| Millenia Bay Ltd | Administrative & support | 2025 |
| Millennium Hair & Beauty Ltd | Wholesale & retail | 2024 |
| Millipore (U.K.) Limited | Professional & scientific | 2000 |
| Milonga Consulting Ltd | Professional & scientific | 2011 |
| Minaro Ltd | Construction | 2019 |
| Minataur Ltd | Wholesale & retail | 2022 |
| Mindbrew Limited | Information & communication | 2023 |
| Mindful Manifestation Ltd | Other services | 2024 |
| Minicabco Ltd | Transport & logistics | 2013 |
| Minotaur Clothing Ltd | Manufacturing | 2012 |
| Minxtown Limited | Other services | 2016 |
| MIR & Sons Solicitors Ltd | Professional & scientific | 2010 |
| Mirakulous Gaming Ltd | Wholesale & retail | 2025 |
| Miratoni Ltd | Wholesale & retail | 2010 |
| Misheetha Consulting Limited | Information & communication | 2013 |
| Missyeti Limited | Wholesale & retail | 2022 |
| Mistry Gems Ltd | Wholesale & retail | 2017 |
| Mixed Freight Holdings Limited | Financial services | 2013 |
| Mixed Freight Services Limited | Transport & logistics | 1985 |
| Mixt Academy Ltd | Education | 2025 |
| Mixtrans Ltd Ltd | Transport & logistics | 2024 |
| Miyabi Services Ltd | Other services | 2021 |
| MIZPEHJ723 Limited | Real estate | 2019 |
| MJ Dealers Limited | Wholesale & retail | 2025 |
| MJ Dreams Company Limited | Construction | 2023 |
| MJ. Haral Ltd | Wholesale & retail | 2024 |
| MJJ Flooring Ltd | Construction | 2020 |
| MJP Global Ltd | Health & social care | 2015 |
| MK Cleaning Company Ltd | Administrative & support | 2024 |
| MK Guardian K9 & Facilities Ltd | Administrative & support | 2026 |
| MK Motors London Limited | Wholesale & retail | 2026 |
| MKE Residential Renovations Ltd | Construction | 2021 |
| MKM Properties Limited | Real estate | 2025 |
| MKR Homes Ltd | Real estate | 2026 |
| ML Electrical Ltd | Construction | 2019 |
| Mlode Limited | Information & communication | 2003 |
| MM90 Services Ltd | Construction | 2025 |
| MMN General Trading Ltd | Construction | 2014 |
| MNG Services COL3:17 Ltd | Administrative & support | 2021 |
| MNJ Logistics Ltd | Transport & logistics | 2024 |
| MNM Bargains Ltd | Wholesale & retail | 2025 |
| MNR Estates Limited | Real estate | 2022 |
| Mnuk Ltd | Information & communication | 2025 |
| Mo-Ver 23 Limited | Construction | 2023 |
| Mobile Cargo Security Limited | Other services | 2017 |
| Moda 2 Style Ltd | Wholesale & retail | 2014 |
| Moda CUT 5 Ltd | Other services | 2025 |
| Modelkut Fitness Ltd | Arts & recreation | 2025 |
| Modern Lifestyle Properties Ltd | Real estate | 2021 |
| Modi Accountants Limited | Professional & scientific | 2022 |
| Modish International Ltd | Wholesale & retail | 2024 |
| Moisturefix Ltd | Construction | 2026 |
| Mokriq Ltd | Wholesale & retail | 2024 |
| Momo & Messing Limited | Hospitality | 2025 |
| MON Abri Care Ltd | Health & social care | 2024 |
| Money Matters Accountancy Ltd | Professional & scientific | 2024 |
| Monkey Consulting Limited | Information & communication | 2012 |
| Monoo London Ltd | Manufacturing | 2019 |
| Monopify Ltd | Information & communication | 2025 |
| Monster BID Limited | Wholesale & retail | 2014 |
| Monster Cleaning Ltd | Administrative & support | 2015 |
| Montoya Marketing Limited | Information & communication | 2023 |
| Monument Ltd | Construction | 2024 |
| Moonlight Food Ltd | Hospitality | 2022 |
| Moonlit Beauty Ltd | Other services | 2020 |
| More Than Doors Limited | Construction | 2009 |
| More Then Doors Ltd | Construction | 2023 |
| MORET1 Transport Ltd | Manufacturing | 2019 |
| Morphix Learning Hub Ltd | Administrative & support | 2017 |
| Mortello 66 Ltd | Real estate | 2021 |
| Morville Street Assets Limited | Real estate | 2017 |
| Mosch International Ltd | Wholesale & retail | 2024 |
| Mossy Ltd | Wholesale & retail | 2015 |
| Motorbike Clinic Ltd | Wholesale & retail | 2017 |
| Motoring School Ltd | Education | 2021 |
| Motorspoint Ltd | Wholesale & retail | 2023 |
| Motortec Limited | Wholesale & retail | 2008 |
| Move Clean & Clear Ltd | Transport & logistics | 2026 |
| Move Mates Limited | Real estate | 2024 |
| Movie Craft Limited | Information & communication | 1997 |
| Movivan Ealing Ltd | Transport & logistics | 2024 |
| Movivan Heathrow Limited | Transport & logistics | 2019 |
| Movivan Ltd | Transport & logistics | 2015 |
| Movsesov Limited | Transport & logistics | 2013 |
| Moxom Heating Ltd | Construction | 2020 |
| MQ Construction Ltd | Construction | 2024 |
| MQ Pharm Ltd | Agriculture & fishing | 2022 |
| MR Gurpreet Singh Ltd | Wholesale & retail | 2025 |
| MR Marcelos Limited | Transport & logistics | 2023 |
| MR Sidhu Ltd | Real estate | 2021 |
| Mrhd Investments Ltd | Real estate | 2025 |
| Mrhd Limited | Transport & logistics | 2019 |
| MS Global Softtech Ltd | Information & communication | 2010 |
| MSA Scaffolding Ltd | Construction | 2016 |
| Msgautos Ltd | Professional & scientific | 2025 |
| MSK & RZI Ltd | Households | 2025 |
| MSL Cabling Limited | Construction | 2019 |
| MSL Labour Ltd | Administrative & support | 2022 |
| MSL MEP Solutions Ltd | Administrative & support | 2024 |
| MSR Screeding Ltd | Construction | 2021 |