| Merdex Limited | Professional & scientific | 2018 |
| Merife Health Ltd | Health & social care | 2023 |
| Merli Limited | Other services | 2017 |
| Merryhills Limited | Real estate | 2024 |
| Merton Property Management Limited | Households | 2005 |
| Mesh Events Ltd | Administrative & support | 2023 |
| Messina Transport Limited | Transport & logistics | 2004 |
| Mestijaya Ltd | Hospitality | 2026 |
| Meta Prism Ltd | Wholesale & retail | 2025 |
| Metflam (London) Limited | Financial services | 2012 |
| Metflam Limited | Manufacturing | 2008 |
| Metkowski Ltd | Transport & logistics | 2015 |
| Metroville Properties Limited | Real estate | 2020 |
| Mette Sweets Ltd | Wholesale & retail | 2024 |
| Metwin Limited | Construction | 1958 |
| MEZ Holding Limited | Financial services | 2021 |
| MEZ Safety Ltd | Public administration | 2017 |
| MFB Consulting UK Ltd | Professional & scientific | 2026 |
| Mfmr Consult Limited | Health & social care | 2025 |
| MG White Accountants Ltd | Professional & scientific | 2017 |
| Mg&It Ltd | Information & communication | 2017 |
| Mg-As Construction Ltd | Construction | 2023 |
| MGC Transport Limited | Transport & logistics | 2018 |
| MGD Brickwork & Construction Ltd | Construction | 2025 |
| MGD Properties 5 Ltd | Households | 2021 |
| MGG Locum Health Limited | Health & social care | 2018 |
| Mgmaks Ltd | Transport & logistics | 2019 |
| Mhareece Ltd | Health & social care | 2026 |
| Mhgs Solutions Ltd | Construction | 2026 |
| Mhobus Limited | Administrative & support | 2017 |
| Mhobus Properties Limited | Real estate | 2022 |
| Mhrc Construction Ltd | Construction | 2024 |
| MI Chica Boutique Ltd | Wholesale & retail | 2017 |
| Mia-Ray Studio Ltd | Manufacturing | 2024 |
| Miar Investment Properties Ltd | Real estate | 2024 |
| Mibushu Ltd | Real estate | 2025 |
| Micbrie Medical Services Ltd | Health & social care | 2025 |
| Michael Adekoya World Mission | Other services | 2009 |
| Michael Byrch Limited | Arts & recreation | 2015 |
| Michelle Lauren - Hair Innovation Ltd | Wholesale & retail | 2022 |
| Mick Delivered Ltd | Hospitality | 2022 |
| Microprestige Limited | Wholesale & retail | 2009 |
| MID Night Desserts Limited | Hospitality | 2025 |
| Midas Solutions Limited | Health & social care | 2022 |
| Midaz Ltd | Health & social care | 2023 |
| Midelum Limited | Construction | 2016 |
| Mideol Costedge Consulting Ltd | Construction | 2024 |
| Mihaiella Limited | Transport & logistics | 2025 |
| Mihaloiu Slip Form Ltd | Construction | 2015 |
| Mihu Logistic Ltd | Transport & logistics | 2016 |
| Mihu Trans Limited | Transport & logistics | 2015 |
| Mike Kerr Ltd | Administrative & support | 2006 |
| Mikolajman Ltd | Transport & logistics | 2019 |
| Milano Transport Ltd | Transport & logistics | 2018 |
| Mildmary Service Ltd | Health & social care | 2021 |
| Milestone Road Block F RTM Company Limited | Households | 2025 |
| Milestone RTM Company Limited | Real estate | 2020 |
| Milford ST James Residents Company Limited | Households | 1998 |
| Milizzy Limited | Health & social care | 2022 |
| Mill Quay London E14 (Blocks a, B, F & G) Management Company Limited | Households | 1997 |
| Mill Quay London E14 (Blocks D & E) Management Company Ltd | Households | 1997 |
| Mill Quay London E14 Residents Association Limited | Households | 1996 |
| Millbrook (Harlow) Limited | Real estate | 2024 |
| Millers Landing Management Co. Limited | Households | 1986 |
| Millfields (Southwold) Management Company Limited | Households | 2006 |
| Mills & Co Accountants Ltd | Professional & scientific | 2017 |
| Mills Group Property Limited | Construction | 2025 |
| Mills Group Sprinklers Ltd | Construction | 2026 |
| Milo UK Consulting Ltd | Public administration | 2019 |
| Mimi & Family Ltd | Manufacturing | 2025 |
| MIN Construction Ltd | Construction | 2022 |
| Minal's Kitchen Enfield Ltd | Hospitality | 2025 |
| Mincarlo Media Limited | Information & communication | 2022 |
| Mind in West Essex | Health & social care | 2002 |
| Mindedgrowth Ltd | Information & communication | 2021 |
| Mindhelpa Ltd | Information & communication | 2025 |
| Mindjammer Press Limited | Arts & recreation | 2012 |
| Mindmend Solutions Ltd | Health & social care | 2024 |
| Minfab Services Limited | Health & social care | 2019 |
| Mingoia Properties Limited | Real estate | 2016 |
| Mini Delikatesy Kubus Ltd | Wholesale & retail | 2009 |
| Mini Parcels Logistics Ltd | Transport & logistics | 2021 |
| Mini Shooters Ltd | Education | 2023 |
| Ministry of Liberation Limited | Administrative & support | 2016 |
| Minkah Consulting Limited | Professional & scientific | 2025 |
| Minnies House Ltd | Wholesale & retail | 2025 |
| Minra Windows and Doors Ltd | Extraterritorial | 2023 |
| Minstrel Stag Ltd | Real estate | 2024 |
| MIR Mart Ltd | Wholesale & retail | 2025 |
| Mira Mira Tanning and Beauty Limited | Other services | 2013 |
| Mira Nails Limited | Other services | 2024 |
| Miracle K Events Ltd | Administrative & support | 2025 |
| Mirakel Consortium Community Interest Company | Hospitality | 2022 |
| Mirakle Healthcare International Ltd | Health & social care | 2014 |
| Miras Family Estates Ltd | Real estate | 2021 |
| Miraur Ltd | Health & social care | 2016 |
| Mirdav Ltd | Transport & logistics | 2025 |
| Mirelstar Limited | Transport & logistics | 2025 |
| Mirox Accountancy Ltd | Professional & scientific | 2016 |
| Miroxnich Clothing Ltd | Wholesale & retail | 2020 |