| Long Term Design Ltd | Professional & scientific | 2021 |
| Lorax Couriers Ltd | Transport & logistics | 2019 |
| Lorraine Healthcare Ltd | Health & social care | 2016 |
| Lower Wilbury Farm Shop Ltd | Wholesale & retail | 2025 |
| LOX Farm Ltd | Real estate | 2015 |
| Loyal Trading (UK) Ltd | Wholesale & retail | 2004 |
| LP Display Ltd | Manufacturing | 2011 |
| LSL Care Ltd | Public administration | 2020 |
| LTA Concierge Ltd | Administrative & support | 2024 |
| LTG Motors Ltd | Wholesale & retail | 2023 |
| Lubemax Limited | Wholesale & retail | 2025 |
| Lubo Minchev Electrical Limited | Construction | 2026 |
| Lucy Raetz Oconnell Ltd | Health & social care | 2020 |
| Luxe Interior Doors Limited | Wholesale & retail | 2021 |
| Luxury Nails 67 Ltd | Other services | 2024 |
| Lymph Control Limited | Manufacturing | 2020 |
| M & R Floor Restorations Ltd | Construction | 2024 |
| M & R Properties (Beds) Ltd | Real estate | 2024 |
| M & R Wood Flooring Ltd | Construction | 2023 |
| M&H Direct Ltd | Wholesale & retail | 2013 |
| M&H Services Group Limited | Manufacturing | 2014 |
| M&Sc Properties Ltd | Real estate | 2021 |
| M-Power Energy Ltd | Manufacturing | 2018 |
| M. Hyland Motor Services Limited | Wholesale & retail | 2003 |
| M.E Holdings Limited | Financial services | 2018 |
| M.G. Roofing and SON Limited | Construction | 2006 |
| MA Palmer Ltd | Construction | 2026 |
| Machall Ltd | Wholesale & retail | 2025 |
| Madhan & Sethi Limited | Real estate | 2019 |
| Maganlaxmi Properties Ltd | Real estate | 2017 |
| Magical Property Limited | Real estate | 2018 |
| Magnet & Glow Ltd | Wholesale & retail | 2025 |
| Maguire and Woods Construction Limited | Extraterritorial | 1968 |
| Maiar Limited | Professional & scientific | 2001 |
| Maikology UK Limited | Professional & scientific | 2024 |
| MAK Industries Limited | Real estate | 2009 |
| Makermangb Ltd | Wholesale & retail | 2025 |
| Malgraves Fine Art Limited | Information & communication | 1995 |
| Maltings (Baldock) Limited(The) | Households | 1985 |
| Mandala Roots Ltd | Real estate | 2023 |
| Manpreet Limited | Financial services | 2018 |
| Mansion Capital Ltd | Real estate | 2018 |
| Manuka Media Limited | Professional & scientific | 2020 |
| Marabese & Bevan Limited | Wholesale & retail | 2023 |
| Marcitect Solutions Limited | Information & communication | 2025 |
| Margaret Lynn Limited | Information & communication | 1964 |
| Mariastouchcleaning Ltd | Administrative & support | 2025 |
| Market Square Capital Limited | Real estate | 2023 |
| Marketing Matters (1959) Limited | Wholesale & retail | 2014 |
| Marriotts Gymnastics Club | Arts & recreation | 2022 |
| Marsa Properties Ltd | Real estate | 2025 |
| Martinfield Limited | Administrative & support | 1982 |
| Martins 2018 Ltd | Wholesale & retail | 2019 |
| Maryam Khan's Art House Ltd | Other services | 2024 |
| Mata Homes Limited | Real estate | 2021 |
| Mata Investments Limited | Financial services | 2021 |
| Mathetical Systems Ltd | Information & communication | 2016 |
| Mathys Orthopaedics Limited | Wholesale & retail | 2004 |
| Matt Robertson Creative Ltd | Professional & scientific | 2015 |
| Matt Shawyer Consultancy Limited | Manufacturing | 2017 |
| Mauf Electrical Ltd | Construction | 2025 |
| Mauf Logistics Ltd | Transport & logistics | 2025 |
| MAY Fair Gardens (Arlesey) Management Co. Ltd | Households | 2026 |
| Maycroft 1974 Limited | Extraterritorial | 2013 |
| Mcdk Limited | Professional & scientific | 2016 |
| Mchale Rail Limited | Other services | 2016 |
| Mclean Scholfield Ltd | Financial services | 2016 |
| MD Clearances Ltd | Water & waste | 2026 |
| Mead Court (Abridge) Management Company Limited | Households | 1994 |
| Meadow Lodge Capital Limited | Real estate | 2019 |
| Mealing Roofing Limited | Construction | 2005 |
| Medezi Ltd | Education | 2023 |
| MEDIA3V Limited | Information & communication | 2008 |
| Medicalgogo Ltd | Administrative & support | 2016 |
| Mehdi Holdings Limited | Financial services | 2021 |
| Mehli Limited | Real estate | 2024 |
| Melle Venture UK Ltd | Other services | 2015 |
| Mentor Distribution Trustees Limited | Other services | 2025 |
| Mentorbest Limited | Real estate | 1976 |
| Merchant House Management Company Ltd | Households | 2016 |
| Merited Property Development Corporation Ltd | Financial services | 2026 |
| Metal Planet Limited | Wholesale & retail | 2000 |
| Method Financial Planning Limited | Financial services | 2020 |
| MG Residential Ltd | Real estate | 2019 |
| MH Connections Ltd | Energy | 2025 |
| Mi:Project Solutions Limited | Information & communication | 2017 |
| Michael Goding Holdings Limited | Real estate | 2016 |
| Michelle Scott Limited | Professional & scientific | 2013 |
| Mico Agency Limited | Information & communication | 2005 |
| Microcom Systems Limited | Administrative & support | 1985 |
| MID7 Limited | Extraterritorial | 2012 |
| MID8 Limited | Information & communication | 2023 |
| Middle Shots Ltd | Real estate | 2015 |
| Mids Pest Control Ltd | Administrative & support | 2016 |
| MIDSCOTTL247 International Limited | Health & social care | 2022 |
| Migdal & Sons Plumbing Limited | Construction | 2009 |
| Mighty Mode Ltd | Professional & scientific | 2025 |
| Milestone Design and Construction Consultants Ltd | Construction | 2018 |
| Milkandmango Ltd | Wholesale & retail | 2025 |
| Milled Ltd | Information & communication | 2011 |