| Meridian Leisure & Entertainment Ltd | Hospitality | 2013 |
| Mernaz Limited | Financial services | 2022 |
| Merrill Developments Ltd | Construction | 2024 |
| Meta Unity Ltd | Professional & scientific | 2024 |
| Metaphase Demolition Limited | Wholesale & retail | 2004 |
| Meteor Minerals (UK) Ltd | Professional & scientific | 2022 |
| Mews at Querns Limited | Households | 2008 |
| Meysey Construction Limited | Construction | 2011 |
| Mezze Garden Ltd | Hospitality | 2025 |
| MG Food Style Limited | Hospitality | 2024 |
| MGI Future Limited | Financial services | 2015 |
| MH Cripps Ltd | Hospitality | 2018 |
| MHT (One) Limited | Professional & scientific | 2006 |
| Mibex Consultants Ltd | Professional & scientific | 2024 |
| Michael Hart & SON Limited | Wholesale & retail | 2003 |
| Michael Rixon Building & Roofing Ltd | Construction | 2017 |
| Michaelmas Farming Limited | Agriculture & fishing | 1996 |
| Michelle Cyril Ltd | Health & social care | 2025 |
| Micro-Vision Fire & Security Ltd | Administrative & support | 2000 |
| Micromkt Limited | Information & communication | 2016 |
| Middle Lypiatt Glamping Limited | Hospitality | 2026 |
| Middleton Bray Upholstery Ltd | Other services | 2015 |
| Mike Garlick Ltd | Professional & scientific | 2016 |
| Mike Grosscurth (Surveys) Limited | Professional & scientific | 2010 |
| Millbourne Ltd | Financial services | 2024 |
| Milner Energy Trading Ltd | Wholesale & retail | 2018 |
| Mimaroo Labs Ltd | Information & communication | 2023 |
| Mimm.Properties Ltd | Real estate | 2022 |
| Minerva Computing Limited | Information & communication | 1999 |
| Minety Playing Fields Association Limited | Hospitality | 2023 |
| Minley Management Ltd | Real estate | 2014 |
| Mint Interactive Solutions Ltd | Information & communication | 2021 |
| Miriampam Ltd | Health & social care | 2022 |
| Miroir Ltd | Information & communication | 2026 |
| Mitchell Griffin Wealth Management Limited | Financial services | 2005 |
| Mizon Builders Limited | Construction | 2007 |
| MJ Hudson Investments I LP | | 2017 |
| MJP Commercial Services Limited | Professional & scientific | 2016 |
| MJS Solitaire Limited | Professional & scientific | 2022 |
| MKT LAB Limited | Information & communication | 2023 |
| ML Glamping LLP | | 2022 |
| Mler Ltd | Financial services | 2022 |
| MMF Bristol Limited | Wholesale & retail | 2019 |
| Mmmultiply Ltd | Professional & scientific | 2011 |
| MMO Logistics Limited | Information & communication | 2006 |
| Mobitech Cirencester Ltd | Wholesale & retail | 2017 |
| Modulus Estates Ltd | Construction | 2024 |
| Modulus Events Ltd | Construction | 2021 |
| Moke Fine Wines Limited | Wholesale & retail | 2010 |
| Monarch Electrical Ltd | Construction | 2022 |
| Monfa Consulting Limited | Administrative & support | 2014 |
| Monk Building Contractors Ltd | Construction | 2010 |
| Monsterwrapsuk Limited | Wholesale & retail | 2022 |
| Monti Investments Ltd | Real estate | 2025 |
| Montpellier Spa Road (Management Company) Limited | Households | 1996 |
| Montsam Holdings Limited | Administrative & support | 2026 |
| Montsam Properties Limited | Real estate | 2026 |
| Mooms Property Ltd | Real estate | 2020 |
| Moose-Beast Developments Ltd | Administrative & support | 2010 |
| Moose-Beast Software Ltd | Information & communication | 2011 |
| Moran Masonry Limited | Construction | 2026 |
| Moreleaze Marketing Limited | Administrative & support | 2004 |
| Moreton in Marsh DRY Cleaning Company LLP | | 2003 |
| Morgan and Cavendish Developments Ltd | Construction | 2015 |
| Morgan's Walk Management Limited | Households | 1983 |
| Moriel Healthcare Ltd | Public administration | 2023 |
| Morris Ipsen Ltd | Information & communication | 2018 |
| Morse Roofing and Scaffolding Ltd | Construction | 2016 |
| Morse Scaffolding Limited | Construction | 2019 |
| Mortegrove Limited | Wholesale & retail | 1991 |
| Mortgage Wise Ltd. | Professional & scientific | 2014 |
| Mortgages With Sally Ltd | Financial services | 2021 |
| Mosaic IT Training Ltd | Information & communication | 2013 |
| Mosaique Creative & Marketing Limited | Professional & scientific | 2012 |
| Mosaique Group Limited | Professional & scientific | 2023 |
| Mosii-England Limited | Professional & scientific | 2020 |
| Mosman Estates Ltd | Construction | 2020 |
| Mothers of Invention LLP | | 2011 |
| Moths Studio Ltd | Wholesale & retail | 2025 |
| Moto House Service Ltd. | Wholesale & retail | 2006 |
| Motortech (Cirencester) Limited | Wholesale & retail | 2007 |
| Moualed ENT Services Ltd | Health & social care | 2022 |
| Mount Seenai Limited | Wholesale & retail | 2020 |
| MPH Resources Limited | Professional & scientific | 2013 |
| MPP Media Limited | Information & communication | 2014 |
| MRA Services Ltd | Wholesale & retail | 2025 |
| MT Bookkeeping Services Limited | Professional & scientific | 2004 |
| Mulberry Partners Limited | Real estate | 2006 |
| Mullfern Civil Engineering Limited | Wholesale & retail | 2004 |
| Mumbles 2 Ltd | Construction | 2017 |
| Mumbles 8 Limited | Real estate | 2021 |
| Mumbles Group Limited | Construction | 2008 |
| Mumbles Investment Management Limited | Construction | 2014 |
| Mumpreneur Ltd | Information & communication | 2008 |
| Mumpreneurs Ltd | Education | 2009 |
| Munchaway Catering Ltd | Hospitality | 2024 |
| Muntons Traditional Plant Supports Ltd | Wholesale & retail | 2010 |
| Murphys Equestrian Ltd | Wholesale & retail | 2023 |
| Mushroom Enterprises Ltd | Other services | 2022 |
| Music Theatre Project Limited | Extraterritorial | 2016 |