| Message From the Ravens Ltd | Information & communication | 2022 |
| Metamorph Strategic Consulting Ltd | Transport & logistics | 2017 |
| Meyrem Restaurant Ltd | Hospitality | 2018 |
| MGA Property Consultancy Ltd | Households | 2025 |
| MGM Brickwork Contractors Ltd | Construction | 2008 |
| MGR Developments Ltd | Construction | 2020 |
| MGR Progressions Ltd | Construction | 2019 |
| MH Legal Consulting Limited | Professional & scientific | 2015 |
| Mhairi Textiles Ltd | Manufacturing | 2020 |
| Mhhm Group Ltd | Agriculture & fishing | 2025 |
| MI Home Ltd | Households | 2020 |
| Michael Tyler Furniture (UK) Limited | Manufacturing | 2007 |
| Michelle Gilson Ltd | Professional & scientific | 2022 |
| Middle Middle Ltd | Transport & logistics | 2018 |
| Middle Years Monday Limited | Health & social care | 2019 |
| Miikiin Ltd | Hospitality | 2022 |
| Millco Ltd | Professional & scientific | 2019 |
| Miller and Stone Limited | Construction | 2021 |
| Milo Nguyen Limited | Other services | 2022 |
| Minc Limited | Professional & scientific | 2014 |
| Mind Matters Psychology Ltd | Health & social care | 2016 |
| Mindset Marketing Limited | Professional & scientific | 2024 |
| Minerva Archaeology Limited | Professional & scientific | 2019 |
| Mitis Health Ltd | Information & communication | 2020 |
| Mitten & Leigh Ltd | Construction | 2022 |
| MJB 1066 Limited | Construction | 2023 |
| MJG Repairs and Maintenance Limited | Other services | 2016 |
| Mjt&G Contracting Limited | Professional & scientific | 2025 |
| MLC Funerals Ltd | Other services | 2023 |
| Moda Leisure Limited | Hospitality | 2006 |
| Mode 001 Ltd | Real estate | 2023 |
| Modulith Ltd | Information & communication | 2026 |
| Modulith Research CIC | Professional & scientific | 2026 |
| Money Investments Limited | Real estate | 2013 |
| Monolith Investments Ltd | Real estate | 2025 |
| Montsechia Vidalii CIC | Wholesale & retail | 2025 |
| Mooboo Hastings Limited | Hospitality | 2021 |
| Moonbear Media Ltd | Information & communication | 2024 |
| Moonlight Bidco Limited | Financial services | 2023 |
| Moonlight Midco 1 Limited | Financial services | 2023 |
| Moonlight Midco 2 Limited | Financial services | 2023 |
| Moonlight Topco Limited | Financial services | 2023 |
| Moorcroft House 212A Battle ST ST Leonards Limited | Households | 2009 |
| More Fountains Ltd | Arts & recreation | 2025 |
| More Kicks UK Ltd | Wholesale & retail | 2020 |
| Moreton Court Residents Association Limited | Households | 2002 |
| Morleys Construction Limited | Construction | 2022 |
| Morris Accounting Ltd | Professional & scientific | 2020 |
| Mota Services Limited | Wholesale & retail | 2010 |
| Motogusto Limited | Information & communication | 2020 |
| Mount Pleasant Barbers Ltd | Other services | 2020 |
| Mountmellick Music Ltd. | Information & communication | 2015 |
| MP Aviation and Displays Ltd | Other services | 2016 |
| MPT Holdings Limited | Financial services | 2020 |
| MR & MRS P Hanlon Portfolio a Limited | Real estate | 2018 |
| MR & MRS P Hanlon Portfolio B Limited | Real estate | 2018 |
| MR & MRS P Hanlon Portfolio C Limited | Real estate | 2022 |
| MR & MRS P Hanlon Portfolio D Limited | Real estate | 2022 |
| MR and MRS P Hanlon Group Limited | Financial services | 2016 |
| MR Powers Electrical Ltd | Construction | 2016 |
| MSL Discover | Arts & recreation | 2018 |
| MTD for Itsa Ltd | Extraterritorial | 2025 |
| Mtll Estates Limited | Real estate | 2026 |
| Mulvaney Project Management Ltd | Construction | 2025 |
| Mulvaney Surveying Limited | Professional & scientific | 2015 |
| Mummy Food Limited | Hospitality | 2018 |
| Munchbox 1066 Limited | Hospitality | 2020 |
| Murray & Bigg Decorating Limited | Construction | 2020 |
| My Future Starts Here (East Sussex) Ltd | Education | 2024 |
| Mybikestation Limited | Professional & scientific | 2010 |
| Myson Flat Management Limited | Households | 1999 |
| Mytogen Limited | Professional & scientific | 2011 |
| Mühle UK Ltd | Wholesale & retail | 2018 |
| N B Building Services (South East) Ltd | Construction | 2017 |
| Nanospin Ltd | Manufacturing | 2023 |
| Narniapub Ltd | Hospitality | 2019 |
| Nautical Museums Trust Limited | Arts & recreation | 1982 |
| NAZ Constructions Limited | Construction | 2025 |
| Near Lots (Peninsula) Limited | Construction | 2025 |
| Near Lots (Plot H) Limited | Real estate | 2025 |
| Neat and Shiny Limited | Administrative & support | 2023 |
| Nectar Real Estates & Investments Ltd | Real estate | 2025 |
| Needs Must Ltd | Extraterritorial | 2019 |
| Neil Sharp Ltd | Arts & recreation | 2013 |
| Neon Brenda Limited | Information & communication | 2022 |
| Netshare Computers LLP | | 2007 |
| Netshare Limited | Information & communication | 1998 |
| Nevelle Property Solutions Ltd | Real estate | 2019 |
| New England Homes Limited | Real estate | 1935 |
| New Life Properties Limited | Hospitality | 2003 |
| New Powermend Limited | Manufacturing | 2026 |
| New Street Studios Ltd | Construction | 2007 |
| NEWCHAPTER@T2T4C Limited | Education | 2017 |
| Newmarc Commercial Ltd | Construction | 2025 |
| Next Door Property LLP | | 2006 |
| Next Model Media Limited | Information & communication | 2023 |
| Nextgen National Ltd | Construction | 2025 |
| Nexus (East Sussex) Limited | Construction | 2022 |
| Nexus (South East) Limited | Construction | 2020 |
| Nexus Joinery (South East) Limited | Manufacturing | 2025 |