| Metric Scaffold (S.E) Limited | Construction | 2004 |
| Metro Fleet Engineering Ltd | Wholesale & retail | 2026 |
| Metrop UK Limited | Wholesale & retail | 2021 |
| Mezzanine Guru Ltd | Construction | 2023 |
| MF Investments Limited | Construction | 2024 |
| MFA Properties Limited | Real estate | 2009 |
| MG Refrigeration Services Limited | Manufacturing | 2000 |
| MG Where Your Story Matters Limited | Information & communication | 2023 |
| MG Your Story Matters Limited | Information & communication | 2023 |
| MGM Finance Ltd | Real estate | 2015 |
| MH Bodyworx Ltd | Wholesale & retail | 2016 |
| MHJ Building Services Ltd | Construction | 2024 |
| Mhouse Group Limited | Real estate | 2022 |
| Mibos Building Ltd | Transport & logistics | 2014 |
| Micbam NIG UK Ltd | Information & communication | 2016 |
| Micemma Ltd | Public administration | 2023 |
| Michael Milano Photography Ltd | Professional & scientific | 2026 |
| Michael Parkes Surveyors Limited | Real estate | 1987 |
| Mick's Mot's Service & Repairs Limited | Wholesale & retail | 2016 |
| Mickiwa Limited | Professional & scientific | 2025 |
| Micks Construction Limited | Construction | 2021 |
| Mick’S Mot’S Testing Limited | Wholesale & retail | 2016 |
| Mid-Kent Van Centre Ltd | Wholesale & retail | 2020 |
| Midda DKK Properties Ltd | Real estate | 2015 |
| Middleton Residents Limited | Real estate | 1986 |
| Midland Steel Reinforcement Supplies (GB) Limited | Manufacturing | 2010 |
| Midnight House Ltd | Arts & recreation | 2026 |
| Midolex Transport Ltd | Transport & logistics | 2025 |
| Might Property Limited | Households | 2022 |
| Migrants Square CIC | Administrative & support | 2024 |
| Miguel Records Ltd | Arts & recreation | 2026 |
| Mika Motivation Ltd | Other services | 2021 |
| Mike Reed Promotions Ltd | Administrative & support | 2008 |
| Mikelazenby.Com Ltd | Professional & scientific | 1999 |
| Mikeomot Ltd | Construction | 2019 |
| Mikes Maindrain Ltd | Water & waste | 2014 |
| Miki&S Company Ltd | Construction | 2019 |
| Milano Barbers Kent Ltd | Other services | 2025 |
| Miljen Bathrooms Limited | Construction | 2018 |
| Mill & Rise Limited | Wholesale & retail | 2026 |
| Mill Works Management Limited | Households | 2008 |
| Millam Limited | Professional & scientific | 1998 |
| Millennial Homes Limited | Administrative & support | 2018 |
| Mills Osborn Partnership Ltd | Financial services | 2008 |
| Milton Court (Gravesend) Residents Association Limited | Households | 1985 |
| Milton Electrical Engineers Limited | Construction | 1995 |
| Milton House (at 62A High Street Milton Regis ME10 2AN) Limited | Hospitality | 2017 |
| Mindn Ltd | Wholesale & retail | 2018 |
| Minds EYE Ltd | Extraterritorial | 2020 |
| Mindspark Edge Ltd | Education | 2025 |
| Mini Gabi Ltd | Administrative & support | 2017 |
| Minion Tickets Ltd | Wholesale & retail | 2025 |
| Minor Key Pottery Limited | Manufacturing | 2020 |
| Mint Vault UK Ltd | Administrative & support | 2026 |
| Mints FX Ltd | Other services | 2022 |
| Mints Group Ltd | Information & communication | 2018 |
| Mira Threads Ltd | Wholesale & retail | 2025 |
| Miranda Double Glazing (EOT) Limited | Financial services | 2024 |
| Miranda Double Glazing Limited | Construction | 2003 |
| Miris.Sh Ltd | Wholesale & retail | 2024 |
| Mirovittd Ltd | Construction | 2020 |
| Mirror Mirror Beauty & Aesthetics Ltd | Other services | 2021 |
| Miso Consults Ltd | Real estate | 2025 |
| Miss Gloria Limited | Arts & recreation | 2017 |
| Mission Baits UK Ltd | Manufacturing | 2016 |
| Mistek Electrical Limited | Construction | 2025 |
| Mistek Limited | Public administration | 2016 |
| Mister Sparkle Limited | Administrative & support | 2003 |
| MIT Business Hub Ltd | Manufacturing | 1989 |
| MIT Design Hub Ltd | Manufacturing | 1989 |
| MIT Hub Ltd | Professional & scientific | 1989 |
| MIT Software Hub Ltd | Professional & scientific | 1998 |
| Mitchell Investors Group Ltd | Real estate | 2025 |
| Miyah Ltd | Administrative & support | 2019 |
| MJ Oaks Ltd | Professional & scientific | 2021 |
| MJ Tyres Ltd | Manufacturing | 2020 |
| Mjaut Limited | Transport & logistics | 2024 |
| MJB Project Solutions Ltd | Construction | 2025 |
| MJB Utilities Ltd | Construction | 2023 |
| MJE Consultancy Services Ltd | Professional & scientific | 2026 |
| MJK Access Ltd | Construction | 2021 |
| MJS300 Properties Limited | Real estate | 2023 |
| MK Care Provision Ltd | Health & social care | 2020 |
| MK Property Maintenance Limited | Construction | 2019 |
| MK Spark Ltd | Wholesale & retail | 2015 |
| MK Sparkles Ltd | Administrative & support | 2026 |
| Mkundu Ltd | Real estate | 2020 |
| Mlml Property Limited | Real estate | 2024 |
| Mlzl Limited | Real estate | 2019 |
| MM Motoring Group Limited | Administrative & support | 2026 |
| MME Estates Limited | Real estate | 2025 |
| Mmrs Consulting Limited | Information & communication | 2021 |
| MND Installations Limited | Construction | 2019 |
| MNE Building Services Ltd | Construction | 2019 |
| MNM Rose Limited | Real estate | 2023 |
| MNS Kent Carpentry Ltd | Manufacturing | 2021 |
| Mockbeggar Developments Limited | Construction | 2004 |
| Mockbeggar Packing Limited | Administrative & support | 2009 |
| Mockbeggar PO Limited | Other services | 2024 |
| Modereal Limited | Professional & scientific | 1989 |