| Maintenance Reliability Safety Instrumented Systems Limited | Professional & scientific | 2026 |
| Mair Arthur PUB Retail Ltd | Hospitality | 1994 |
| Mairsley Ltd | Extraterritorial | 2021 |
| Maislo Building Services Limited | Construction | 2019 |
| Maison & Vale Marketing Limited | Professional & scientific | 2025 |
| Maison 18TH Limited | Wholesale & retail | 2020 |
| Maison Alpha Ltd | Real estate | 2024 |
| Maison Cambria Limited | Real estate | 2015 |
| Maison DE Beaute (Pentyrch) Limited | Other services | 2017 |
| Maison DE Nuit Ltd | Wholesale & retail | 2025 |
| Maison Lentz Ltd | Information & communication | 2019 |
| Maison Maxie Ltd | Real estate | 2024 |
| Maison MAY Ltd | Real estate | 2023 |
| Maison Motors Ltd | Wholesale & retail | 2026 |
| Maison Noir Home & Beauty Ltd | Wholesale & retail | 2019 |
| Maison Quell Strategy Limited | Professional & scientific | 2025 |
| Maison Ruth Holdings Ltd. | Financial services | 2024 |
| Maison Velin Creative Limited | Professional & scientific | 2025 |
| Maisonmarvel Ltd | Information & communication | 2025 |
| Maisonmist Ltd | Wholesale & retail | 2025 |
| Maita Ltd | Health & social care | 2019 |
| Maize Blaze Limited | Hospitality | 2016 |
| Maizer Global Ltd | Wholesale & retail | 2025 |
| MAJ Trans Ltd | Wholesale & retail | 2019 |
| Majakel Ltd | Information & communication | 2012 |
| Majar Ltd | Transport & logistics | 2019 |
| Majestia Ltd | Wholesale & retail | 2024 |
| Majestic Commerce Ltd | Wholesale & retail | 2025 |
| Majestic Services Limited | Construction | 2019 |
| Majesticmarket Ltd | Wholesale & retail | 2025 |
| Majestix Ltd | Administrative & support | 2013 |
| Majesty Marketing Ltd | Information & communication | 2020 |
| Majic Bell Ltd | Other services | 2019 |
| Majid Contractors Ltd | Administrative & support | 2019 |
| Majistrar Ltd | Wholesale & retail | 2025 |
| Major Brushes Limited | Wholesale & retail | 1999 |
| Major Construction Services Limited | Professional & scientific | 2024 |
| Major GAS Plumbing & Heating Ltd | Other services | 2023 |
| Major Golf Events Ltd | Other services | 2023 |
| Major Mahil Services Limited | Real estate | 2006 |
| Majora Limited | Professional & scientific | 2017 |
| Majorblake Limited | Hospitality | 1984 |
| Majorteam Limited | Wholesale & retail | 2022 |
| MAK Desserts Ltd | Hospitality | 2026 |
| MAK Kassana Ltd | Administrative & support | 2020 |
| MAK Periodical Library Ltd | Information & communication | 2018 |
| Makan AL Samel Ltd | Wholesale & retail | 2025 |
| Makan Partnership UK Ltd | Real estate | 2019 |
| Makanova Ltd | Wholesale & retail | 2025 |
| Makber Ltd | Wholesale & retail | 2025 |
| Makbuildd Ltd | Construction | 2025 |
| Make a Claim Ltd | Professional & scientific | 2019 |
| Make Energy Great Again Ltd | Construction | 2025 |
| Make IT Happen Today Limited | Other services | 2018 |
| Make IT Perfect Limited | Hospitality | 2016 |
| Make ME Amazing Limited | Wholesale & retail | 2013 |
| Make Money Tomorrow Limited | Wholesale & retail | 2018 |
| Make Things Happen Ltd | Wholesale & retail | 2019 |
| Makeda International Consultancy Ltd | Professional & scientific | 2018 |
| Makeover Properties Ltd | Construction | 2024 |
| Maker's Club Ltd | Wholesale & retail | 2025 |
| Makers HUT Retail Ltd | Other services | 2020 |
| Maketown Limited | Real estate | 1978 |
| Makeup by Vaun Limited | Other services | 2014 |
| Maki Motors Ltd | Wholesale & retail | 2026 |
| Makin Atelier Ltd | Wholesale & retail | 2026 |
| Makingadent Limited | Professional & scientific | 2006 |
| Mako Data UK Limited | Information & communication | 2019 |
| Makoff Productions Ltd | Information & communication | 2025 |
| Makulan | Professional & scientific | 2024 |
| Makutu Marine Ltd | Financial services | 2020 |
| MAL Property Maintenance Ltd | Construction | 2022 |
| Malaay Appareell 99 Limited | Wholesale & retail | 2025 |
| Malaay Apparell 29 Limited | Wholesale & retail | 2025 |
| Malaay Apparell 55 Limited | Wholesale & retail | 2025 |
| Malaay Apparell 89 Limited | Wholesale & retail | 2025 |
| Malaay Apparell 99 Limited | Wholesale & retail | 2025 |
| Malabar Knots Ltd | Health & social care | 2026 |
| Malacara Limited | Information & communication | 2009 |
| Malacrino's Enterprises Limited | Manufacturing | 2024 |
| Malacrino's Products Limited | Manufacturing | 2024 |
| Malakeh Limited | Wholesale & retail | 2026 |
| Malaki Travel Ltd | Administrative & support | 2018 |
| Malaky Barber Ltd | Other services | 2024 |
| Malay Apparel 22 Limited | Wholesale & retail | 2025 |
| Malay Apparel 26 Limited | Wholesale & retail | 2025 |
| Malay Apparel 36 Limited | Wholesale & retail | 2025 |
| Malayalee Tharangam Limited | Hospitality | 2026 |
| Malazar Ltd | Other services | 2019 |
| Malbina Solutions Ltd | Wholesale & retail | 2021 |
| Malc Engineering Ltd | Professional & scientific | 2015 |
| Maldives Luxe Limited | Administrative & support | 2022 |
| Maldwyn Street (Cardiff) Limited | Households | 2016 |
| Male Lion Network Ltd | Wholesale & retail | 2025 |
| Malefant Fleets Ltd | Transport & logistics | 2024 |
| Malefant House Flat Management Company Limited | Households | 2014 |
| Malekin Law Limited | Professional & scientific | 2006 |
| Malen Appliances Repairs and Maintenance Ltd | Other services | 2025 |
| Malena Star Ltd | Professional & scientific | 2023 |
| Malenita PC | | 2018 |