| Luton Brewing Co Ltd | Hospitality | 2021 |
| LUX Barbershop Limited | Other services | 2019 |
| LUX Strategy Partners Ltd | Construction | 2025 |
| Luxury Golf Travel Ltd | Extraterritorial | 2020 |
| LW Theatre Training Limited | Education | 2020 |
| M & a Consulting Limited | Professional & scientific | 1992 |
| M & D Gent Farms Ltd | Agriculture & fishing | 2023 |
| M & D Gent Services Ltd | Information & communication | 2016 |
| M & D PUB Group Ltd | Hospitality | 2019 |
| M Allwright Plumbing and Property Services Ltd | Construction | 2023 |
| M N P Building Services Limited | Construction | 2011 |
| M R Langdon Limited | Construction | 2025 |
| M&D Accommodations Ltd | Real estate | 2018 |
| M.S.Engr Limited | Professional & scientific | 2024 |
| M2S Cleaning Services Limited | Other services | 2017 |
| MAC and Doon Ltd | Information & communication | 2021 |
| Mackenzie Miller Consulting Limited | Professional & scientific | 2011 |
| Mackers Inns Ltd | Hospitality | 2026 |
| Mackesy Limited | Construction | 2021 |
| MAD About Mantrailing Ltd | Arts & recreation | 2024 |
| Madd Inc Ltd | Arts & recreation | 2019 |
| Maddy's Bakery Ltd | Manufacturing | 2018 |
| Made With Knots of Love Ltd | Wholesale & retail | 2024 |
| Magic HAT FX Ltd | Professional & scientific | 2010 |
| Magical Grotto's Limited | Arts & recreation | 2020 |
| MAID2CLEAN(BEDS & North Herts) Ltd | Administrative & support | 2012 |
| Maintain Cleaning Services Limited | Administrative & support | 2017 |
| Makjo Ltd | Transport & logistics | 2026 |
| Manhattan Historic Motorsport Ltd | Wholesale & retail | 2021 |
| Manning Technology Consulting Limited | Information & communication | 2026 |
| Manor Farm Lakes Ltd | Financial services | 2018 |
| Manor Farm Units Ltd | Real estate | 2018 |
| Mapletree Catering Ltd | Hospitality | 2007 |
| Maps United Ltd | Information & communication | 2011 |
| Marian&Son Ltd | Construction | 2017 |
| Mark Brown IT Services Limited | Information & communication | 2026 |
| Mark Gent Services Ltd | Information & communication | 2011 |
| Mark Orme Haulage Ltd | Transport & logistics | 2024 |
| Markell Ltd | Manufacturing | 2022 |
| Marnov Consultancy Limited | Health & social care | 2015 |
| Marquee Brickwork Ltd | Construction | 2022 |
| Marquee Scaffolding Ltd | Construction | 2024 |
| Martin Craswell & Co Limited | Information & communication | 2016 |
| Marvel Contractors Limited | Construction | 1974 |
| Marwaha Property Ltd | Real estate | 2021 |
| Marya Logistics Limited | Transport & logistics | 2012 |
| Masala Trunk Ltd | Hospitality | 2026 |
| Maskot Projects Ltd | Construction | 2022 |
| Maxim Rehabilitation Ltd | Health & social care | 2012 |
| Maximus Productions Ltd. | Arts & recreation | 2014 |
| MB Brickwork Construction Limited | Construction | 2020 |
| Mbvr Ltd | Wholesale & retail | 2012 |
| MC Expert Engineering Ltd | Construction | 2024 |
| MD Plantweld Limited | Manufacturing | 2020 |
| MDN Supplies Limited | Wholesale & retail | 2012 |
| Meadowcroft Foodservice Limited | Wholesale & retail | 2013 |
| Medical Liaison & Consulting Office Limited | Health & social care | 2007 |
| Mehabilitation Ltd | Health & social care | 2023 |
| Mei's Garden Ltd | Hospitality | 2024 |
| Meimei 99886 Limited | Hospitality | 2025 |
| Memcon Limited | Manufacturing | 2007 |
| Mevaris London Limited | Wholesale & retail | 2020 |
| MFR Assessments Ltd | Financial services | 2025 |
| MGM Property Developments Limited | Construction | 2012 |
| Mh&W Ltd | Health & social care | 2023 |
| MI Shannon Properties Ltd | Real estate | 2021 |
| MID Beds Locksmiths Limited | Manufacturing | 2013 |
| Middleton Bespoke Joinery Limited | Construction | 2013 |
| Mill Stream Developments (Meldreth) Limited | Construction | 2017 |
| Millership Events Limited | Administrative & support | 2018 |
| Millie's Games Limited | Manufacturing | 2024 |
| Mimalulu Ltd | Arts & recreation | 2018 |
| Mind Science Media Limited | Information & communication | 2010 |
| Miresa Limited | Wholesale & retail | 2013 |
| Mistakes Were Made Ltd | Arts & recreation | 2024 |
| Mister BIT Ltd | Construction | 2025 |
| Mitsui Yamaha Limited | Wholesale & retail | 2011 |
| MJS Painters & Decorators Limited | Construction | 2011 |
| Mkmg Ltd | Wholesale & retail | 2023 |
| MKR Productions Limited | Information & communication | 2008 |
| MMV Bubu Limited | Transport & logistics | 2016 |
| MO Health Care Services Limited | Health & social care | 2014 |
| Modal Property Solutions Limited | Construction | 2018 |
| Modula-Ai Limited | Information & communication | 2023 |
| Mokj Consulting Ltd | Professional & scientific | 2025 |
| Molqi Ltd | Wholesale & retail | 2022 |
| Moma Solutions Limited | Hospitality | 2017 |
| Momentum Fitness & Conditioning Ltd | Health & social care | 2025 |
| Monamy Trustees Limited | Professional & scientific | 2014 |
| MOO MOO Investments Limited | Real estate | 2024 |
| Moond Ltd | Professional & scientific | 2021 |
| Moonrock Boombox Limited | Arts & recreation | 2013 |
| Moore Television Limited | Information & communication | 2013 |
| Moozlebug Ltd | Information & communication | 2018 |
| Morrison Service Management Limited | Information & communication | 2009 |
| Morsman and Tyler Limited | Administrative & support | 2020 |
| Mosaic Workshop Ltd | Wholesale & retail | 2022 |
| Motorcycle Solutions (Europe) Limited | Wholesale & retail | 2023 |
| Motorcycle Solutions Limited | Wholesale & retail | 2014 |
| Mousa Consultancy Limited | Professional & scientific | 2014 |