| M&C Expres Limited | Administrative & support | 2022 |
| M&D Decorators Ltd | Manufacturing | 2021 |
| M&G Scaffolding Ltd | Construction | 2026 |
| M&K Traders Limited | Wholesale & retail | 2024 |
| M&M Evolution Ltd | Construction | 2016 |
| M&M Woodmakers Limited | Construction | 2011 |
| M&P Decor Ltd | Construction | 2023 |
| M&S Greater Properties Limited | Real estate | 2022 |
| M&V Ltd | Construction | 2020 |
| M&W Cleaning Services Limited | Administrative & support | 2020 |
| M. H. Moghadam Ltd | Transport & logistics | 2015 |
| M. Z. Tech Limited | Information & communication | 2009 |
| M.A.D. House Entertainment Ltd | Arts & recreation | 2007 |
| M.C. Render&Fixer Ltd | Construction | 2019 |
| M.P. Software Consultancy Services Limited | Information & communication | 2014 |
| M.P.K. Limited | Construction | 2025 |
| M.S Loft Creation Specialist Ltd | Construction | 2018 |
| M.S.D. Holdings Knightsbridge Limited | Real estate | 2025 |
| M24K Ltd | Hospitality | 2024 |
| MA Halal Butcher Ltd | Wholesale & retail | 2024 |
| MA9 Property Boutique Limited | Professional & scientific | 2012 |
| MAA Khodal Limited | Wholesale & retail | 2025 |
| Maahir Investment Limited | Real estate | 2020 |
| Maar Group Ltd | Financial services | 2022 |
| Mabani Property Management Ltd. | Real estate | 2000 |
| Mabu Sale Ltd | Wholesale & retail | 2021 |
| MAC Tech Stage Ltd | Information & communication | 2022 |
| Macha Studios Ltd | Information & communication | 2010 |
| Macka Properties Limited | Real estate | 2021 |
| Maclawrence Properties Ltd | Real estate | 2018 |
| Maclawrence Services Limited | Real estate | 2017 |
| Macroscope London Ltd | Information & communication | 2010 |
| Macs Enterprises Limited | Administrative & support | 2002 |
| Madalene Enterprises Ltd | Real estate | 2020 |
| Maddison Lake Ltd | Information & communication | 2023 |
| Maddison Spector Management Limited | Real estate | 2018 |
| Made by Adams Ltd | Professional & scientific | 2023 |
| Made NOT Born Ltd | Professional & scientific | 2012 |
| Madewithmina Ltd | Manufacturing | 2026 |
| Madika Homes Ltd | Real estate | 2023 |
| MAF Enterprises Limited | Wholesale & retail | 2021 |
| Mafe Limited | Wholesale & retail | 2022 |
| Magficoise Limited | Administrative & support | 2011 |
| Magic Motorcycle Ltd | Wholesale & retail | 2026 |
| Magicnorbert Sports Ltd | Information & communication | 2022 |
| Magna Star Ltd | Administrative & support | 2019 |
| Magnatruck Ltd | Transport & logistics | 2025 |
| Magnolia Analyst Relations Limited | Professional & scientific | 2009 |
| Magnum Express Transport UK Limited | | 1994 |
| Maguire-North Living Ltd | Construction | 2026 |
| Mahajan UK Limited | Wholesale & retail | 2000 |
| Mahakali Constuction Ltd | Construction | 2025 |
| Maharaja Construction Limited | Construction | 2019 |
| Mahiraj Properties Ltd | Real estate | 2023 |
| Mahoora London Jewelery Ltd | Wholesale & retail | 2025 |
| Mahya Food Ltd | Hospitality | 2025 |
| MAI Care Consultancy Limited | Health & social care | 2023 |
| Maid Tidy Services Limited | Administrative & support | 2016 |
| MAID2CLEAN (Domestic Services) Ltd | Other services | 2006 |
| Main Dealer Limited | Real estate | 2006 |
| Main-Street (Brews) Limited | Manufacturing | 2024 |
| Mainmoon Ltd | Hospitality | 2001 |
| Maintain Properties Ltd | Real estate | 2018 |
| Mainwood Limited | Water & waste | 1990 |
| Mairos Corporation Ltd | Manufacturing | 2019 |
| Maison DE Bethany Ltd | Wholesale & retail | 2015 |
| Maison Fine Jewellery Ltd | Wholesale & retail | 2025 |
| Maison Luze Events Limited | Hospitality | 2025 |
| Maitz Cakes Limited | Manufacturing | 2025 |
| MAJ Music Limited | Arts & recreation | 2018 |
| Majellin Limited | Real estate | 2025 |
| Majer Construction Ltd | Construction | 2018 |
| Majestic Hub Limited | Real estate | 2024 |
| Majidi Logistics Ltd | Transport & logistics | 2025 |
| Majkur Ltd | Water & waste | 2019 |
| Majlis Energy Development & Ventures Limited | Water & waste | 2026 |
| Majorfleet Limited | Households | 2007 |
| MAK Plus Capital Ltd | Financial services | 2026 |
| Makav Estates Ltd | Construction | 2025 |
| Makombe Productions UK Limited | Information & communication | 2009 |
| Malea Ltd | Construction | 2023 |
| Malfatti City Limited | Hospitality | 2007 |
| Malkan Estates Ltd | Real estate | 2017 |
| Malkan Investments Ltd | Real estate | 2018 |
| Malkan SS1 Ltd | Real estate | 2024 |
| Malketing Ltd | Information & communication | 2026 |
| Malmere Limited | Administrative & support | 2025 |
| Maltyverse Limited | Wholesale & retail | 2023 |
| MAM Small Limited | Professional & scientific | 2024 |
| Mama Bakery & Brunch Ltd | Manufacturing | 2026 |
| Mama Ghar Entertainment Limited | Arts & recreation | 2024 |
| Mambrino Ltd | Professional & scientific | 2022 |
| Mammiz Limited | Wholesale & retail | 2026 |
| MAN & MAN Associates Ltd | Education | 2015 |
| MAN Consulting Ltd | Information & communication | 2006 |
| Manaerica Ltd | Health & social care | 2015 |
| Manage Properties (Folkestone) Ltd | Real estate | 2023 |
| Management Projects Limited | Professional & scientific | 2015 |
| Manara Capital UK Ltd | Financial services | 2017 |
| Mander Solutions Ltd | Information & communication | 2019 |