| Million Years Ltd | Wholesale & retail | 2020 |
| Mills & Mckinney Practice Limited | Health & social care | 2001 |
| Milner Elledge Limited | Professional & scientific | 2018 |
| Miltex Construction Limited | Construction | 2020 |
| Milton Accountants and Consultants Ltd | Professional & scientific | 2017 |
| Milton Education Limited | Professional & scientific | 2012 |
| Milton Ford Properties Limited | Real estate | 2020 |
| Milton Holmfield Ltd | Construction | 2018 |
| Milton House 7 Limited | Real estate | 2025 |
| MIM Pharmacy Limited | Health & social care | 2003 |
| Mims Health Limited | Wholesale & retail | 2021 |
| Minas Ltd | Professional & scientific | 2007 |
| Mindcraft Tech Ltd | Information & communication | 2025 |
| Mindful Health Limited | Health & social care | 2024 |
| Mindmap International Ltd | Wholesale & retail | 2025 |
| Minds and Hearts Ltd | Education | 2023 |
| Mindstream Consulting Ltd | Health & social care | 2025 |
| Mineveal Limited | Real estate | 2025 |
| Minhas Property Holdings Ltd | Real estate | 2026 |
| Mini Digger Services Limited | Construction | 2023 |
| Mini Explorers Outdoor Playgroup Limited | Education | 2022 |
| Mini Milks Children's Boutique Ltd | Wholesale & retail | 2015 |
| Minibusit Ltd | Transport & logistics | 2022 |
| Minsa Enterprise Ltd | Wholesale & retail | 2019 |
| Mint Accounting Solutions Limited | Professional & scientific | 2011 |
| Mint Five Three Ltd | Professional & scientific | 2024 |
| Mintify Limited | Information & communication | 2023 |
| Minuteman Press Romford Ltd | Manufacturing | 2025 |
| Mira Interiors Ltd | Construction | 2013 |
| Mirac Food Ltd | Hospitality | 2025 |
| Miracles Food & Catering Ltd | Hospitality | 2025 |
| Mirada Gallery & Rare Books Ltd | Wholesale & retail | 2025 |
| Miran Security Ltd | Financial services | 2025 |
| Miranda Construction Limited | Construction | 2021 |
| Mirkhan KRD Ltd | Wholesale & retail | 2026 |
| Mirror Translation Ltd | Professional & scientific | 2019 |
| Mirrored Wardrobes Ltd | Wholesale & retail | 2021 |
| Misa Engineering Ltd | Professional & scientific | 2022 |
| Mish Enterprises Ltd | Manufacturing | 2024 |
| Mishkan Ltd | Extraterritorial | 2011 |
| Misi Consultancy Limited | Information & communication | 2018 |
| Miss a Spot Ltd | Administrative & support | 2015 |
| Miss Coipel’S Little Masterminds Limited | Education | 2026 |
| Miss HG Limited | Other services | 2023 |
| Miss Threads Limited | Wholesale & retail | 2023 |
| Miss Threads Wholesale Limited | Wholesale & retail | 2023 |
| Missi Limited | Extraterritorial | 2020 |
| Missiin Ltd | Wholesale & retail | 2020 |
| Missy MOO Franchise Ltd | Wholesale & retail | 2025 |
| Missy MOO Ltd | Wholesale & retail | 2009 |
| Mistcare Limited | Health & social care | 2002 |
| Mistley Residential Limited | Real estate | 2023 |
| Mistri GB Ltd | Construction | 2021 |
| Misu Ltd | Construction | 2019 |
| Mitai Ltd | Hospitality | 2025 |
| Mitchell Maguire Limited | Administrative & support | 2009 |
| Mitchell Maguire Recruitment Limited | Administrative & support | 2023 |
| Mitchell Property Portfolio Ltd | Real estate | 2025 |
| Mitev Transport Services Limited | Transport & logistics | 2018 |
| Mitie FM Group Limited | Administrative & support | 2023 |
| Mitroi Group Limited | Transport & logistics | 2026 |
| Mitu General Services Ltd | Construction | 2015 |
| Miyas Boutique Ltd | Wholesale & retail | 2019 |
| Miyu Limited | Manufacturing | 2026 |
| MIZ Group Services Ltd | Administrative & support | 2024 |
| MJ Coyle Electrical Ltd | Construction | 2010 |
| MJ Mortgages & Protection Ltd | Professional & scientific | 2025 |
| MJ Park Limited | Professional & scientific | 2025 |
| MJA Hire Ltd | Administrative & support | 2024 |
| MJA Technical Services Limited | Construction | 2004 |
| Mjats Holdings Limited | Financial services | 2019 |
| MJB Internationals Ltd | Hospitality | 2018 |
| MJC Environmental Services Limited | Administrative & support | 2012 |
| MJK Property Group Ltd | Real estate | 2025 |
| MJR 12 Limited | Other services | 2017 |
| MJS Healthcare Solutions Limited | Health & social care | 2024 |
| MJU Properties Ltd | Real estate | 2023 |
| MJW Properties Limited | Real estate | 2017 |
| MK & S UK Limited | Professional & scientific | 2011 |
| MK Altron Ltd | Other services | 2018 |
| MK Analysis Ltd | Professional & scientific | 2019 |
| MK Automotive & Sales Ltd | Wholesale & retail | 2026 |
| MK Builders Ltd | Construction | 2022 |
| MK Deluxe Ltd | Construction | 2020 |
| MK Gadgets Ltd | Wholesale & retail | 2026 |
| MK Inspirations Limited | Wholesale & retail | 2025 |
| MK Interim Quality Support Limited | Professional & scientific | 2015 |
| MK Premier Building & Design Ltd | Construction | 2026 |
| MK Project Consultants Ltd | Information & communication | 2019 |
| MK Properties (Essex) Ltd | Real estate | 2020 |
| MK Resources (UK) Ltd | Wholesale & retail | 2021 |
| MK Sales Training Limited | Wholesale & retail | 2015 |
| MK Sonic Vision Ltd | Information & communication | 2026 |
| MKN Property Holdings Ltd | Real estate | 2021 |
| Mkouli Ltd | Wholesale & retail | 2025 |
| MKP Foods London Limited | Hospitality | 2022 |
| MKP IT Research & Development Ltd | Information & communication | 2017 |
| Mkpremium Ltd | Wholesale & retail | 2014 |
| MKS Management Consultants Limited | Wholesale & retail | 2012 |
| ML Counselling Ltd | Health & social care | 2024 |