| Maan O Salwa Ltd | Hospitality | 2025 |
| Maara Group Limited | Hospitality | 2023 |
| Maarushi Private Ltd | Wholesale & retail | 2022 |
| MAB Dental Limited | Health & social care | 2022 |
| Mabel and Bert Ltd | Professional & scientific | 2005 |
| Mabel Turner's Neighbourhood Fields Limited | Households | 2019 |
| Mabtraders Limited | Manufacturing | 2017 |
| Mac's Laser Engineering Limited | Manufacturing | 2021 |
| Mac's Transport (Northern) Limited | Manufacturing | 1973 |
| Mac's Truck Sales Limited | Manufacturing | 1996 |
| Macalpine Ventures Ltd | Information & communication | 2020 |
| Macaulay Travel Ltd | Administrative & support | 2017 |
| Machine Assist Limited | Other services | 2005 |
| Macintosh James and Partners Limited | Financial services | 2004 |
| Macleod's Specialist Ventilation Limited | Manufacturing | 2022 |
| Macmillan Estates Ltd | Administrative & support | 2001 |
| Macquarie Eight Limited | Professional & scientific | 2022 |
| Macrolarge Eco Consult Ltd | Information & communication | 2026 |
| Macs Truck (Rental Leasing) Co Ltd | Administrative & support | 2015 |
| Macy & Hugo’S Dog Grooming Ltd | Other services | 2020 |
| MAD Autocare Ltd | Wholesale & retail | 2018 |
| MAD Dawg Print Limited | Information & communication | 2013 |
| MAD for IT Promotions Ltd | Administrative & support | 2025 |
| MAD Yorkshire Ltd | Other services | 2020 |
| Madaan Property Limited | Real estate | 2026 |
| Maddie Farris Photography Limited | Professional & scientific | 2022 |
| Maddison Davis Limited | Administrative & support | 2024 |
| Made by A.N.D. Ltd | Professional & scientific | 2026 |
| Made by Cooper Ltd | Manufacturing | 2013 |
| Made Greater Limited | Information & communication | 2021 |
| Made in Crete Ltd | Professional & scientific | 2019 |
| Madhav Food Limited | Wholesale & retail | 2025 |
| Madhav Hotfood Private Ltd | Hospitality | 2018 |
| Madhav Private Ltd | Wholesale & retail | 2016 |
| Madiha H Ltd | Health & social care | 2020 |
| Madimo Express Limited | Wholesale & retail | 2023 |
| Madina Real Estate Ltd | Real estate | 2023 |
| MAE & BEE Ltd | Wholesale & retail | 2023 |
| Maesoiree Ltd | Professional & scientific | 2025 |
| Maevel Limited | Financial services | 2020 |
| MAF Home Designers Limited | Professional & scientific | 2024 |
| Mafa Healthcare Limited | Health & social care | 2016 |
| MAG Consultancy Services Limited | Health & social care | 2019 |
| Magis Serenity Ltd | Health & social care | 2024 |
| Magna Insurance Brokers Limited | Financial services | 2019 |
| Magnetawan Ltd | Wholesale & retail | 2020 |
| Magnum Food Ventures Ltd | Hospitality | 2024 |
| Magnum Trader ALF Ltd | Hospitality | 2025 |
| Magnum Trader Allentown Ltd | Hospitality | 2025 |
| Magnum Trader Ashfield Ltd | Hospitality | 2025 |
| Magnum Trading Bulwell Ltd | Hospitality | 2025 |
| Magnum Trading Leeds Ltd | Hospitality | 2024 |
| Magnum Trading M1 Ltd | Hospitality | 2022 |
| Magnum Trading M2 Ltd | Hospitality | 2024 |
| Magnum Trading Wakefield UK Ltd | Hospitality | 2022 |
| Magnum Trading WF Ltd | Wholesale & retail | 2020 |
| Magnum UK Holdings Ltd | Hospitality | 2025 |
| Magpie Design Ltd | Professional & scientific | 2014 |
| MAH Strategic Advisory Ltd | Professional & scientific | 2026 |
| MAH Systems Limited | Administrative & support | 2014 |
| Maharaja a Limited | Wholesale & retail | 2023 |
| Maheen Raja Limited | Hospitality | 2025 |
| Mahi Construction Services Ltd | Construction | 2013 |
| Mahi Investments Ltd | Real estate | 2026 |
| Mahimak Ltd | Health & social care | 2023 |
| Mahvision Limited | Wholesale & retail | 2024 |
| Mahw Ltd | Health & social care | 2020 |
| Mahzplace UK Ltd | Wholesale & retail | 2026 |
| MAI Consulting Ltd | Professional & scientific | 2025 |
| MAI Tech Solutions Ltd | Information & communication | 2024 |
| Mailingg Ltd | Real estate | 2020 |
| Maimuna CIC | Hospitality | 2024 |
| Maimuna Support Services Ltd | Health & social care | 2024 |
| Main Component Services Ltd | Professional & scientific | 2021 |
| Main Contract Services Limited | Administrative & support | 2008 |
| Maison Furnishings Limited | Wholesale & retail | 2006 |
| Maison Recruitment Ltd | Administrative & support | 2024 |
| Maison Tech Investments Ltd | Real estate | 2024 |
| Maison Tech Ltd | Administrative & support | 2022 |
| Maison Threads Limited | Wholesale & retail | 2014 |
| MAJ Huddersfield Ltd | Transport & logistics | 2023 |
| Majadera Health Care Services Ltd | Health & social care | 2020 |
| Majestic Consultancy Ltd | Health & social care | 2022 |
| Majestic Glory Ltd | Real estate | 2021 |
| Majestic House Limited | Professional & scientific | 2014 |
| Majestic Lens Ltd | Professional & scientific | 2025 |
| Majestic Roofing(Uk) Ltd | Construction | 2023 |
| Majesty PAY and Financial Services Ltd | Other services | 2019 |
| Majid Property Rentals Ltd | Real estate | 2025 |
| Major Energy Recruitment Limited | Administrative & support | 2023 |
| Major Essentials Limited | Wholesale & retail | 2023 |
| Major Group Holdings Limited | Professional & scientific | 2018 |
| Major Healthcare Growing Futures Limited | Real estate | 2024 |
| Major Optical Recruitment Limited | Administrative & support | 2020 |
| Major Primary Healthcare Limited | Administrative & support | 2020 |
| Major Recruitment (Construction) Limited | Administrative & support | 2018 |
| Major Recruitment (GPS) Ltd | Professional & scientific | 2013 |
| Major Recruitment Limited | Administrative & support | 2008 |
| Major Recruitment Managed Services Limited | Administrative & support | 2017 |
| Major Transport Ltd | Transport & logistics | 2023 |