| Mark Burrell Painting & Decorating Limited | Construction | 2025 |
| Mark Goodhall Design Limited | Construction | 2014 |
| Mark Templer & Company Limited | Real estate | 2002 |
| Marshfield Park Management Company (Downend) Limited | Households | 1973 |
| Martial Fitness (SW) Ltd | Arts & recreation | 2025 |
| Marvel Taverns & Inns Ltd | Hospitality | 2025 |
| Mass Beauty Products Ltd | Wholesale & retail | 2015 |
| Masterloader Limited | Professional & scientific | 1995 |
| Masters Pubs Limited | Hospitality | 2025 |
| Matric Accommodation Limited | Hospitality | 2021 |
| Matric Asset Management Limited | Real estate | 2021 |
| Matric Developments (Karpaignton) Limited | Real estate | 2021 |
| Matric Developments (Roadwater) Limited | Real estate | 2023 |
| Matric Developments (Taunton) Limited | Real estate | 2023 |
| Matric Probate Acquisitions Limited | Real estate | 2021 |
| Matthew Charles Harvey Jones Ltd | Extraterritorial | 2024 |
| Matthew Freeman Limited | Health & social care | 2026 |
| Matthew Olivers Ltd | Administrative & support | 2019 |
| MAX3DPRINTS Limited | Wholesale & retail | 2026 |
| Maxim Financial Planning Limited | Financial services | 2014 |
| MB Construction Bristol Limited | Construction | 2017 |
| MBS Land and New Homes Ltd | Professional & scientific | 2018 |
| MCB Enterprises Limited | Information & communication | 2023 |
| Mcmanus Williams KGG Limited | Professional & scientific | 2018 |
| Mcmanus Williams Limited | Professional & scientific | 2010 |
| Meade Builders Limited | Construction | 2007 |
| Meadow Farm (Emersons Green) Management Company Limited | Households | 2000 |
| MED Properties Limited | Real estate | 2004 |
| Medacrii Associates Limited | Professional & scientific | 2021 |
| Medcare Rehab Limited | Health & social care | 2006 |
| Medcare Treatment Services Limited | Professional & scientific | 2003 |
| Medlaw Assist Ltd | Administrative & support | 2008 |
| MEE Compliance Consultancy Limited | Professional & scientific | 2008 |
| Melbourne House Management Co Limited | Households | 2011 |
| Melrose Group of Associates Ltd | Professional & scientific | 2025 |
| Mendip Accounting Solutions Limited | Professional & scientific | 2007 |
| Mendip HR & Payroll Solutions Limited | Administrative & support | 2020 |
| Method Independent Consulting Limited | Professional & scientific | 2024 |
| MG Broker Ltd | Financial services | 2021 |
| MG Consultancy London Ltd | Information & communication | 2014 |
| MGS SW Group Ltd | Administrative & support | 2024 |
| Middleton Homes Limited | Construction | 1986 |
| Mike Ball Financial Services Limited | Financial services | 2016 |
| Mike Bishop Consulting Limited | Professional & scientific | 2020 |
| Mike Goodfield Limited | Construction | 2020 |
| Mike Mchugh Ltd | Wholesale & retail | 2024 |
| Mike Smith IFA Ltd. | Financial services | 2012 |
| Millers Court Management Company Limited | Households | 2003 |
| Mimi's Preloved Ltd | Wholesale & retail | 2018 |
| MJS Carpentry Limited | Construction | 2017 |
| Mlassociates Ltd | Administrative & support | 2023 |
| Mohunky Limited | Information & communication | 2019 |
| Moneymates UK Limited | Financial services | 2022 |
| Moor Park Court Limited | Households | 2019 |
| Moorcroft Accountancy & Taxation Limited | Professional & scientific | 2011 |
| Moorcroft Bureau Services Limited | Professional & scientific | 2015 |
| Moorcroft Estate Management Limited | Real estate | 2022 |
| Moores Motorcars Limited | Wholesale & retail | 2013 |
| Moorfields (Locking Castle) Management Company Limited | Households | 2004 |
| Morpheus Intensivists Limited | Health & social care | 2023 |
| Morris Nicholas 0962 Limited | Transport & logistics | 2014 |
| Moteur Incentive (UK) Limited | Wholesale & retail | 2011 |
| Motion Gate Ltd | Manufacturing | 2015 |
| Motorcycle Roadcraft Limited | Education | 2018 |
| MR Gillman Tuition CIC | Education | 2025 |
| MR PUB Ltd | Hospitality | 2023 |
| MRC Accountancy (SW) Ltd | Professional & scientific | 2023 |
| MRK Maintenance Ltd | Administrative & support | 2018 |
| MRW Couriers Limited | Transport & logistics | 2024 |
| Msgboxx Limited | Information & communication | 2021 |
| Mulberry House Holiday Cottages Ltd | Real estate | 2017 |
| Mullholland Park (Burnham) Management Company Limited | Households | 2008 |
| Murray Brown Consultancy Limited | Professional & scientific | 2017 |
| Murrays of Clevedon Limited | Wholesale & retail | 2006 |
| MWS Commercial Services LLP | | 2018 |
| Mylightning.Info Limited | Information & communication | 2021 |
| Myproject.Builders Ltd | Construction | 2021 |
| N.T. Voisey & Company Limited | Construction | 1957 |
| N.W Carpentry & Build Ltd | Manufacturing | 2024 |
| Nactarome Limited | Manufacturing | 2002 |
| Nactarome UK Limited | Financial services | 2020 |
| Nanona Limited | Hospitality | 2013 |
| NAO Property Limited | Real estate | 2024 |
| Natural Habitat Designs Limited | Extraterritorial | 2020 |
| Natural Motion Chiropractic Ltd | Health & social care | 2009 |
| Naylor Inspection Services Ltd | Other services | 2006 |
| ND Medical Communications Limited | Professional & scientific | 2020 |
| NDJ Hospitality Limited | Hospitality | 2025 |
| Neads Properties Limited | Households | 2025 |
| Nejma Management Ltd | Professional & scientific | 2023 |
| Network Britannia Limited | Construction | 2008 |
| Network Britannia Windows Limited | Wholesale & retail | 2011 |
| New Park House Management Limited | Households | 1965 |
| New Space Building Services Ltd | Construction | 2019 |
| New Wave Landscaping Ltd | Administrative & support | 2023 |
| Newminster House Bristol Limited | Real estate | 2022 |
| Newsham Hanson Accountants Limited | Professional & scientific | 2019 |
| Newsky Consulting Ltd | Professional & scientific | 2025 |
| Newtonian Properties Ltd | Construction | 2015 |
| NGM Surveys Ltd | Construction | 2025 |