| Metcon Holidays Ltd | Administrative & support | 2022 |
| Metis Digital Limited | Other services | 2020 |
| Metric Designs Ltd. | Construction | 2008 |
| Metro Calibration Ltd | Professional & scientific | 2024 |
| Metron Consultancy Ltd | Professional & scientific | 2026 |
| Metropolis Capital Ltd | Financial services | 2010 |
| MG Drivers Club Limited | Other services | 2021 |
| Mhtek Limited | Information & communication | 2018 |
| MI Casa SU Casa Consulting Limited | Professional & scientific | 2015 |
| Michael Harrison and Company Limited | Administrative & support | 1979 |
| MID Ocean Consulting Limited | Professional & scientific | 2025 |
| Midges Property Limited | Real estate | 2021 |
| Mike Garrard Photography Limited | Professional & scientific | 2006 |
| Mikron Consultancy Services Ltd | Wholesale & retail | 2014 |
| Mikron Environmental Services Limited | Construction | 2008 |
| MIL LAB Ltd | Other services | 2026 |
| Miles Pulver Limited | Health & social care | 2014 |
| Miles's Holdings Ltd | Real estate | 2024 |
| Milky Way Galaxy Ltd | Health & social care | 2025 |
| Millar Ross Ltd | Professional & scientific | 2015 |
| Millennium Pharma Ltd | Wholesale & retail | 2021 |
| Millie Courtney Consulting Ltd | Professional & scientific | 2023 |
| Mimaoku Toys Ltd | Wholesale & retail | 2024 |
| Mindspire Labs Ltd | Information & communication | 2024 |
| Minimal Windows Limited | Wholesale & retail | 2010 |
| Misbourne Orchestra Limited | Arts & recreation | 2018 |
| Missenden Project Services Limited | Information & communication | 2013 |
| Mitass Ltd | Manufacturing | 2015 |
| Mizzen Construction, Heating & Plumbing Limited | Construction | 2016 |
| MKL Resources Limited | Administrative & support | 2011 |
| MM Consulting (London) Ltd | Professional & scientific | 2013 |
| MMB (London) Limited | Real estate | 2017 |
| MMJ AI Solutions Ltd | Information & communication | 2020 |
| Modele Investments Limited | Real estate | 2024 |
| Modus-O Ltd | Professional & scientific | 2014 |
| Mograph Manna Ltd | Information & communication | 2019 |
| Mohan Retail Ltd | Wholesale & retail | 2011 |
| Moksha Solutions Limited | Information & communication | 2013 |
| Molybdenum Industries Ltd | Wholesale & retail | 2025 |
| Monde Holdings Limited | Financial services | 2023 |
| Monetizationos Limited | Information & communication | 2024 |
| Monteblanco Turbos Limited | Wholesale & retail | 2019 |
| Moorpharm Consulting Ltd | Professional & scientific | 2021 |
| Moraya Limited | Information & communication | 2012 |
| More & More Design Ltd | Arts & recreation | 2008 |
| More Than Content Ltd | Information & communication | 2024 |
| Morgan Way Ltd | Real estate | 2018 |
| Morhaven Limited | Hospitality | 2026 |
| Morris & Forster Construction Ltd | Construction | 2025 |
| Moss Amersham Limited | Hospitality | 2016 |
| Motocross Maintenance Services Ltd | Education | 2010 |
| MOTORFINANCE-247 Ltd | Administrative & support | 2020 |
| Mouse EYE Investments Limited | Financial services | 2008 |
| Movement Art Design Experience Ltd | Arts & recreation | 2025 |
| Movement for Minds Limited | Arts & recreation | 2020 |
| Movement for Mums Limited | Arts & recreation | 2019 |
| Moyrahan Limited | Professional & scientific | 2023 |
| MPS Commercial Limited | Health & social care | 2013 |
| MR Lella Property Ltd | Real estate | 2020 |
| MR O Appliances Limited | Manufacturing | 2023 |
| MR Sample Ltd | Professional & scientific | 2009 |
| MR Smiles Ltd | Health & social care | 2023 |
| Mr.B Films Ltd | Information & communication | 2016 |
| Mrjm Holdings Ltd | Real estate | 2025 |
| MRL Tech Ltd | Information & communication | 2022 |
| Mrt&Associates Ltd | Health & social care | 2024 |
| MS & SS Enterprises Ltd | Real estate | 2023 |
| MSY World Ltd | Other services | 2023 |
| Muchloved Limited | Other services | 2023 |
| MUD Portage Productions Limited | Information & communication | 2019 |
| Mudb Holdings Limited | Real estate | 2017 |
| Muddy MTB Ltd | Arts & recreation | 2023 |
| Mulberry Landscaping Ltd | Administrative & support | 2013 |
| Muralyie Residencial Lets Ltd | Real estate | 2019 |
| Murray Rowlins Limited | Administrative & support | 1999 |
| Musicians UK Ltd | Arts & recreation | 2006 |
| Muungani Ltd | Other services | 2016 |
| MW Sports Enterprises Ltd | Other services | 2019 |
| MXL Consulting Limited | Professional & scientific | 2002 |
| MXL Property Ltd | Real estate | 2021 |
| My Dewine Ltd | Wholesale & retail | 2021 |
| My ZEN Studio Ltd | Information & communication | 2026 |
| Mybalance Fitness Ltd | Arts & recreation | 2018 |
| Mydigitallife Ltd | Information & communication | 2017 |
| Myriad Property Ltd | Real estate | 2021 |
| N Gillie Decorating Services Ltd | Construction | 2023 |
| N IT Consulting Ltd | Information & communication | 2014 |
| N.T Collins Investments Limited | Real estate | 2015 |
| N.T Collins Pipe Services Limited | Construction | 2014 |
| Nadine Ipoly Physiotherapy Ltd | Health & social care | 2025 |
| Nanfan Consultancy Services Ltd | Professional & scientific | 2020 |
| Nano Studio Limited | Information & communication | 2020 |
| Napier Capital General Partner NO 11 Limited | Administrative & support | 2008 |
| Napier Capital General Partner NO 13 Limited | Administrative & support | 2010 |
| Napier Capital NO.13 LP | | 2015 |
| Napier Capital Nominees NO 11 Limited | Professional & scientific | 2008 |
| Napier Capital Nominees NO 13 Limited | Professional & scientific | 2015 |
| NAS Healthcare Limited | Health & social care | 2012 |
| Natenac Limited | Information & communication | 2012 |
| Nationwide Copier Sales & Services Limited | Administrative & support | 2015 |