| Montu Group UK Ltd | Wholesale & retail | 2022 |
| Montu Pharmaceutical Ltd | Wholesale & retail | 2023 |
| Montu UK Holdings Ltd | Health & social care | 2024 |
| Monwiz Group Ltd | Information & communication | 2020 |
| Moon Rise Group Limited | Construction | 2022 |
| Moores Motors Workshop Ltd | Wholesale & retail | 2023 |
| Mooti Wellness Ltd | Wholesale & retail | 2015 |
| Moove 28 Ltd | Professional & scientific | 2018 |
| Morgan Stanton Limited | Arts & recreation | 2025 |
| Morley Marketing Consultants Ltd | Information & communication | 2024 |
| Mornay Transport Limited | Transport & logistics | 2024 |
| Morris & SON Solutions Ltd | Administrative & support | 2026 |
| MOT City Garage Services Limited | Wholesale & retail | 2016 |
| Mother Luxe C.I.C. | Other services | 2025 |
| Motherson Technology Services United Kingdom Limited | Information & communication | 2020 |
| Motiv Events UK Limited | Professional & scientific | 2003 |
| Motorland Motors Ltd | Wholesale & retail | 2016 |
| Motorman World Ltd | Wholesale & retail | 2024 |
| Mountfield Property Management Limited | Professional & scientific | 2014 |
| Movie Guard Security Ltd | Administrative & support | 2011 |
| Mower Spares Direct Limited | Wholesale & retail | 2025 |
| Moyes Wealth Management Limited | Financial services | 2017 |
| MP and AP Properties LLP | | 2010 |
| MP Consultants (Berkshire) Ltd | Administrative & support | 2025 |
| MPM Matchpoint Marketing UK Ltd | Other services | 2026 |
| MPS Direct Ltd | Wholesale & retail | 2013 |
| MQ1 Consultancy Ltd | Information & communication | 2012 |
| MR & Sons Ltd | Construction | 2019 |
| MR Cable Communications Limited | Information & communication | 2015 |
| MR Cable Limited | Administrative & support | 2004 |
| MR Studio International UK Limited | Information & communication | 2025 |
| MRC Networking Ltd | Information & communication | 2024 |
| MRM Commercial Ltd | Construction | 2015 |
| MS Estate Group Limited | Real estate | 2022 |
| MS Licensed Events Ltd | Arts & recreation | 2020 |
| MS Live Productions Ltd | Arts & recreation | 2010 |
| MS Nosal Holdings Limited | Real estate | 2025 |
| MSG Nest Property Limited | Real estate | 2025 |
| MSH Consultancy Ltd | Professional & scientific | 2024 |
| MSP Talent Bridge Ltd | Administrative & support | 2009 |
| Muddy Duck Hospitality Ltd | Hospitality | 2025 |
| Muffin Affairs Limited | Hospitality | 2023 |
| Mulberry House Residents RTM Company Limited | Households | 2022 |
| Mulberry House Vets Limited | Professional & scientific | 2017 |
| Mulberry Lodge Limited | Construction | 2001 |
| Multichannel Consultancy Ltd | Professional & scientific | 2013 |
| Multichannel Customer Experience Ltd | Professional & scientific | 2014 |
| Mumbai Wokingham Ltd | Hospitality | 2020 |
| Mumbaiwalla Limited | Professional & scientific | 2021 |
| Murdoch Court Management Limited | Households | 1991 |
| MURSHAD804 Ltd | Transport & logistics | 2024 |
| Mvselected Ltd | Wholesale & retail | 2023 |
| Mwave Consulting Ltd | Professional & scientific | 2017 |
| MWD Healthcare Ltd | Health & social care | 2013 |
| Mwenya Limited | Health & social care | 2015 |
| My Best Interest Ltd | Wholesale & retail | 2024 |
| My Content Ltd | Information & communication | 2023 |
| My Golf Matters Ltd | Education | 2020 |
| My Little Boardroom Ltd | Other services | 2025 |
| My Little Eden Ltd | Wholesale & retail | 2022 |
| My Little Patisserie Ltd | Hospitality | 2012 |
| My School's Events Ltd | Information & communication | 2024 |
| My Team Hub Ltd | Information & communication | 2025 |
| Mycom Consulting Ltd | Professional & scientific | 2022 |
| Myhome-Lifestyles Limited | Administrative & support | 2023 |
| Mysa Care (Ardour) Limited | Other services | 2005 |
| Mysa Care (Blue Cedars) Limited | Health & social care | 2005 |
| Mysa Care (Holdco) Limited | Health & social care | 2022 |
| Mysa Care (Jasmine House) Limited | Health & social care | 2012 |
| Mysa Care (Tall Oaks) Limited | Health & social care | 1998 |
| Mysa Care (the Chestnuts Holdco) Limited | Health & social care | 2006 |
| Mysa Care (the Chestnuts) Limited | Health & social care | 1998 |
| Mysa Care and Support Limited | Financial services | 2008 |
| Mysa Care Supported Living Opco Limited | Health & social care | 2023 |
| Mysk Catering Ltd | Hospitality | 2020 |
| Mytkt Code Explorers Ltd | Information & communication | 2026 |
| Método Media Limited | Arts & recreation | 2025 |
| N Treacher Designs Limited | Administrative & support | 2002 |
| N.E.D SRL Limited | Transport & logistics | 2023 |
| N.G.L. Golf Consultancy Limited | Other services | 1979 |
| N.R.G. Distribution Limited | Administrative & support | 1995 |
| Nabhya Services Limited | Health & social care | 2016 |
| Nabi Production UK Ltd | Information & communication | 2020 |
| Nachammai Consultancy Limited | Information & communication | 2011 |
| Nadia Nizar Communications Limited | Information & communication | 2019 |
| Naga IT Solutions Ltd | Information & communication | 2021 |
| Nahal Investments Ltd | Real estate | 2024 |
| Namaskar Events Limited | Other services | 2011 |
| Nami Kohi Limited | Wholesale & retail | 2026 |
| Nandit Ltd | Wholesale & retail | 2025 |
| Nanna Fridays Limited | Health & social care | 2011 |
| Nanny Driver Ltd | Administrative & support | 2012 |
| Nanosurf UK Limited | Professional & scientific | 2020 |
| Narayan Computing Limited | Information & communication | 2018 |
| Narayan Growthbricks Limited | Real estate | 2024 |
| Narnia Development Limited | Construction | 2017 |
| National Energy System Operator Limited | Other services | 2017 |
| Nature's Genesis Ltd | Wholesale & retail | 2022 |
| Naughty Elephants Ltd | Professional & scientific | 2014 |
| Nautikey Limited | Professional & scientific | 2025 |