| Mablak Ltd | Wholesale & retail | 2020 |
| MAC Estate Holdings Ltd | Real estate | 2023 |
| MAC Tipping Limited | Transport & logistics | 2005 |
| Maccapps Ltd | Information & communication | 2018 |
| Mace Engineering Design Limited | Professional & scientific | 2022 |
| Macgregor Hope Associates Limited | Professional & scientific | 2015 |
| Machinery Catalyst Ltd | Professional & scientific | 2025 |
| Mack Capital Partners Limited | Real estate | 2016 |
| Mack Engineers Ltd | Professional & scientific | 2020 |
| Mack Leisure Limited | Hospitality | 2019 |
| Mackenzie Carter Recruitment Limited | Professional & scientific | 1999 |
| Mackenzie Financial Planning Limited | Financial services | 2010 |
| Macro Global Group Limited | Financial services | 2024 |
| Macro Global Holdings Limited | Administrative & support | 2011 |
| Macro Packaging (Sheerness) Limited | Manufacturing | 2026 |
| Macro Packaging Limited | Administrative & support | 2004 |
| MAD Removals Limited | Transport & logistics | 2025 |
| Madcity Print Limited | Manufacturing | 2014 |
| Made AV Ltd | Information & communication | 2015 |
| Made in Cobham Ltd | Wholesale & retail | 2025 |
| Made in Plastic Limited | Manufacturing | 2025 |
| Madhav-Meenakshi Management Limited | Real estate | 2018 |
| Madl Consultancy Ltd | Health & social care | 2019 |
| Madzaboutbeauty Ltd | Other services | 2025 |
| Mae-Jah Munch Ltd | Hospitality | 2025 |
| Maebil Lettings Ltd | Real estate | 2021 |
| Maelstrom S E Ltd | Construction | 2015 |
| Maffei Property Holdings Limited | Real estate | 2026 |
| Magee Gammon Audit LLP | | 2001 |
| Magee Gammon Corporate Audit Limited | Professional & scientific | 2024 |
| Magee Gammon Corporate Limited | Administrative & support | 2001 |
| Magee Gammon Financial Planning Limited | Financial services | 2014 |
| Magha Group Limited | Real estate | 2024 |
| Maghoo Legacy Holdings Ltd | Real estate | 2022 |
| Magic Allstars Ltd | Arts & recreation | 2025 |
| Magna Riverside Management Company Ltd | Households | 2018 |
| Magnani Solutions Ltd | Construction | 2019 |
| Magnum Opus Group (UK) Limited | Professional & scientific | 2023 |
| Magpie Farm Management Company Ltd | Construction | 2015 |
| Magu Conglomerate Ltd | Wholesale & retail | 2024 |
| Mahant Estates Limited | Real estate | 2018 |
| Mahavir Assets Ltd | Real estate | 2022 |
| Maheeda Grey Carers Ltd | Health & social care | 2023 |
| Mahers Model Makers Ltd | Professional & scientific | 2020 |
| Mahira Homes Limited | Construction | 2016 |
| Mahk Services Limited | Financial services | 2019 |
| Mahko Impex Limited | Other services | 2018 |
| Mahoney Midland Enterprises Ltd | Professional & scientific | 2011 |
| Mahé Ltd | Wholesale & retail | 2019 |
| MAI Day Recruitment Services Limited | Professional & scientific | 2001 |
| MAID2CLEAN (North Devon & Cornwall) Limited | Other services | 2024 |
| Maida Vale Leisure Limited | Hospitality | 2016 |
| Maidstone Autocentre (Holdings) Limited | Financial services | 2020 |
| Maidstone Autocentre Limited | Administrative & support | 1997 |
| Maidstone Literary Festival CIC | Information & communication | 2024 |
| Maidstone Osteopathic Practice Limited | Health & social care | 2014 |
| Mailliwear Limited | Construction | 2015 |
| Main Construction Services Ltd | Other services | 2018 |
| Maintenance Domestic Services Ltd | Construction | 2022 |
| Maintenix Limited | Professional & scientific | 2025 |
| Maiona UK Limited | Manufacturing | 2012 |
| Majestic Mart Ltd | Wholesale & retail | 2025 |
| Majikle Creations Limited | Health & social care | 2017 |
| Majju Robotics Ltd | Manufacturing | 2025 |
| Major Carpentry and Construction Ltd | Construction | 2023 |
| Major Property Investments Ltd | Real estate | 2024 |
| Major Rail Solutions Ltd | Construction | 2019 |
| MAK Cafe Ltd | Hospitality | 2020 |
| Makaan Developments Ltd | Real estate | 2021 |
| Makarios Media Services Limited | Professional & scientific | 2024 |
| Makenews Limited | Extraterritorial | 2022 |
| Makingtheday Ltd | Administrative & support | 2014 |
| Mako Studios Limited | Information & communication | 2024 |
| MAL3XD Ltd | Health & social care | 2023 |
| Malindi Media Ltd | Information & communication | 2022 |
| Mallard and Drake Limited | Administrative & support | 2009 |
| Malone Formwork Ltd | Construction | 2016 |
| Malpas-Green Ltd | Professional & scientific | 2025 |
| Malt Rail Solutions Ltd | Transport & logistics | 2019 |
| Malthouse Products Limited | Wholesale & retail | 1993 |
| MAM (Southern House) Limited | Real estate | 2016 |
| Mama Joy's Jerk Kitchen Ltd | Hospitality | 2025 |
| Mama's HUT Ltd | Hospitality | 2022 |
| Mammoth Signs & Graphics Ltd | Professional & scientific | 2023 |
| Manabuild Ltd | Construction | 2025 |
| Manakamana Ashford Limited | Hospitality | 2017 |
| Mandeville Consultancy Ltd | Information & communication | 2021 |
| Mandrake Advisory Ltd | Professional & scientific | 2024 |
| Mandy Builders Ltd | Construction | 2019 |
| Mangrove Conservation UK Ltd | Agriculture & fishing | 2024 |
| Manie Financials Ltd | Professional & scientific | 2025 |
| Manifest Aesthetics Ltd | Other services | 2025 |
| Manley Farms Ltd | Agriculture & fishing | 2021 |
| Manna Life Limited | Health & social care | 2025 |
| Manna Retail Limited | Wholesale & retail | 2026 |
| Mannings Clothes Care Limited | Other services | 2015 |
| Manny Consultants Ltd | Professional & scientific | 2024 |
| Mans Rail Ltd | Construction | 2015 |
| Mansa Consulting Limited | Financial services | 2023 |
| Mansfield Apartments Ltd | Real estate | 2022 |