| Mortgage Broker Media Limited | Administrative & support | 2021 |
| Mortgage Street Ltd | Financial services | 2022 |
| Mortgages Made Simple Holdings Ltd | Financial services | 2025 |
| Mortgages Made Simple Limited | Financial services | 2014 |
| Mosaic Cloud Services Limited | Information & communication | 2008 |
| Mosaic Digital Media Limited | Information & communication | 2016 |
| Mosaic Software Solutions Ltd | Administrative & support | 2026 |
| Mosley Street Ventures Limited | Construction | 2007 |
| Moss HR Consulting Limited | Professional & scientific | 2017 |
| Moss Tech Consulting Ltd | Information & communication | 2017 |
| Moss Warne Limited | Financial services | 2023 |
| Motacraft Engineering Limited | Extraterritorial | 1977 |
| Mote Hill Court (Church Street) Limited | Professional & scientific | 2002 |
| Mother Espresso Limited | Hospitality | 2017 |
| Mothers Heart Media Limited | Information & communication | 2019 |
| Motion Rides Limited | Arts & recreation | 2010 |
| Motionlogic Limited | Information & communication | 2000 |
| Motionrent Limited | Professional & scientific | 1996 |
| MOTIV8 Properties Ltd | Construction | 2015 |
| MOTIV8SPORTS Ltd | Education | 2024 |
| Motive Music Ltd | Administrative & support | 2011 |
| Motoadventours UK Limited | Administrative & support | 2016 |
| Motor Trade Careers Limited | Administrative & support | 2011 |
| Motorcut Ltd | Information & communication | 2019 |
| Motorplex Limited | Wholesale & retail | 2023 |
| Motorpro Vehicle Solutions Limited | Wholesale & retail | 2023 |
| Mototow Engineers Ltd | Wholesale & retail | 2020 |
| Mottram Construction Ltd | Construction | 2025 |
| Mounfield Consulting Ltd | Professional & scientific | 2017 |
| Mount Decorating and Spraying Ltd | Construction | 2023 |
| Mount Nuclear Safety Ltd | Professional & scientific | 2021 |
| Mount Olympus Bidco Limited | Financial services | 2022 |
| Mount Olympus Midco Limited | Financial services | 2022 |
| Mount Professional Limited | Health & social care | 2025 |
| Mountain Clear Performance Limited | Education | 2017 |
| Mountain Financial Limited | Financial services | 2025 |
| Mountain Road Properties Ltd | Real estate | 2018 |
| Mountaineerin Ltd | Administrative & support | 2014 |
| Mountbatten Capital Partners Ltd | Financial services | 2020 |
| Mountfitchet Sound Ltd | Professional & scientific | 2020 |
| Mountstar Metal Corporation Limited | Extraterritorial | 1968 |
| Mouse Click Systems Ltd | Administrative & support | 2007 |
| Move My Sale Ltd | Other services | 2026 |
| Move Personal Training Ltd. | Administrative & support | 2018 |
| Movica Limited | Professional & scientific | 2017 |
| Moving in Developments Limited | Real estate | 2023 |
| MP Management NW Limited | Professional & scientific | 2026 |
| MP Plan Services Limited | Professional & scientific | 2025 |
| MP Project Management Services Limited | Other services | 2015 |
| MP Rental Properties Limited | Real estate | 2017 |
| MP Travel Group Limited | Transport & logistics | 2019 |
| Mpac Solutions Limited | Administrative & support | 2010 |
| MPB CAD Services Ltd | Professional & scientific | 2019 |
| Mpba Consulting Limited | Information & communication | 2002 |
| Mpba Limited | Information & communication | 2002 |
| MPC Tech Ltd | Information & communication | 2019 |
| MPD Cousins Limited | Information & communication | 2010 |
| MPG Scaffolding Limited | Administrative & support | 2026 |
| MPH Collective Limited | Health & social care | 2025 |
| MPH NW Limited | Real estate | 2019 |
| MPH Services (NW) Limited | Transport & logistics | 2004 |
| MPJ Engineering Ltd | Professional & scientific | 2019 |
| MPJ People Ltd | Administrative & support | 2023 |
| MPJ Retail Consultants Limited | Other services | 2018 |
| Mpkdesigns Ltd | Professional & scientific | 2026 |
| MPO Media Ltd | Information & communication | 2023 |
| Mpower Adhd Ltd | Health & social care | 2022 |
| MPR Property Holdings Limited | Financial services | 2023 |
| MPR Property Lettings Limited | Real estate | 2023 |
| MPS Engineering Ltd | Professional & scientific | 2024 |
| MPS Microbiological Limited | Professional & scientific | 2017 |
| MPS Paving Ltd | Administrative & support | 2025 |
| MPV Technology Limited | Information & communication | 2012 |
| MPW Commercial Services Ltd | Professional & scientific | 2020 |
| MQR Traders Ltd | Wholesale & retail | 2025 |
| MR Blue Shop Ltd | Wholesale & retail | 2024 |
| MR Draughting Limited | Administrative & support | 2011 |
| MR Floors Ltd | Administrative & support | 2018 |
| MR FRY Bolton Limited | Hospitality | 2022 |
| MR Networking & Communications Ltd | Construction | 2020 |
| MR Pink Mini Market Ltd | Wholesale & retail | 2026 |
| Mr.Highline Ltd | Information & communication | 2017 |
| MR3D Ltd | Administrative & support | 2014 |
| MRA Consultancy Ltd | Professional & scientific | 2023 |
| MRA Project Management Limited | Administrative & support | 2016 |
| MRA Restaurant Ltd | Hospitality | 2024 |
| MRB Project Controls Ltd | Professional & scientific | 2023 |
| MRC Consulting Limited | Information & communication | 2024 |
| MRC Site Management Limited | Professional & scientific | 2017 |
| MRE Washed Aggregates Ltd | Water & waste | 2022 |
| MRH Business Solutions Ltd | Administrative & support | 2012 |
| MRH Consultancy Solutions Limited | Construction | 2016 |
| MRH Management Services Limited | Professional & scientific | 2019 |
| MRK2 Limited | Administrative & support | 2013 |
| MRL Commercial Ltd | Professional & scientific | 2024 |
| MRL Compliance Solutions Ltd | Administrative & support | 2025 |
| MRM Accounting Limited | Professional & scientific | 2013 |
| MRP Consulting Limited | Administrative & support | 2023 |
| MRS Monopoly Ltd | Real estate | 2025 |
| Mrtb Consultancy Ltd | Professional & scientific | 2023 |