| MIQ Solutions Ltd | Information & communication | 2012 |
| Mirel Leisure Limited | Administrative & support | 2018 |
| Mirror Clean Ltd | Administrative & support | 2019 |
| Misembodied Ltd | Wholesale & retail | 2023 |
| Mishee Properties Limited | Real estate | 2021 |
| Miss. N P Ltd | Other services | 2022 |
| Mistique Motors Ltd | Wholesale & retail | 2025 |
| Mitash Limited | Administrative & support | 2017 |
| Mitcham Bookkeeping Ltd | Professional & scientific | 2024 |
| Mitcham Junction Press Limited | Manufacturing | 1966 |
| Mitchell & Co. Innotech (UK) Limited | Wholesale & retail | 2026 |
| Mitchley Developments Limited | Construction | 2019 |
| Mithra Technologies Limited | Information & communication | 2023 |
| Mitkon Solutions Limited | Information & communication | 2024 |
| MJ & Sons Properties Ltd | Real estate | 2022 |
| MJ Plumbing, Heating and Maintenance Ltd | Construction | 2025 |
| Mjan Ltd | Administrative & support | 2025 |
| MJB 1 Ltd | Other services | 2017 |
| MJB Distribution Ltd | Wholesale & retail | 2018 |
| Mjjc Integrated Systems Ltd | Administrative & support | 2018 |
| MJS Scaffolding (Surrey) Ltd | Construction | 2022 |
| MK Fresh Ltd | Wholesale & retail | 2022 |
| MK Health and Education Service Ltd | Information & communication | 2024 |
| MK Monkey Property Ltd | Real estate | 2021 |
| MK Overseas Enterprise Ltd | Wholesale & retail | 2024 |
| MK Smiles Excellence Ltd | Health & social care | 2026 |
| MK Trading Ltd Limited | Construction | 2016 |
| MKB Flooring Ltd | Construction | 2015 |
| MKL Carpentry Ltd | Construction | 2025 |
| MKR Healthcare Ltd | Health & social care | 2023 |
| MKV Builders Ltd | Construction | 2017 |
| ML Eco Solutions Limited | Water & waste | 2025 |
| Mlnl Consulting Ltd | | 2014 |
| MM GP Services Ltd | Health & social care | 2021 |
| Mm-Ict Limited | Information & communication | 2010 |
| Mm-Lkb Limited | Real estate | 2023 |
| MMA Professional Services Limited | Health & social care | 2026 |
| MMA Renovations Ltd | Construction | 2025 |
| MMH Building Services Limited | Construction | 2008 |
| MMW Developments Ltd | Real estate | 2022 |
| MN Management Support Ltd | Professional & scientific | 2025 |
| Mnnga Ltd | Wholesale & retail | 2016 |
| MOA Works Limited | Professional & scientific | 2025 |
| Mobi Trims Ltd | Other services | 2022 |
| Mobile BIT Sutton Ltd | Other services | 2016 |
| Mobile DJ Mastery Ltd | Education | 2022 |
| Mobile Shop N More Ltd | Other services | 2023 |
| Mobile Shop Sutton Ltd | Wholesale & retail | 2021 |
| Mobile Support Services Limited | Administrative & support | 2009 |
| Mobile Tyre Repair Ltd | Wholesale & retail | 2026 |
| Mobile Tyres Surrey Ltd | Wholesale & retail | 2021 |
| Mobilemech Autocare Limited | Wholesale & retail | 2025 |
| Mochisons Ltd | Other services | 2022 |
| Mocka Fashion Limited | Wholesale & retail | 2023 |
| Mocka Homes Limited | Real estate | 2025 |
| Modelling Risk Technology Ltd | Information & communication | 2013 |
| Modern Boiler Limited | Construction | 2021 |
| Modern Lifts Ltd | Construction | 2024 |
| Modern Tenancy Ltd | Households | 2018 |
| Modernus Decoration Projects Ltd | Construction | 2021 |
| Modest Edit Ltd | Wholesale & retail | 2025 |
| Modidi Ltd | Construction | 2020 |
| Modify Building Services Ltd | Construction | 2024 |
| Modiv Ltd | Administrative & support | 2016 |
| Modulan Limited | Information & communication | 2013 |
| Moevo Software Ltd | Information & communication | 2019 |
| Moiz Medical Services Limited | Health & social care | 2023 |
| Moksh Consulting Ltd | Administrative & support | 2014 |
| Molesey Lofts Construction Ltd | Construction | 2023 |
| Momentum Valeting Limited | Administrative & support | 2012 |
| Monaco Block Management Ltd | Real estate | 2021 |
| Monali's Dance Studio Ltd | Arts & recreation | 2024 |
| Monarica Limited | Real estate | 2022 |
| Mongolian Buddha Centre Ltd | Education | 2025 |
| Monkey Puzzle Day Nurseries (Sutton) Limited | Health & social care | 2021 |
| Monster Drainage Limited | Construction | 2025 |
| Monster Mentality Ltd | Education | 2023 |
| Monster Worldwide Limited | Administrative & support | 1985 |
| Monsterkil Construction Ltd | Construction | 2025 |
| Montford Court (Sutton) Management Company Limited | Real estate | 1978 |
| Montreaux Design & Build Ltd | Real estate | 2020 |
| Montrose Management Services Ltd | Professional & scientific | 2020 |
| Moodforcode UK Ltd | Information & communication | 2022 |
| Moodia App Limited | Information & communication | 2024 |
| Mooli Elegant Ltd | Health & social care | 2023 |
| Moorhouse Heating & Plumbing Limited | Construction | 2026 |
| Moorland Garden Ltd | Health & social care | 2022 |
| Moran Homecare Ltd | Health & social care | 2017 |
| Morane Trading Co Ltd | Administrative & support | 2026 |
| Morecello Ltd | Professional & scientific | 2016 |
| Morethanwood Ltd | Manufacturing | 2021 |
| Morevan Logistics Limited | Transport & logistics | 2019 |
| Morhys Limited | Information & communication | 2015 |
| Morina Gentleman Grooming 1988 Ltd | Other services | 2025 |
| Morosanu Transport Ltd | Transport & logistics | 2024 |
| Mosaic CSR Ltd | Other services | 2021 |
| Moto Build Racing Ltd | Manufacturing | 2012 |
| Motorbey Limited | Extraterritorial | 2024 |
| Motormood Ltd | Wholesale & retail | 2025 |
| Motspur Park Community Football Club C.I.C. | Arts & recreation | 2023 |