| Mikani Group Limited | Professional & scientific | 2025 |
| Mikani Holdings Limited | Financial services | 2025 |
| Mikani Stratum 1 Limited | Professional & scientific | 2025 |
| Mikani Stratum 2 Limited | Professional & scientific | 2025 |
| Mikani Stratum 3 Limited | Professional & scientific | 2025 |
| Mike Bartram Limited | Professional & scientific | 2007 |
| Milan Majithia Limited | Health & social care | 2022 |
| Miles Driving School Limited | Education | 2022 |
| Miles Transport Limited | Administrative & support | 2015 |
| Milestone Group Citadel Ltd | Real estate | 2025 |
| Milestone Sales Ltd | Real estate | 2020 |
| Milestones Management Co. Limited | Hospitality | 1995 |
| Milford Dental Centre Limited | Health & social care | 2018 |
| Mili Property Ltd | Construction | 2025 |
| Mill GAP Flat Management Company Limited | Households | 1979 |
| Mill Road Wood UK Ltd | Construction | 2025 |
| Millennium Crofts Limited | Agriculture & fishing | 2018 |
| Miller's Court Tenants Limited | Households | 1970 |
| Millie Buckle Limited | Professional & scientific | 2024 |
| Milligan Tennis Limited | Arts & recreation | 2013 |
| Milne Carpentry Limited | Construction | 2008 |
| Milnthorpe 22 Limited | Households | 2023 |
| Milnthorpe Gardens Residents Association Limited | Households | 1971 |
| Milton Futures Ltd | Real estate | 2018 |
| Mimas Dessert Ltd | Manufacturing | 2025 |
| Mimstar Consultancy Limited | Information & communication | 2007 |
| Mina Bassily Limited | Health & social care | 2021 |
| Minati Limited | Wholesale & retail | 2025 |
| Mind Wick Ltd | Information & communication | 2026 |
| Mindforge Nexus Ltd | Wholesale & retail | 2026 |
| Mindfulstep C.I.C. | Health & social care | 2025 |
| Mindscale Systems Limited | Professional & scientific | 2025 |
| Mindwise Ltd | Health & social care | 2010 |
| Ming YU Ltd | Hospitality | 2023 |
| Minh Ltd | Financial services | 2022 |
| Mini Marvels (Sussex) Limited | Education | 2023 |
| Ministry of INK Ltd | Wholesale & retail | 2010 |
| Minorworks Design Limited | Professional & scientific | 2008 |
| Mint Investment Properties Ltd | Construction | 2014 |
| Mint Space Developments Ltd | Construction | 2024 |
| Mint Space Flooring Ltd | Construction | 2025 |
| Mint Space Lettings Ltd | Real estate | 2025 |
| Mintrooms Ltd | Administrative & support | 2015 |
| Miramar House (Eastbourne) Limited | Households | 2003 |
| Mirasol Residents Association Limited | Households | 1970 |
| Miriam Care Limited | Health & social care | 2024 |
| Miriams Maids UK Ltd | Administrative & support | 2017 |
| Mirox Property Limited | Financial services | 2015 |
| Miru Studios Ltd | Professional & scientific | 2024 |
| Mirusproperty Limited | Construction | 2005 |
| Mishortstays Accommodation Limited | Real estate | 2023 |
| Misty Lane Vape Ltd | Wholesale & retail | 2025 |
| Mistywell Limited | Real estate | 1980 |
| MIT Shakes Limited | Hospitality | 2024 |
| Miwasi Ltd | Real estate | 2024 |
| MIX & Glow Superfoods Ltd | Wholesale & retail | 2025 |
| MJ & C Properties Limited | Real estate | 2024 |
| MJ Hampson Financial Services Ltd | Financial services | 2013 |
| MJ Revenue Limited | Health & social care | 2018 |
| Mj-A Fire Safety Consultant Ltd | Professional & scientific | 2023 |
| MJA FD Services Limited | Financial services | 2014 |
| MJB Studio Limited | Information & communication | 2007 |
| MJJ Services Limited | Administrative & support | 2008 |
| MJN Dental Limited | Health & social care | 2021 |
| MJN Design Solutions Limited | Professional & scientific | 2010 |
| MJS Cost Management Ltd | Construction | 2019 |
| MJW Jointing Solutions Limited | Construction | 2024 |
| MK & MK Decorations Ltd | Construction | 2026 |
| MK Barber Ltd | Other services | 2018 |
| MK Publishing Limited | Information & communication | 2023 |
| MK Smiles Partnership Limited | Financial services | 2022 |
| MKB Investments Limited | Real estate | 2015 |
| Mkja Holdings Ltd | Financial services | 2021 |
| Mkja Investments Ltd | Financial services | 2022 |
| Mkkah Limited | Financial services | 2023 |
| Mksa Consultancy Limited | Professional & scientific | 2012 |
| MLH Ventures Limited | Real estate | 2022 |
| MM Digital Services Ltd | Wholesale & retail | 2026 |
| MM Singh Ltd | Hospitality | 2019 |
| MM47 Limited | Real estate | 2015 |
| MMB Caines Consulting Limited | Administrative & support | 2015 |
| MMC Healthcare Ltd | Health & social care | 2025 |
| Mmec Electrical Ltd | Construction | 2024 |
| Moatview Limited | Real estate | 2016 |
| Moba England Limited | Extraterritorial | 2014 |
| Mobile Plus Eastbourne Limited | Manufacturing | 2024 |
| Mobility Plus Transport Ltd | Transport & logistics | 2014 |
| Modepoint Limited | Arts & recreation | 2001 |
| Modestum Ltd | Information & communication | 2021 |
| Modesty Designs Limited | Wholesale & retail | 2013 |
| Modify Media Ltd | Information & communication | 2025 |
| Mokara Limited | Professional & scientific | 1998 |
| Molar Creations Limited | Health & social care | 2017 |
| Mole Hill Estates Ltd | Real estate | 2018 |
| Molekul Limited | Health & social care | 2021 |
| Molior Limited | Extraterritorial | 2023 |
| Molior London Limited | Administrative & support | 2008 |
| Momentum Selection Limited | Professional & scientific | 2015 |
| Monarch House Management Company Limited | Households | 1988 |
| Monarch Oak Limited | Construction | 2011 |