| MJS Investment Group Ltd | Wholesale & retail | 2017 |
| MK Car Breakers Ltd | Water & waste | 2024 |
| MK Fire & Electrical Services Limited | Construction | 2022 |
| MK Mobile & Vapes Ltd | Wholesale & retail | 2026 |
| MK QA Management Consultants Limited | Professional & scientific | 2024 |
| MK Surgeries Ltd | Real estate | 2021 |
| MK Visionary Ltd | Transport & logistics | 2025 |
| Mkas Properties Limited | Real estate | 2015 |
| Mkkdp Ltd | Real estate | 2026 |
| MKV Construction Services Limited | Construction | 2022 |
| Mkveansons Limited | Construction | 2015 |
| Mkvs & Sons Ltd | Wholesale & retail | 2025 |
| MKW Medical Limited | Health & social care | 2015 |
| MLA Louis Limited | Extraterritorial | 2019 |
| Mlash Ltd | Other services | 2024 |
| Mlcc Limited | Construction | 2018 |
| MLL Point Ltd | Administrative & support | 2023 |
| Mlrcom Ltd | Wholesale & retail | 2016 |
| Mlsd Group Ltd | Professional & scientific | 2022 |
| Mlsm Consulting Limited | Professional & scientific | 2013 |
| MM Fitness Ltd | Health & social care | 2015 |
| MM Heating & Bathrooms Ltd | Construction | 2023 |
| MM Maintenance Services Ltd | Construction | 2025 |
| MM Miholca Ltd | Construction | 2019 |
| MM Partners One Ltd | Wholesale & retail | 2020 |
| Mm&H Construction Ltd | Construction | 2026 |
| MMZ Investments Limited | Extraterritorial | 2021 |
| MND Autos Ltd | Wholesale & retail | 2010 |
| Mndm Limited | Professional & scientific | 2024 |
| MO & MO Services Ltd | Information & communication | 2021 |
| Mo:Studio Ltd | Information & communication | 2003 |
| Moana Investments Limited | Real estate | 2021 |
| Moayedirealestate Limited | Real estate | 2024 |
| Mobile Atlus Ltd | Wholesale & retail | 2014 |
| Mobile Car Services (London) Ltd | Manufacturing | 2013 |
| Mobility Services Limited | Professional & scientific | 2019 |
| Mobsalon Ltd | Other services | 2025 |
| Mocassin Limited | Extraterritorial | 2021 |
| Mochamore Limited | Professional & scientific | 2015 |
| Moddex Limited | Other services | 1974 |
| Modern General Building Ltd | Construction | 2020 |
| Modern Skylights Ltd | Manufacturing | 2019 |
| Modesara Estates Limited | Financial services | 2026 |
| MODH07 Limited | Wholesale & retail | 2026 |
| Modish Ware Ltd | Wholesale & retail | 2023 |
| Modo Management Limited | Real estate | 2019 |
| Modrez Limited | Other services | 2016 |
| Moffat Camberwell Limited | Real estate | 2025 |
| Moffat Folkestone Ltd | Real estate | 2023 |
| Moffat Granville Gardens Limited | Real estate | 2024 |
| Moffat Investments Ltd | Real estate | 2014 |
| Mohabat Afghan Food Ltd | Hospitality | 2024 |
| Mohinika Beverages Limited | Other services | 2009 |
| Mohri Ltd | Transport & logistics | 2020 |
| Mohthus Ltd | Wholesale & retail | 2024 |
| Moide Essentials Limited | Hospitality | 2022 |
| MOJ E ABI Ltd | Financial services | 2025 |
| Mojja Groceries Limited | Hospitality | 2022 |
| MOK Construction Ltd | Construction | 2016 |
| Moky Consulting Limited | Professional & scientific | 2014 |
| Mollison Cash & Carry Limited | Wholesale & retail | 2012 |
| Mollison Properties Ltd | Real estate | 2017 |
| Molly Munch Management Limited | Real estate | 2017 |
| Mollys Car Breakers Ltd | Wholesale & retail | 2026 |
| Momentum Movement CIC | Health & social care | 2026 |
| Momentum Residential Care Home Ltd | Health & social care | 2018 |
| Momo Eliquid Limited | Manufacturing | 2016 |
| Momo Kitchen Ltd | Hospitality | 2024 |
| Moms&Sons Care Limited | Health & social care | 2025 |
| MON Amour Ltd | Wholesale & retail | 2023 |
| Mond 458 Ltd | Real estate | 2020 |
| Mondial Interiors Ltd | Construction | 2026 |
| Monetise Trust Ltd | Financial services | 2025 |
| Moni Care Service Limited | Health & social care | 2024 |
| Monkey Empire Limited | Real estate | 2014 |
| Monks Way Development Limited | Construction | 2015 |
| Monkville Avenue Ltd | Real estate | 2022 |
| Monotaha Limited | Administrative & support | 2011 |
| Montagu Baker Ltd | Real estate | 2012 |
| Montague Ltd | Real estate | 2018 |
| Montague Mews Limited | Households | 2023 |
| Montague Parsons Investments Limited | Real estate | 2015 |
| Montague Parsons Limited | Professional & scientific | 2015 |
| Montefiore Bridging Finance Ltd | Financial services | 2011 |
| Montesque Limited | Professional & scientific | 2024 |
| Montpelier NW11 Ltd | Real estate | 2022 |
| Montrovian Investments Limited | Real estate | 2013 |
| Montruseai Tech Ltd | Professional & scientific | 2025 |
| Montworth Limited | Real estate | 1963 |
| Monza International Ltd | Wholesale & retail | 2023 |
| Moochoh Limited | Hospitality | 2022 |
| Moon Academy CIC | Other services | 2015 |
| Moon River Media Limited | Information & communication | 2007 |
| Moonia Falkirk Ltd | Other services | 2025 |
| Moontiti Limited | Professional & scientific | 2026 |
| Moor Lane Laundry Limited | Other services | 2022 |
| Moor Properties & Finance Limited | Professional & scientific | 1982 |
| Moore & Sons Heating and Plumbing Limited | Construction | 2021 |
| Moores A&A Ltd | Wholesale & retail | 2026 |
| Moose Property Inventories Limited | Real estate | 2024 |