| Kinsman Estates Limited | Real estate | 1997 |
| Kore Consulting UK Limited | Information & communication | 2008 |
| KP Property Services Limited | Construction | 2008 |
| KRAKEN21 Holding Ltd | Construction | 2024 |
| L C Global Elite Limited | Financial services | 2010 |
| L Lucas JNR Limited | Construction | 2015 |
| L Meredith Services Ltd | Professional & scientific | 2021 |
| LDC Heating Limited | Construction | 2015 |
| Learn Automation Ltd | Information & communication | 2019 |
| LEE Construction Services Limited | Professional & scientific | 2007 |
| LEE Valley Carpentry & Joinery Ltd | Construction | 2020 |
| Leiselle Bristow Design Limited | Arts & recreation | 2007 |
| Levato Enterprise Ltd | Hospitality | 2023 |
| LG Heating & Plumbing Ltd | Construction | 2015 |
| LGL Brick Work Ltd | Construction | 2022 |
| Libman Brands UK Ltd. | Manufacturing | 1968 |
| Lightning Systems and Terminals Ltd | Wholesale & retail | 2018 |
| Limekiln Road Properties Limited | Real estate | 2019 |
| Lincoln Motorcycle Repair Ltd | Wholesale & retail | 2024 |
| Logic Audio Visual Limited | Professional & scientific | 2020 |
| London & East Coast Securities Limited | Financial services | 1971 |
| London CAB Rentals Ltd | Administrative & support | 2020 |
| London Express Logistics Ltd | Transport & logistics | 2018 |
| London Fire and Electrical Limited | Construction | 2019 |
| London Graphic Systems Limited | Information & communication | 2008 |
| London Sneaker School Ltd | Manufacturing | 2020 |
| Lonwale Developments Ltd | Real estate | 2011 |
| Lw-Kelvin Consulting Ltd | Professional & scientific | 2025 |
| LX Solutions Limited | Information & communication | 2007 |
| Lyons Builders Ltd | Professional & scientific | 2016 |
| M & H Boiler Spares Limited | Wholesale & retail | 2017 |
| M J Willow Care Limited | Agriculture & fishing | 2023 |
| M M Associates (Holdings) Limited | Professional & scientific | 2003 |
| M T Woods Limited | Construction | 2009 |
| M'N'T Curtains and Blinds Ltd | Manufacturing | 2012 |
| M.G Heating Installs Ltd | Construction | 2022 |
| M.J.V. & Co. Accountants Limited | Professional & scientific | 2012 |
| MA Properties Group Ltd | Real estate | 2026 |
| Maaf Facility Services Limited | Information & communication | 2020 |
| Macmillan Way Management Company Limited | Households | 2002 |
| Magnit Property Ltd | Real estate | 2022 |
| Maheep Khalsa Ltd | Health & social care | 2024 |
| MAI Thai Kitchen (Cheshunt) Ltd | Hospitality | 2023 |
| Maid Property Investment Ltd | Real estate | 2024 |
| MAJ Solutions Limited | Construction | 2013 |
| MAL Construction Ltd | Construction | 2010 |
| Malik & Kingsley Properties Ltd | Construction | 2025 |
| Managed Print Compare Limited | Wholesale & retail | 2017 |
| Manestream Holdings Limited | Real estate | 2016 |
| Manor Farm Road (Blocks a B C & D) Flat Management Company Limited | Households | 1996 |
| Manor Farm Road (Blocks E F G & H) Flat Management Company Limited | Households | 1996 |
| Manor Farm Road Residents Association Limited | Households | 1999 |
| Manron Solutions Ltd | Health & social care | 2014 |
| Mapletop Estates Ltd | Real estate | 2002 |
| Mary Shoes Limited | Wholesale & retail | 1996 |
| Masella Enterprises Ltd | Professional & scientific | 2013 |
| Matcha Monkey Ltd | Wholesale & retail | 2020 |
| Matei Decorating Ltd | Other services | 2015 |
| Materials & Commodities Ltd | Water & waste | 2020 |
| Matrix Innovations Limited | Manufacturing | 2001 |
| Matt Miller Consultancy Limited | Professional & scientific | 2014 |
| Matthew J Allen Ltd | Construction | 2009 |
| Med-Inspire Pharma Ltd | Wholesale & retail | 2022 |
| Meggaclean Limited | Administrative & support | 2012 |
| Memon International Limited | Construction | 1997 |
| Michalis Ltd | Health & social care | 2012 |
| Michie Developments Ltd | Real estate | 2018 |
| Micromain Services Ltd | Administrative & support | 1999 |
| MID Point 4 Women Limited | Health & social care | 2015 |
| Milburn Press Investments Limited | Real estate | 2025 |
| Millers Green (NO. 1) Management Company Limited | Households | 1987 |
| Millers Green (NO. 2) Management Company Limited | Households | 1987 |
| Millers Green (NO. 3) Management Company Limited | Households | 1987 |
| Minerva Team Sports Ltd | Wholesale & retail | 2024 |
| Minetra Ltd | Wholesale & retail | 2025 |
| MJD Corporate Holdings Limited | Financial services | 2020 |
| MJR Fabrications Limited | Manufacturing | 2008 |
| Mkcfs Limited | Information & communication | 2008 |
| MKD Builders Ltd | Real estate | 2019 |
| Mlmpcs Limited | Professional & scientific | 2013 |
| MM Associates Limited | Financial services | 1979 |
| Mobile Assist Consultants Limited | Administrative & support | 2009 |
| Mobile Smart Mechanics Ltd | Wholesale & retail | 2019 |
| Mobile Sweeper Mechanics Ltd | Manufacturing | 2011 |
| Modular Construction Ltd | Construction | 2019 |
| Mojid Properties Limited | Real estate | 2024 |
| Monaghan Executive Cars Limited | Transport & logistics | 2015 |
| Moonstage Ltd | Information & communication | 2018 |
| Mooretan Limited | Other services | 2023 |
| Moss Property Holdings Ltd | Real estate | 2022 |
| MP Treatment UK Ltd | Construction | 2014 |
| MR Box Limited | Administrative & support | 2020 |
| Mulminster Limited | Financial services | 1986 |
| Mymms Drive Limited | Real estate | 2017 |
| Myrtle Care Providers Limited | Health & social care | 2017 |
| N C D Ground Maintenance Services Ltd | Administrative & support | 2009 |
| N J S Designs Limited | Arts & recreation | 1994 |
| Naa's Grocery Store Ltd | Wholesale & retail | 2024 |
| NAB Car Sales Limited | Wholesale & retail | 2015 |
| NCS (Middlesex) Limited | Information & communication | 2017 |