| Molton Campers Ltd | Wholesale & retail | 2026 |
| Monday Clicks Limited | Information & communication | 2015 |
| Mondrianie Design Services Ltd | Administrative & support | 2006 |
| Monkeymoos Castle Limited | Health & social care | 2019 |
| Monks Lane Valet Centre Ltd | Administrative & support | 2025 |
| Montano Aesthetics Limited | Other services | 2025 |
| Monty Bear Ltd | Information & communication | 2023 |
| Moonrakers Solar Ltd | Energy | 2022 |
| Moortown Farm Management Company Limited | Households | 1988 |
| Moosicology Limited | Education | 2010 |
| Moovana Logistics Ltd | Transport & logistics | 2025 |
| Moran Consulting Ltd | Professional & scientific | 2025 |
| Mordata Limited | Information & communication | 2012 |
| Morgan Electrical (South) Ltd | Construction | 2025 |
| Morning Holdings Limited | Financial services | 2023 |
| Morning Studio Ltd | Professional & scientific | 2021 |
| Moro Productions Ltd. | Arts & recreation | 2012 |
| Morrey Property Ltd | Real estate | 2025 |
| Morrisen Financial Services Ltd | Professional & scientific | 2023 |
| Morrison Express Corp. (U.K.) Limited | Transport & logistics | 2005 |
| Morse Street Developments Ltd | Real estate | 2017 |
| Morvan Investments Ltd | Administrative & support | 2013 |
| Morvan Trading Limited | Manufacturing | 1999 |
| Morwellham Properties Limited | Extraterritorial | 2006 |
| MOT Super Centre Limited | Wholesale & retail | 2004 |
| Motamedia Limited | Professional & scientific | 2007 |
| Motech Autocentres Ltd | Wholesale & retail | 2012 |
| Mothership Ventures Ltd | Wholesale & retail | 2025 |
| Motionlink Limited | Manufacturing | 2003 |
| Motorcycle Parts Worldwide UK Ltd | Wholesale & retail | 2024 |
| Mount Newtown Road (Management) Limited(The) | Households | 1978 |
| Mounthope Limited | Education | 2024 |
| Mourland Limited | Real estate | 2021 |
| Mousefield Family Farms Limited | Agriculture & fishing | 1973 |
| Move With TAY Ltd | Education | 2025 |
| Movedto Ltd | Information & communication | 2014 |
| Moving Forward Removals Ltd | Transport & logistics | 2022 |
| MR Simms Bath Ltd | Wholesale & retail | 2021 |
| MR Simms Cardiff Ltd | Wholesale & retail | 2025 |
| MR Simms Newbury Ltd | Wholesale & retail | 2021 |
| MR Simms ST Albans Limited | Wholesale & retail | 2023 |
| MRC Carpet and Flooring Limited | Construction | 2025 |
| MRL Enterprises Ltd | Construction | 2023 |
| Mrobertson Consulting Ltd | Professional & scientific | 2025 |
| MRS Wordsmith Group Limited | Information & communication | 2020 |
| MS Roofing Solutions Ltd | Construction | 2025 |
| MSC Consulting Limited | Professional & scientific | 2021 |
| MSG Scaffolding Ltd | Construction | 2023 |
| MT55 Consulting Ltd | Professional & scientific | 2023 |
| MUKONO3 Limited | Professional & scientific | 2011 |
| Mulberry House Management Company (Reading) Limited | Professional & scientific | 1987 |
| Mulhern Estates Limited | Real estate | 2004 |
| Mulhern Properties Limited | Construction | 1978 |
| Multiplex Internet Services Ltd | Information & communication | 2013 |
| Multipont Consulting Ltd | Professional & scientific | 2017 |
| Muniyal Properties Limited | Real estate | 2022 |
| Munzur Santo Limited | Manufacturing | 2025 |
| Murphycreations Ltd | Wholesale & retail | 2025 |
| Muse + Vale Ltd | Other services | 2026 |
| Musterannual Limited | Information & communication | 1987 |
| Mutimer UK Ltd | Wholesale & retail | 2025 |
| Muzla Transport Ltd | Transport & logistics | 2021 |
| Mvmt Mechanic Ltd | Health & social care | 2023 |
| MWB Consulting Limited | Health & social care | 2000 |
| MXP Software Solutions Ltd | Information & communication | 2026 |
| My Care Plus Ltd | Health & social care | 2019 |
| My Local Larder Limited | Wholesale & retail | 2021 |
| My Mighty Mind Limited | Education | 2018 |
| Myblueskydream Ltd | Construction | 2019 |
| Mydsl Ltd | Education | 2024 |
| Myguiltypleasureonline.Com Ltd | Wholesale & retail | 2018 |
| Mylivebook Limited | Information & communication | 2012 |
| Mynydd Y Gwynt Limited | Professional & scientific | 2002 |
| Myrtus Inspirations Limited | Other services | 2011 |
| Myservicesmadeeasy Ltd | Administrative & support | 2023 |
| Mythral Ltd | Real estate | 2026 |
| N & N Services Private Ltd | Transport & logistics | 2022 |
| N E W S Limited | Manufacturing | 1993 |
| N.W. Pennock Limited | Professional & scientific | 2001 |
| N2N Consult Limited | Information & communication | 2011 |
| NA Jackson Limited | Professional & scientific | 2017 |
| Naburn Partners Ltd | Professional & scientific | 2021 |
| NAD Home Instead Limited | Health & social care | 2022 |
| Nadia Balaghi Aesthetic Injections Ltd | Other services | 2023 |
| Nadia Property Management Ltd | Real estate | 2025 |
| Nala Works Limited | Other services | 2025 |
| Nalder Hill Heating Limited | Hospitality | 2015 |
| Nam-G Limited | Health & social care | 2017 |
| Nanini Limited | Professional & scientific | 2006 |
| Naomi Hall Design Limited | Other services | 2019 |
| Napenda Care Services Ltd | Health & social care | 2022 |
| Napier Capital Management Ltd | Real estate | 2009 |
| Nare Court Residents Company Limited | Real estate | 2005 |
| Natasha Jane Hair Limited | Other services | 2019 |
| Nathan Kubba Limited | Other services | 2019 |
| National Farm Research Unit Limited | Professional & scientific | 2015 |
| Nationwide Vehicle Services Ltd | Wholesale & retail | 2021 |
| Naturally-Inspired Limited | Information & communication | 2005 |
| Naturebureau Limited | Professional & scientific | 1989 |
| Navigator Paper UK Limited | Manufacturing | 1996 |