| Marine Glory Limited | Administrative & support | 2025 |
| Mariners View Management Company Limited | Households | 2003 |
| Maritime Costs Consultants Ltd | Administrative & support | 2008 |
| Maritime Investments (Kent) Limited | Real estate | 2019 |
| Marius Team Painting, Plastering, Tape&Jointing Limited | Construction | 2013 |
| Mark Boyle Estate Agents Ltd | Real estate | 2025 |
| Mark Durant Cleaning LLP | | 2009 |
| Mark King Property & Building Services Ltd | Construction | 2014 |
| Mark Turner Cardiology Limited | Health & social care | 2010 |
| Mark's Couture and Alterations Ltd | Manufacturing | 2019 |
| Marketing That Matters Ltd | Professional & scientific | 2019 |
| Markides Ltd | Professional & scientific | 2024 |
| Markitech Ltd | Information & communication | 2024 |
| Markko Limited | Wholesale & retail | 2021 |
| Markor Ltd | Administrative & support | 2025 |
| Marksman Services Ltd | Other services | 2023 |
| Markstone Masonry & Conservation Ltd | Manufacturing | 2024 |
| Marlborough RTM Company Limited | Households | 2009 |
| Marle Thread Company Limited | Extraterritorial | 2016 |
| Marof Performance Ltd | Wholesale & retail | 2025 |
| Marshall Strategic Ventures Limited | Financial services | 2026 |
| Marshall Synergy Solutions (Holdings) Ltd | Financial services | 2024 |
| Marshall Synergy Solutions Ltd | Professional & scientific | 2024 |
| Marshalls Fire Protection Ltd | Public administration | 2019 |
| Marshalls Global Protection Ltd | Administrative & support | 2022 |
| Martial Arts Krav Maga Academy Kids Limited | Arts & recreation | 2017 |
| Martin Tolhurst Partnership LLP | | 2004 |
| Martyn Colbeck Limited | Information & communication | 2011 |
| Martyn Hall Limited | Financial services | 2010 |
| Mashaq Ltd | Real estate | 2023 |
| Mashinge Sales Ltd | Wholesale & retail | 2025 |
| Masque Clothing Ltd | Wholesale & retail | 2023 |
| Master Chef Consultancy Limited | Wholesale & retail | 2020 |
| Masters Chippy Ltd | Hospitality | 2025 |
| Mastersealants Ltd | Construction | 2023 |
| Mastertech Poole Limited | Wholesale & retail | 2012 |
| Mateer Melts Ltd | Other services | 2026 |
| Mathiya Limited | Professional & scientific | 2022 |
| Matilde’S London Limited | Hospitality | 2024 |
| MATTEO2017 Limited | Transport & logistics | 2017 |
| Mattimia Ltd | Manufacturing | 2023 |
| Matts Hill Development Limited | Construction | 2022 |
| Maureen's Properties Limited | Real estate | 2025 |
| MAX Metal Co., Ltd. | Manufacturing | 2022 |
| Maxwell Marketing Ltd | Construction | 2025 |
| Maya and Andy Clothing Ltd | Manufacturing | 2018 |
| Mayfair Boutique Limited | Manufacturing | 2023 |
| Mayfair Developers Limited | Construction | 2010 |
| Mayjo Healthcare Limited | Other services | 2022 |
| Mayo-Bedford Enterprises Limited | Extraterritorial | 2023 |
| Mayside Gardens Limited | Administrative & support | 2017 |
| Maz's Catering Limited | Hospitality | 2018 |
| MB Trusted Properties Limited | Real estate | 2022 |
| MBA Motors Dorset Ltd | Wholesale & retail | 2025 |
| MBG Transport 91 Ltd | Construction | 2026 |
| MBR Estates Ltd | Real estate | 2025 |
| MC Hammond Property Ltd | Real estate | 2017 |
| MC Modelmaking Ltd | Professional & scientific | 2000 |
| MC Property Maintenance (Kent) Limited | Construction | 2026 |
| Mccormack Media Ltd | Professional & scientific | 2026 |
| Mccue Productions Ltd | Information & communication | 2018 |
| Mcculloch Furniture Ltd | Manufacturing | 2010 |
| Mcglynn Limited | Wholesale & retail | 2016 |
| Mcgrath & Wells Ltd | Hospitality | 2025 |
| Mcilheron's Development Group Limited | Real estate | 2023 |
| Mcmanus External Solutions Ltd | Information & communication | 2020 |
| Mcmanus Flat Roof Finishing Ltd | Construction | 2013 |
| Mcmanus Property Development Ltd | Construction | 2019 |
| MCP (Kent) Limited | Real estate | 2005 |
| MCR (SE) Consultancy Ltd | Professional & scientific | 2018 |
| Mctaggart Farley Ltd | Professional & scientific | 2014 |
| Mcvidale Ltd | Administrative & support | 2025 |
| Mcvidale Properties UK Ltd | Households | 2024 |
| Mcwilliams Electrical Ltd | Construction | 2022 |
| MD Auction-Sell Ltd | Wholesale & retail | 2021 |
| MD Building Construct Ltd | Construction | 2018 |
| MD Thompson Ltd | Hospitality | 2026 |
| MDG Management Ltd | Professional & scientific | 2017 |
| MDH Commercial and Residential Limited | Real estate | 2024 |
| MDM Publishing Limited | Information & communication | 1999 |
| Mdmar Ltd | Transport & logistics | 2016 |
| MDO Heating and Plumbing Ltd | Construction | 2019 |
| ME Diabetes Care Ltd | Health & social care | 2022 |
| ME Legal Ltd | Professional & scientific | 2019 |
| Meadowsweet Investments Limited | Financial services | 2025 |
| Meadway Enterprise Ltd | Hospitality | 2018 |
| Mecurator Limited | Arts & recreation | 2020 |
| Medfina Ltd | Health & social care | 2025 |
| Medicare International Limited | Professional & scientific | 2022 |
| Medicare Southeast Ltd | Public administration | 2024 |
| Medsafe Solutions Ltd | Education | 2026 |
| Medskill Ltd | Professional & scientific | 2025 |
| Medway & Kent Homes Ltd | Real estate | 2023 |
| Medway 2015 Ltd | Construction | 2018 |
| Medway Accommodation Limited | Hospitality | 2000 |
| Medway Active Alliance Ltd | Wholesale & retail | 2024 |
| Medway and Maidstone Blinds Limited | Manufacturing | 2021 |
| Medway and Swale Local Care CIC | Health & social care | 2021 |
| Medway Anglican Schools Trust | Education | 2015 |
| Medway AV Ltd | Information & communication | 2022 |