| Mccullochs Limited | Professional & scientific | 1990 |
| MCD Manufacturing & Logistics Ltd | Administrative & support | 2019 |
| MCG Law Limited | Professional & scientific | 2021 |
| Mcguffie Consultants Ltd | Professional & scientific | 1983 |
| Mcguire Mitchell Limited | Professional & scientific | 2017 |
| MCH (Bath) Limited | Financial services | 2008 |
| Mcintosh Taylor Ltd | Professional & scientific | 2003 |
| Mckenzie Cardiology Services Limited | Health & social care | 2023 |
| Mcmenemy Stays Limited | Hospitality | 2024 |
| Mcmullen Commercial Limited | Real estate | 2005 |
| Mcmurray & Co Event Catering Limited | Hospitality | 2018 |
| Mcneil Commercial Limited | Professional & scientific | 2009 |
| MCO Limited | Real estate | 2022 |
| Mcwisker Ltd | Information & communication | 2024 |
| MDC Solutions Ltd | Professional & scientific | 2023 |
| ME Business Transformation Ltd | Professional & scientific | 2018 |
| ME Coach House Ltd | Real estate | 2026 |
| MEA Fabula Ltd | Professional & scientific | 2013 |
| Meade Yard Surveyors Ltd | Professional & scientific | 2024 |
| Meadgate Cafe Limited | Hospitality | 2022 |
| Meadgate Recovery Services Limited | Construction | 1988 |
| Meadow Lane Lettings LLP | | 2015 |
| Meadow Learning CIC | Education | 2022 |
| Meadow Park Management Ltd | Other services | 2018 |
| Meadows Financial Services Ltd | Professional & scientific | 2025 |
| Meaning & Mechanism Limited | Information & communication | 2026 |
| Mecanile Services Ltd | Administrative & support | 2005 |
| Mechanical Electrical Engineering Services Limited | Construction | 2006 |
| Mechano Medicine Limited | Professional & scientific | 2015 |
| Medi Local Ltd | Other services | 2026 |
| Media Bath Limited | Information & communication | 2015 |
| Media House RTM Company Limited | Households | 2021 |
| Media Space Advertising Limited | Professional & scientific | 2017 |
| Mediaclash Holdings Limited | Financial services | 2006 |
| Mediaclash Limited | Information & communication | 2002 |
| Mediation in the Workplace Ltd | Professional & scientific | 2009 |
| Medical Specialties of California UK Limited | Manufacturing | 1998 |
| Medical UX Ltd | Professional & scientific | 2019 |
| Medici Estates Ltd | Real estate | 2023 |
| Medit Solutions Limited | Professional & scientific | 2025 |
| Medlar Music Limited | Arts & recreation | 2002 |
| Medlock Enterprises Ltd | Health & social care | 2025 |
| Medskin Limited | Health & social care | 2024 |
| Meeca Limited | Hospitality | 2025 |
| Meet Bath Limited | Hospitality | 2021 |
| Meet Jesus Limited | Manufacturing | 2000 |
| Meet Jesus NOW Limited | Manufacturing | 2022 |
| Meeting Magpie Limited | Professional & scientific | 2018 |
| Megacon Controls Limited | Manufacturing | 1979 |
| Megacon International Limited | Professional & scientific | 2001 |
| Megacon Limited | Extraterritorial | 2024 |
| Megellfinn Financial Planning Limited | Financial services | 2025 |
| MEI Creative Limited | Professional & scientific | 2014 |
| Meica Engineering Ltd | Professional & scientific | 2024 |
| Melapis Ltd | Professional & scientific | 2021 |
| Meldon & Co Ltd | Financial services | 1984 |
| Melford Resolution Limited | Wholesale & retail | 2002 |
| Melksham 1234 Ltd | Professional & scientific | 2019 |
| Melksham Express Transport Limited | Transport & logistics | 2017 |
| Melksham Tackle Company Ltd | Wholesale & retail | 2022 |
| Mellon Udrigle Ltd | Professional & scientific | 2026 |
| Mema Property Limited | Real estate | 2020 |
| Member Digital Ltd | Information & communication | 2012 |
| Membury Building Services Ltd | Construction | 2021 |
| Memorial House Management Company Limited | Hospitality | 2014 |
| Menagerie Products Ltd | Wholesale & retail | 2018 |
| Mendelevium Limited | Professional & scientific | 2020 |
| Mendip Consulting Limited | Professional & scientific | 2012 |
| Mendip Machinery Ltd | Wholesale & retail | 2022 |
| Mendip Springs Limited | Real estate | 2019 |
| Mentioncard Limited | Real estate | 2001 |
| Mentor Training and Simulation (Splutter) Limited | Education | 2020 |
| Mentoring Plus Bath and North East Somerset Ltd | Health & social care | 2005 |
| Menu Gordon Jones Ltd | Hospitality | 2013 |
| Merchant Advisory Ltd | Financial services | 2020 |
| Merchants Garden Management Company Limited | Households | 1983 |
| Mercita Collett Nurse Consultancy Limited | Health & social care | 2012 |
| Mercy in Action | Other services | 2003 |
| Mercy in Action Trading Limited | Wholesale & retail | 2017 |
| Merganser Consulting Ltd | Education | 2007 |
| Meriden House Management Company Limited | Professional & scientific | 1987 |
| Merlin Gallery Ltd. | Wholesale & retail | 2003 |
| Merrion Group Ltd | Construction | 2015 |
| MES Financial Group Limited | Financial services | 2025 |
| MES Financial Services Limited | Financial services | 2017 |
| MES Pension Trustees II Limited | Financial services | 2022 |
| MES Pension Trustees Limited | Financial services | 2022 |
| MET International Limited | Professional & scientific | 2020 |
| Metabolic Solutions Ltd | Professional & scientific | 2022 |
| Metagility Limited | Professional & scientific | 2016 |
| Metallum Commodity Consulting (UK) Ltd | Information & communication | 2016 |
| Methane Exchange Limited | Water & waste | 2015 |
| Method Apps Limited | Information & communication | 2018 |
| Method LAB Ltd | Education | 2026 |
| Meticulous INK Ltd | Manufacturing | 2015 |
| Metrik Space Ltd | Professional & scientific | 2020 |
| Metro 55 Limited | Information & communication | 2004 |
| Meytara Finance Limited | Professional & scientific | 2010 |
| MF Design & Build Ltd | Construction | 2021 |
| MG Construction Management Services Ltd | Professional & scientific | 2018 |