| MHK (SE) Limited | Administrative & support | 2024 |
| Michael Sayeau Ltd | Education | 2019 |
| Michelle Louise Residential Ltd | Real estate | 2026 |
| Microrose International Limited | Professional & scientific | 2004 |
| Midgard Advisors Limited | Information & communication | 2023 |
| Midlife Space Limited | Information & communication | 2021 |
| Midnight OIL Productions (Theatre) Limited | Arts & recreation | 2026 |
| Mighty Mole Limited | Wholesale & retail | 2021 |
| Miles Social Care Associates Ltd | Health & social care | 2022 |
| Miller Brickwork Ltd | Construction | 2020 |
| Miller Connections Limited | Information & communication | 2020 |
| Miller's Building & Maintenance Services Limited | Transport & logistics | 2017 |
| Millers Building Kent Limited | Construction | 2025 |
| Millers ROW (Management Company) Limited | Households | 2015 |
| Millwater Property Limited | Information & communication | 2009 |
| MIM Stays Limited | Real estate | 2026 |
| Minters Holdings Limited | Financial services | 2013 |
| Mitsinga Film Services Ltd | Transport & logistics | 2025 |
| MJA Consulting Engineers Ltd | Professional & scientific | 2014 |
| MJA Estates Management Ltd | Real estate | 2021 |
| MJK Properties (South East) LLP | | 2012 |
| MJM Consulting Limited | Information & communication | 1998 |
| MJS Heating Ltd | Construction | 2026 |
| MK Leavey Floor Screeding Limited | Construction | 2020 |
| MKG Maintenance Ltd | Administrative & support | 2021 |
| MMP Financial Planning Limited | Financial services | 2013 |
| MMP Limited | Professional & scientific | 2003 |
| MNJ Electrics Limited | Construction | 2022 |
| Moare Solutions Ltd | Health & social care | 2020 |
| Moasic Ltd | Construction | 2019 |
| Mobile Auto Repair Kent Ltd | Professional & scientific | 2026 |
| Momentum Management Consultancy Ltd | Professional & scientific | 2025 |
| Moneyful Ltd | Arts & recreation | 2021 |
| Monica Martinez Ltd | Professional & scientific | 2023 |
| Monk & Toogood Limited | Manufacturing | 2008 |
| Montravia Limited | Wholesale & retail | 1977 |
| Moorhouse Medical Limited | Health & social care | 2020 |
| Moorlands Court Management Company (Dewsbury) Limited | Households | 2006 |
| Morgan Bridgland Partners Ltd | Professional & scientific | 2025 |
| Morgan's Pomade Company Limited | Manufacturing | 1938 |
| Mosaic (Whitstable) Ltd | Wholesale & retail | 2013 |
| Mossy's Motors Limited | Wholesale & retail | 2024 |
| Moth TLC Ltd | Health & social care | 2024 |
| Mother Property Ltd | Wholesale & retail | 2011 |
| Mother PUP Limited | Manufacturing | 2020 |
| MOTIV8 Property Solutions Ltd | Real estate | 2019 |
| Mould Management Ltd | Administrative & support | 2023 |
| Mounts Removals & Storage Limited | Transport & logistics | 2018 |
| Move on UP Coaching Ltd | Other services | 2024 |
| Movement for Health Limited | Health & social care | 2021 |
| Moving Communities Forward 2016 Ltd | Other services | 2016 |
| MPH Accountancy & Business Advisors Ltd | Administrative & support | 2019 |
| Mphpm Ltd | Construction | 2024 |
| MPN Process Solutions Limited | Administrative & support | 2013 |
| Mrdncorp Ltd | Wholesale & retail | 2025 |
| MRL Management Company Limited | Extraterritorial | 2010 |
| MSA First AID Training Ltd | Education | 2025 |
| MSW Transport & Asphalt Ltd | Transport & logistics | 2023 |
| Mtarch Ltd | Professional & scientific | 2021 |
| MTL Wholesale Ltd | Wholesale & retail | 2023 |
| Mulini & Mulini Ltd | Construction | 2023 |
| Mullingar Homes Limited | Real estate | 2017 |
| Murphy Builders (Kent) Limited | Construction | 2003 |
| Murray Parris Lettings Limited | Administrative & support | 2014 |
| Musa Collective Limited | Construction | 2021 |
| Mustard Rigging Ltd | Other services | 2012 |
| Mutica Limited | Real estate | 2011 |
| MV4U Ltd | Wholesale & retail | 2021 |
| MW Legacy Group Ltd | Financial services | 2026 |
| My Estate Holdings Ltd | Financial services | 2022 |
| My Harbour Street LLP | | 2023 |
| My High Street Ltd | Real estate | 2022 |
| My Holiday Homes Ltd | Real estate | 2023 |
| My Landlady Properties Limited | Real estate | 2018 |
| My Plumbing & Heating Ltd | Construction | 2009 |
| My Property Needs A.Com Ltd | Information & communication | 2017 |
| My Renewables Ltd | Professional & scientific | 2024 |
| My Salon Whitstable Ltd | Other services | 2025 |
| MYO Limited | Extraterritorial | 2025 |
| Mysd Holdco Ltd | Financial services | 2026 |
| Mysd Investco Ltd | Extraterritorial | 2026 |
| Mysd Management Ltd | Other services | 2023 |
| Mystic Fate Limited | Wholesale & retail | 2023 |
| N DEW Ltd | Wholesale & retail | 2016 |
| N R Hardy Ltd | Administrative & support | 2024 |
| N W Ventilation Limited | Administrative & support | 2009 |
| Nackington Court Estate Limited | Households | 1962 |
| Narina Ltd | Manufacturing | 2013 |
| Nash Court Developments Limited | Real estate | 2019 |
| National Nines Golf Ltd | Administrative & support | 2025 |
| Naughton Safety Limited | Construction | 2025 |
| Nautilus Property Management Ltd | Households | 2024 |
| Nbrhd Ltd | Professional & scientific | 2026 |
| Nctrnl Events Ltd | Arts & recreation | 2019 |
| NDR Builders Limited | Construction | 1999 |
| Neighbourhood Wash Window Cleaning Limited | Administrative & support | 2023 |
| Nellary Fuels Limited | Wholesale & retail | 2019 |
| Nellary UK Ltd | Wholesale & retail | 2015 |
| Netstars Netball Ltd | Arts & recreation | 2013 |
| Newby Design Engineering Limited | Professional & scientific | 2021 |