| Luke Roper Holdings Limited | Professional & scientific | 2014 |
| Luke Roper Limited | Wholesale & retail | 2007 |
| Luke Roper Retail Limited | Wholesale & retail | 2009 |
| Luke Williamson Architect Limited | Professional & scientific | 2011 |
| LUKE1977 (Bicester) Limited | Financial services | 2026 |
| Lumi Consulting Ltd | Professional & scientific | 2015 |
| Lumie Aesthetics Ltd | Other services | 2026 |
| Lumina Partners Europe Limited | Administrative & support | 2023 |
| Luminosify Ltd | Wholesale & retail | 2021 |
| Luna Sales Consultancy Limited | Professional & scientific | 2023 |
| LUV Jeans Limited | Other services | 2015 |
| LUX Tanning and Beauty Ltd | Other services | 2022 |
| Luxe Glow Lounge Ltd | Other services | 2026 |
| Luxeonair Ltd | Administrative & support | 2026 |
| Luxicars (Hire) Limited | Transport & logistics | 1969 |
| Luxrapide Ltd | Professional & scientific | 2013 |
| Luxurious Cleaning (Oxon & Bucks) Ltd | Administrative & support | 2022 |
| LVM Silva Limited | Real estate | 2021 |
| LW Industries Ltd | Professional & scientific | 2025 |
| Lyceum Oxford CIC | Education | 2026 |
| Lyons Tyres Ltd | Wholesale & retail | 2018 |
| M & W Transport Ltd | Transport & logistics | 2013 |
| M Giles Building Contracts Limited | Construction | 2023 |
| M J Tech Limited | Wholesale & retail | 2008 |
| M J Wright Painting & Decorating Limited | Extraterritorial | 2003 |
| M Lewis Holdings Ltd | Financial services | 2026 |
| M Page Electrical Limited | Construction | 2003 |
| M S Instruments Limited | Manufacturing | 1967 |
| M Squared a Organic Beauty Ltd | Manufacturing | 2024 |
| M V Unique Property Investment Limited | Real estate | 2023 |
| M Warren Construction Ltd | Construction | 2020 |
| M&A Engineering and Planning Limited | Professional & scientific | 2024 |
| M&G Serenity Homecare Ltd | Public administration | 2024 |
| M&M Investment Property Limited | Real estate | 2023 |
| M-Werks Limited | Wholesale & retail | 2024 |
| M. E. Leech & Co Ltd | Professional & scientific | 2024 |
| M.B.G. Limited | Wholesale & retail | 1987 |
| M.J.M. Electrics Limited | Administrative & support | 1986 |
| M.S. Lawrence Limited | Extraterritorial | 2008 |
| M.W.Swinburne & Sons Limited | Professional & scientific | 1920 |
| M1LLION Ltd | Administrative & support | 2010 |
| M2M Transport Ltd | Transport & logistics | 2026 |
| M8SF CIC | Education | 2021 |
| MAB Property Maintenance Limited | Administrative & support | 2016 |
| Macdonald Hebditch & Co. Ltd. | Administrative & support | 1999 |
| Macorsi Logistics Ltd | Transport & logistics | 2022 |
| Macro Consult Ltd | Professional & scientific | 2022 |
| Macs Plant Limited | Construction | 2014 |
| MAD Flooring Supplies Ltd | Wholesale & retail | 2023 |
| Madcoms Ltd | Professional & scientific | 2019 |
| Made in Chiswick Ltd | Real estate | 2023 |
| Madson Black Limited | Wholesale & retail | 2002 |
| Madube Care Limited | Health & social care | 2013 |
| Madura (UK) Limited | Construction | 2022 |
| Magara Law Limited | Professional & scientific | 2020 |
| Maggetti Limited | Arts & recreation | 2021 |
| Maggs Estate Management Limited | Construction | 2021 |
| Magnetic Brothers Ltd | Real estate | 2023 |
| Maha Lakshmi Deal Partners Ltd | Hospitality | 2024 |
| Maha Lakshmi Fortune Ltd | Real estate | 2024 |
| Maha Lakshmi Investment LLP | | 2023 |
| Mahon Automation Limited | Professional & scientific | 2023 |
| Mahosam Ltd | Hospitality | 2024 |
| Mahov Limited | Construction | 2020 |
| Main Street Goods Ltd | Wholesale & retail | 2025 |
| Maison DU Cozi Ltd | Real estate | 2021 |
| Major Impact Ltd | Extraterritorial | 2024 |
| Majors Decorating Ltd | Construction | 2020 |
| Maka Limited | Real estate | 2025 |
| MAL & ISH Properties Ltd | Real estate | 2024 |
| Malee Limited | Hospitality | 2019 |
| Malik Property Enterprises Ltd | Real estate | 2024 |
| Maltby Way Property Management Ltd | Households | 2012 |
| Mamaa's Market Limited | Wholesale & retail | 2025 |
| Mamak Dental Limited | Health & social care | 2019 |
| Manarco Ltd | Wholesale & retail | 2025 |
| Mango Knowledge Solutions LLP | | 2016 |
| Mania Breaks Ltd | Wholesale & retail | 2024 |
| Mania Holdings Ltd | Wholesale & retail | 2025 |
| Manor Farm Barns Somerton Limited | Households | 2004 |
| Manor Gardens (CN) Ltd | Administrative & support | 2014 |
| Manston Consulting Ltd | Professional & scientific | 2016 |
| Maple Grove (Hackbridge) Management Limited | Households | 2018 |
| Maple Leys Consulting Ltd | Professional & scientific | 2014 |
| Marcin S Trans Ltd | Transport & logistics | 2016 |
| Marco Mura Limited | Health & social care | 2026 |
| Marfield Projects Ltd | Professional & scientific | 2025 |
| Margherita Tanzarella Limited | Health & social care | 2025 |
| Mari Holloway Consultancy Limited | Professional & scientific | 2013 |
| Maria Skoutari Architects Ltd | Information & communication | 2022 |
| Mariah Professional Cleaning Services Limited | Administrative & support | 2025 |
| Marian Lungu Logistic Ltd | Wholesale & retail | 2022 |
| Marilyn's Solutions Ltd | Manufacturing | 2020 |
| Mark a. N. Broderick & Associates Ltd | Professional & scientific | 2009 |
| Mark II Limited | Construction | 1993 |
| Mark Stone Homes Limited | Construction | 2012 |
| Mark Watson Limited | Information & communication | 2022 |
| Market House Dental Practice Limited | Health & social care | 2016 |
| Market Lane Phase II Management Limited | Households | 1990 |
| Market Square Dental Ltd | Health & social care | 2014 |