & support | 2017 |
| Nisha Food and Wine Ltd | Other services | 2020 |
| Nixie Trades Ltd | Wholesale & retail | 2024 |
| NJC Audio Limited | Manufacturing | 2020 |
| Norfolk Solar Limited | Construction | 2008 |
| Norman Knights Group Limited | Financial services | 2020 |
| Norman Knights Limited | Manufacturing | 1974 |
| North Essex Speech and Language Therapy Services Ltd | Health & social care | 2023 |
| North Essex Therapy Services Limited | Health & social care | 2017 |
| North Road Trade Park Limited | Real estate | 2013 |
| Norwell Management LLP | | 2011 |
| Nottus Properties Limited | Real estate | 2004 |
| Nova Outdoor Living Ltd | Wholesale & retail | 2011 |
| Novaqc Limited | Information & communication | 2008 |
| Novita Subsidiaries | Professional & scientific | 1957 |
| NOW Move Home Ltd | Transport & logistics | 2020 |