| Mango AI Limited | Information & communication | 2021 |
| Mansion Management Ltd | Real estate | 2007 |
| Maplecroft Estates Limited | Real estate | 2021 |
| Marden Roofing Limited | Construction | 2003 |
| Mark J Pursey & SON Limited | Manufacturing | 2025 |
| Mark Selway Carpentry and Restoration Limited | Construction | 2015 |
| Mark-It Square Ltd | Real estate | 2021 |
| Marketing Xperts Limited | Other services | 2008 |
| Marques Consulting Ltd | Administrative & support | 2022 |
| Marsey Travel Ltd | Administrative & support | 2025 |
| Martin Alexander Painting and Decorating Ltd | Construction | 2012 |
| Mash Haven Ltd | Real estate | 2024 |
| Mastercharge Ltd | Manufacturing | 2018 |
| Matt FOX Photography Ltd | Professional & scientific | 2022 |
| Mature Mixers Limited | Hospitality | 2024 |
| Maurice Hubert Associates Ltd | Professional & scientific | 2011 |
| Mayfair Fidelio Automobiles Limited | Wholesale & retail | 2023 |
| Mayfair Fidelio Projects Ltd | Construction | 2026 |
| MB Locksmiths Ltd | Administrative & support | 2018 |
| MBC Associates Ltd. | Professional & scientific | 2006 |
| Mccall Collective Limited | Professional & scientific | 2026 |
| Mccombies.Co Ltd | Information & communication | 2014 |
| Mckenzie Wealth Management Ltd | Financial services | 2010 |
| Mdrv Property Ltd | Real estate | 2020 |
| Meads of Melksham Ltd | Wholesale & retail | 2018 |
| Mejbs Ltd | Hospitality | 2025 |
| Melissa Jongen Consultancy Ltd | Professional & scientific | 2024 |
| Melksham Amateur Boxing Club CIC | Arts & recreation | 2025 |
| Melksham Antiques Ltd | Wholesale & retail | 2012 |
| Melksham Arcade House Clearance & Home Decor Ltd | Wholesale & retail | 2022 |
| Melksham B Ltd | Other services | 2023 |
| Melksham Card & News Centre Limited | Wholesale & retail | 2001 |
| Melksham Companionship Group CIC | Professional & scientific | 2022 |
| Melksham Food and River Festival Limited | Arts & recreation | 2018 |
| Melksham Groundcare Machinery Ltd | Wholesale & retail | 2015 |
| Melksham Minimix Ltd | Transport & logistics | 2018 |
| Melksham Mobile Home Park Limited | Real estate | 2021 |
| Melksham Motor Spares Limited | Wholesale & retail | 1978 |
| Melksham Music Festival Limited | Arts & recreation | 2012 |
| Melksham Pizza Limited | Hospitality | 2023 |
| Melksham Rugby Football Club Limited | Arts & recreation | 2011 |
| Melksham Scaffolding Ltd | Construction | 2014 |
| Melksham Tasty BUN Limited | Hospitality | 2025 |
| Melksham Tourist Information Centre Ltd | Administrative & support | 2006 |
| Melwood Automotive Ltd | Wholesale & retail | 2011 |
| Memorial Print Ltd | Manufacturing | 2024 |
| Meraki Life Limited | Wholesale & retail | 2015 |
| Mercury Motorcycle Training Ltd | Education | 2021 |
| Merlin Security Ltd | Administrative & support | 2019 |
| MG Replacement Windows Ltd | Construction | 2014 |
| MGS Plastering Ltd | Construction | 2024 |
| Microbz Ltd | Manufacturing | 2010 |
| Milk Town Brewing Company Ltd | Manufacturing | 2024 |
| Mimi TEE Ltd | Wholesale & retail | 2020 |
| Miramar Assets Limited | Real estate | 2026 |
| Miramar Assets Two Limited | Other services | 2026 |
| Miss Mama Wigs Limited | Manufacturing | 2022 |
| Mizen Plasterers Limited | Construction | 2007 |
| MK Brand Upholstery Ltd | Manufacturing | 2025 |
| ML Data Cabling Ltd | Information & communication | 2025 |
| Mo's Communications Services Ltd | Professional & scientific | 2012 |
| Moda Living Spaces Ltd | Real estate | 2025 |
| Moja Khabar Limited | Hospitality | 2017 |
| Mojerad.Io Ltd | Information & communication | 2025 |
| Monty and Moose Limited | Information & communication | 2024 |
| MOO Consultants Limited | Professional & scientific | 2011 |
| Moor Park Associates Ltd | Professional & scientific | 2023 |
| Moorland Convenience Stores Ltd | Wholesale & retail | 2024 |
| Moto Smart Limited | Wholesale & retail | 2020 |
| Mowe & Co Ltd | Administrative & support | 2015 |
| MPD Pumps Ltd | Administrative & support | 2008 |
| MR Sparkles Melksham Limited | Administrative & support | 2014 |
| MRH Air Conditioning Ltd | Construction | 2016 |
| MS Brickwork (SW) Ltd | Construction | 2016 |
| MS Developments (SW) Limited | Construction | 2021 |
| MSA IT Support Limited | Information & communication | 2012 |
| Msec Security Ltd | Administrative & support | 2025 |
| MTD Building & Landscaping Ltd | Construction | 2025 |
| Mtfc Performance Hub Ltd | Arts & recreation | 2025 |
| Multi Pump Distribution Limited | Manufacturing | 2003 |
| Multibuild Bricklaying Limited | Construction | 2000 |
| Multibuild Properties Limited | Administrative & support | 2005 |
| MV Electrics Ltd | Construction | 2021 |
| My Pet PAL Ltd | Wholesale & retail | 2025 |
| Myah Technology Limited | Information & communication | 2018 |
| N I Smith Transport Melksham Limited | Transport & logistics | 2014 |
| N&D Optics Ltd | Construction | 2023 |
| Nace Educational Services Limited | Education | 2013 |
| Naked Skin Aesthetics Limited | Other services | 2024 |
| Nartana Retail Ltd | Wholesale & retail | 2025 |
| Nash Bustorff-Silva Ltd | Professional & scientific | 2015 |
| Naturally Social Ltd | Professional & scientific | 2019 |
| Neon Cricket Limited | Wholesale & retail | 2017 |
| Neptune Aquatics (LW) Ltd | Arts & recreation | 2022 |
| Neptune Aquatics (Social Enterprise) Ltd | Arts & recreation | 2013 |
| Neston Park Joinery Ltd | Manufacturing | 2014 |
| Netsketch Limited | Information & communication | 2011 |
| New Level Estates Ltd | Administrative & support | 2003 |
| New Level Health Limited | Professional & scientific | 2010 |
| New Level Safety Limited | Professional & scientific | 2003 |