| Micku Property Ltd | Real estate | 2021 |
| Micof Group Ltd | Wholesale & retail | 2026 |
| Microdermabrasion Co. Ltd | Other services | 2025 |
| Micromatters Ltd | Information & communication | 2010 |
| Microphone Hunt Ltd | Information & communication | 2021 |
| Microqnix-Uk Ltd | Wholesale & retail | 2006 |
| MID Third Limited | Professional & scientific | 2025 |
| Midair Studio Ltd | Professional & scientific | 2021 |
| Midas IT Projects Limited | Professional & scientific | 2016 |
| Middleham Square Limited | Administrative & support | 2026 |
| Middleton Taxis Limited | Administrative & support | 2024 |
| Mide & More Ltd | Construction | 2019 |
| Mideafrocaribbeanstore Limited | Wholesale & retail | 2026 |
| Midun Services Ltd | Administrative & support | 2025 |
| MIK Lions Limited | Information & communication | 2015 |
| Milano Image Limited | Wholesale & retail | 2013 |
| Miles Showell Limited | Information & communication | 2013 |
| Military Campaign Ltd | Wholesale & retail | 2025 |
| Military Mode Ltd | Information & communication | 2013 |
| Mill Road (Hertford) Management Company Limited | Households | 2006 |
| Mill Vale Management Limited | Households | 1981 |
| Millbrook Court RMC Limited | Households | 2025 |
| Mille Biotechnology UK Ltd | Extraterritorial | 2019 |
| Milleniumcars Limited | Wholesale & retail | 2018 |
| Millmoll Group Property Ltd | Administrative & support | 2010 |
| Millpenny Limited | Professional & scientific | 1982 |
| Millso Ltd | Information & communication | 2011 |
| Mimi Corporation Ltd | Administrative & support | 2020 |
| Mimmycare Ltd | Administrative & support | 2023 |
| MIN the Spin Ltd | Education | 2019 |
| Mina Sushi Ruislip Ltd | Hospitality | 2026 |
| Mind Focus Ltd | Health & social care | 2017 |
| MIND3 Ltd | Professional & scientific | 2010 |
| Mindandmuscleuk Ltd | Education | 2022 |
| Mindful Sounds Ltd | Other services | 2025 |
| Minerva Building Conservation Ltd | Construction | 2015 |
| Minerva Building Restoration Limited | Construction | 2003 |
| Minerva International Limited | Administrative & support | 2015 |
| Minerva Lodge Property Holdings Limited | Households | 2006 |
| Minerva Support Services Ltd | Professional & scientific | 2024 |
| Mini Minds Club Ltd | Wholesale & retail | 2023 |
| Mini Motives Ltd | Health & social care | 2026 |
| Mini Seeds Ltd | Health & social care | 2024 |
| Ministry of Medical Missions Limited | Health & social care | 2013 |
| Miniworks Ltd | Education | 2021 |
| Minnett Consultancy Ltd | Other services | 2023 |
| Minns Stores Ltd | Wholesale & retail | 2018 |
| Minster Connections Limited | Administrative & support | 2012 |
| Mint London Limited | Administrative & support | 2023 |
| Minustempo Limited | Administrative & support | 2023 |
| MIP Properties Ltd | Real estate | 2021 |
| Mirabaud RE Gatwick Campus Ltd | Financial services | 2023 |
| Mirabell Sailing Ltd | Extraterritorial | 2024 |
| Miranthekeloglan Ltd | Wholesale & retail | 2025 |
| Miranzi Healthcare Ltd | Public administration | 2019 |
| Mishima Studio Ltd | Professional & scientific | 2020 |
| Miskat Limited | Health & social care | 2012 |
| Miss Merry Ltd | Other services | 2011 |
| Missing Link Property Limited | Real estate | 2026 |
| Mission Plus Limited | Manufacturing | 2022 |
| Mission Point (London) RTM Company Limited | Real estate | 2022 |
| Mississippi Macdonald Music Ltd | Information & communication | 2022 |
| Mitchell Creative Limited | Professional & scientific | 2007 |
| Mitiu Limited | Wholesale & retail | 2023 |
| Mittee Catering Ltd | Hospitality | 2026 |
| Miyi Ltd | Professional & scientific | 2017 |
| MJH Property Maintenance Ltd | Households | 2019 |
| MJM Media Limited | Professional & scientific | 2018 |
| MK Business Investment Properties Ltd | Real estate | 2019 |
| MK Constructions Services Limited | Construction | 2016 |
| MK Law Solicitors Limited | Professional & scientific | 2009 |
| MK Marketing Solutions Ltd | Professional & scientific | 2010 |
| MK Rope Access Ltd | Construction | 2024 |
| MK-3 Barber Limited | Other services | 2024 |
| MK19 Properties Limited | Real estate | 2023 |
| MKA Enterprises Limited | Information & communication | 2010 |
| Mkhsd Company Ltd | Real estate | 2017 |
| Mklion Limited | Construction | 2024 |
| MKP Systems Limited | Information & communication | 2016 |
| MKS Mobile Catering Ltd | Hospitality | 2021 |
| ML Computer Services Limited | | 1988 |
| ML Radiology Ltd | Health & social care | 2025 |
| MLC Strategic Consulting Ltd | Professional & scientific | 2023 |
| MLJ Consulting Services Ltd | Information & communication | 2022 |
| MLK Bros Limited | Hospitality | 2024 |
| Mlsc UK Ltd | Real estate | 2025 |
| MM Delaneza Holding Ltd | Professional & scientific | 2024 |
| MM Prime Service Ltd | Health & social care | 2026 |
| MMC Ocal Limited | Hospitality | 2017 |
| MMM Building Services Ltd | Construction | 2023 |
| MMM2020 Ltd | Professional & scientific | 2020 |
| MNH Flowers Limited | Professional & scientific | 2018 |
| Moak Services Ltd | Health & social care | 2014 |
| Moas Consulting Limited | Information & communication | 2012 |
| Mobile Geek Squad Ltd | Wholesale & retail | 2018 |
| Mobile Waste Management Ltd | Water & waste | 2017 |
| Mobilenurs Ltd | Health & social care | 2018 |
| Mobixpert Limited | Wholesale & retail | 2019 |
| Modal Logic Limited | Professional & scientific | 2021 |
| Mode&Company Ltd | Wholesale & retail | 2021 |