| Longevity Fitness Ltd | Arts & recreation | 2026 |
| Lost Local Ltd | Wholesale & retail | 2023 |
| Louise Collinson Equine Rehabilitation Ltd | Agriculture & fishing | 2020 |
| Loxton Estate Ltd | Agriculture & fishing | 2022 |
| Loyalty Healthcare Solutions Limited | Health & social care | 2017 |
| LTK Consultancy Ltd | Professional & scientific | 2025 |
| Lucian Trandafir Limited | Extraterritorial | 2019 |
| Lugo Enterprises Ltd | Hospitality | 2018 |
| Luke Jenkins Building Surveyors Ltd | Professional & scientific | 2018 |
| Lummlec Ltd | Construction | 2021 |
| Luxury Nails 61C Ltd | Other services | 2022 |
| Luxury Polishing Limited | Other services | 2023 |
| Luxury Timepiece Vault Ltd | Wholesale & retail | 2025 |
| Luxyspace Ltd | Administrative & support | 2025 |
| LVH Contracting Limited | Construction | 2015 |
| Lyfthaus Limited | Manufacturing | 1995 |
| M Mcgrady Ltd | Professional & scientific | 2024 |
| M Turton Brickwork Limited | Construction | 2007 |
| M&M Vapes Ltd | Wholesale & retail | 2025 |
| M. Cunnington Upholstery Centre Limited | Other services | 1998 |
| M.T.S. Install Ltd | Administrative & support | 2015 |
| Maara Homes Ltd | Real estate | 2024 |
| Maargin Research and Innovation Limited | Information & communication | 2025 |
| Mach Abseiling Ltd | Construction | 2020 |
| Machinepart Engineering Limited | Manufacturing | 1999 |
| Madeira Cafe Ltd | Hospitality | 2021 |
| Magic Scissors Haverhill Ltd | Other services | 2018 |
| Magic Touch (Haverhill) Limited | Other services | 2007 |
| Magic Wand Property Cleaning Company Limited | Administrative & support | 2012 |
| Magical Moments by Anna Ltd | Professional & scientific | 2024 |
| Magna Radiator Ltd | Manufacturing | 2025 |
| Manfred Solutions Ltd | Manufacturing | 2025 |
| Mannings Farm Events Ltd | Real estate | 2024 |
| Mansol (Preforms) Limited | Manufacturing | 1954 |
| Mansol Holdings Limited | Professional & scientific | 2002 |
| Manujah Trading Ltd | Wholesale & retail | 2021 |
| Maraly Ltd | Transport & logistics | 2018 |
| Marbles of Delaware Limited | Wholesale & retail | 2016 |
| Mark Wilsher Design & Build Ltd | Construction | 2013 |
| Market Data Services International Limited | Information & communication | 2025 |
| Marriage Settlement Renewables Limited | Administrative & support | 2013 |
| Marshall Davis Limited | Construction | 2018 |
| Mary Fenner Chiropodist Ltd | Health & social care | 2005 |
| Mary Healthcare Solutions Limited | Health & social care | 2018 |
| Marylands Consulting Limited | Administrative & support | 2010 |
| Mason Greenfields Limited | Financial services | 2010 |
| Matkey Ltd | Health & social care | 2011 |
| Matrix Cellular International Services UK Limited | Information & communication | 1999 |
| Matt-Pack Ltd | Wholesale & retail | 2013 |
| Mattcare and Secure Limited | Other services | 2018 |
| Maverick Approach Ltd | Wholesale & retail | 2024 |
| Mavnewstreet Ltd | Real estate | 2026 |
| Mavv Trans Limited | Transport & logistics | 2021 |
| Maximum Animal Health Ltd | Wholesale & retail | 2002 |
| MAZ 96 Ltd | Hospitality | 2019 |
| MBM Structures Ltd | Construction | 2015 |
| Mcbrien Carpentry Ltd | Construction | 2013 |
| Mccue Consultancy Services Ltd | Information & communication | 2023 |
| Mcgrath Developments Ltd | Financial services | 2023 |
| Mclearlong Property Solutions Ltd | Real estate | 2025 |
| Mcleod Cabins Limited | Construction | 1992 |
| MCP MMC Limited | Wholesale & retail | 2017 |
| MCS Investments Limited | Real estate | 1997 |
| MCT Contracts Ltd | Construction | 2022 |
| MDL Plant Ltd | Construction | 2016 |
| MDP Care Limited | Transport & logistics | 2017 |
| MDP Services Consulting Limited | Construction | 2013 |
| MEC Event Hire Ltd | Administrative & support | 2025 |
| Mecelex Limited | Construction | 2025 |
| Mechdyne Europe Limited | Information & communication | 2004 |
| Med-Pharm Healthcare Limited | Health & social care | 2009 |
| Med-Pharm Holdings Limited | Wholesale & retail | 2016 |
| MEL Property Ltd | Real estate | 2024 |
| Meltech Holdings Limited | Financial services | 2026 |
| Meltech Limited | Manufacturing | 1999 |
| Metropolis Catering Limited | Hospitality | 2012 |
| Mezz Floors UK Limited | Construction | 2007 |
| Mezzanine Floor Solutions Limited | Administrative & support | 2016 |
| Mezzanine Manufacturing Company Limited | Manufacturing | 2011 |
| MIA & BIA Ltd | Transport & logistics | 2018 |
| Michael Sale Architectural Surveyors Ltd | Professional & scientific | 2011 |
| Milky's Way Ltd | Information & communication | 2013 |
| Mini Athletics (Nottingham) Limited | Education | 2019 |
| Mini Athletics (ST Albans and Hatfield) Limited | Arts & recreation | 2018 |
| Mint Interior Solutions Ltd | Construction | 2016 |
| Miracle Tea Studios Ltd | Information & communication | 2016 |
| Mirror Mirror Fair N Tails LLP | | 2017 |
| Mitchell Motor Repairs Ltd | Wholesale & retail | 2014 |
| Mithus Cash & Carry Ltd | Wholesale & retail | 2025 |
| Mithus Continental Mart Ltd | Wholesale & retail | 2023 |
| MJS Auto Care Limited | Wholesale & retail | 2022 |
| Mjsm Fitness Group Ltd | Arts & recreation | 2020 |
| Mkta Limited | Professional & scientific | 2014 |
| MKV Properties Ltd | Real estate | 2020 |
| Mobile Coverage UK Limited | Information & communication | 2014 |
| Mobile Motor Engineers Limited | Wholesale & retail | 2000 |
| Molyneux-Summers Family Ltd | Professional & scientific | 2024 |
| Montage Partitions Limited | Manufacturing | 2009 |
| Moons Microtomy Ltd | Professional & scientific | 2023 |
| Moore (UK) Limited | Professional & scientific | 2004 |