| March Self Store Ltd | Transport & logistics | 2013 |
| March Shop Ltd | Wholesale & retail | 2024 |
| March Star Cuts Limited | Other services | 2026 |
| March Tandoori & Desserts Ltd | Hospitality | 2026 |
| March Tandoori Ltd | Hospitality | 2024 |
| March Town FC Estover CIC | Arts & recreation | 2015 |
| Marginchain Residents Management Limited | Households | 1988 |
| Mario Smart Ltd | Construction | 2025 |
| Marlowe & Hare Ltd | Construction | 2026 |
| Mars Triangle Limited | Information & communication | 2025 |
| Marsh Site Services Ltd | Construction | 2024 |
| Martin Hardy Associates Limited | Administrative & support | 2012 |
| Martodoc Ltd | Information & communication | 2025 |
| Mason Homes (March) Limited | Construction | 1990 |
| Master Football Academy (UK) Limited | Extraterritorial | 1997 |
| Masters Logistical Services Limited | Transport & logistics | 2006 |
| Matt E Clinical Coder U.K Ltd | Administrative & support | 2025 |
| Maxi Kuczek Ltd | Transport & logistics | 2014 |
| MB Fabrication and Welding Ltd | Manufacturing | 2024 |
| MBF Bathrooms Ltd | Construction | 2026 |
| Mcgarvie Developments Limited | Construction | 2022 |
| MD Pearce Developments Ltd | Construction | 2021 |
| MDJ Concrete Ltd | Wholesale & retail | 2025 |
| MDJ Real Estates Ltd | Manufacturing | 2011 |
| Mega VAC UK Ltd | Financial services | 2021 |
| MEN of March Ltd | Hospitality | 2025 |
| Merchford Plumbing and Heating Limited | Construction | 2009 |
| MG (Cambs) Ltd | Hospitality | 2023 |
| MG Security Consulants Ltd | Administrative & support | 2024 |
| Mhak Holdings Ltd | Financial services | 2025 |
| Microns (P.E.) Holdings Limited | Financial services | 2025 |
| Microns (P.E.) Limited | Manufacturing | 2011 |
| Mill Cottage Plumbing & Heating Ltd | Construction | 2019 |
| Mill Hill Lane Infrastructure Ltd | Households | 2026 |
| Millennium K9 Services Ltd | Administrative & support | 2021 |
| Millfield Developments (March) Limited | Construction | 2008 |
| Millsavvy Ltd | Professional & scientific | 2024 |
| Milmoore Ltd | Extraterritorial | 2011 |
| Mitchell Training Limited | Administrative & support | 2023 |
| MJS Civils (March) Ltd. | Construction | 2014 |
| MKD Recruit Limited | Transport & logistics | 2014 |
| Modern Cambridgeshire Developments Ltd | Construction | 2025 |
| Moneywise Accounting Ltd | Professional & scientific | 2011 |
| Monkstone House Limited | Construction | 2025 |
| Moonlight Grill (March) Ltd | Hospitality | 2019 |
| Moore's Safe Suction Ltd | Construction | 2025 |
| Morton Buller Property Limited | Real estate | 2008 |
| Morton Consulting Holdings Limited | Professional & scientific | 2005 |
| Morton Technical Services Limited | Construction | 2023 |
| Moto-Mate Ltd | Manufacturing | 2020 |
| Mova Homes Ltd | Extraterritorial | 2021 |
| Move IT Quickly Ltd | Transport & logistics | 2019 |
| MP GAS Certificate & Servicing Limited | Construction | 2021 |
| MP Plumbing & Heating Limited | Construction | 2018 |
| MPV (Contractors) Ltd | Energy | 2018 |
| MR Green Shop Ltd | Wholesale & retail | 2025 |
| MR Home Improvements Cambs Ltd | Construction | 2025 |
| MS Management Consultancy Ltd | Professional & scientific | 2010 |
| MSG Grab Hire Ltd | Transport & logistics | 2021 |
| MSN Retail (Benwick) Ltd | Wholesale & retail | 2024 |
| Mulberry (March) Ltd | Other services | 2019 |
| Mundell Engineering Limited | Manufacturing | 2004 |
| Mykonos and Co Ltd | Hospitality | 2024 |
| N G I Utilities Ltd | Professional & scientific | 2025 |
| N J Marketing Limited | Manufacturing | 1989 |
| N W Brickwork Limited | Construction | 2017 |
| Nama Solutions Ltd | Wholesale & retail | 2023 |
| Nanomolar Limited | Information & communication | 2021 |
| Ncmf Ltd | Transport & logistics | 2018 |
| Neil Cawthorn Accident Repairs Limited | Wholesale & retail | 2013 |
| Nene Interiors Ltd | Construction | 2026 |
| NEO Gaminguk Ltd | Wholesale & retail | 2025 |
| Neural Blue Ltd | Information & communication | 2007 |
| New Leaf Foods Ltd | Professional & scientific | 2021 |
| Newflow Utilities Ltd | Construction | 2026 |
| Newgate Developments (Cambs) Limited | Construction | 2004 |
| Newman & Hayes Brickwork Contractors Ltd | Construction | 2024 |
| Newton Utilities Limited | Construction | 2023 |
| Next Level Property Services Ltd | Real estate | 2022 |
| Nextmile Motors Ltd | Wholesale & retail | 2021 |
| Nichola Jones Limited | Real estate | 2011 |
| Nicola S Matthews Ltd | Information & communication | 2022 |
| Nineteen Hundred Aviation Ltd | Professional & scientific | 2009 |
| NJ FOX Plumbing & Heating Services Limited | Construction | 2020 |
| NKT Builds Ltd | Construction | 2024 |
| Nor-Cambs Homes & Developments Ltd | Construction | 2007 |
| Norfolk and Cambridgeshire Rural Retreats Ltd | Hospitality | 2024 |
| Norfolk Prestige Ltd | Construction | 2023 |
| Northampton House RTM Company Limited | Households | 2009 |
| Northern Retail Solutions Ltd | Construction | 2019 |
| Nova Vita Solutions Limited | Professional & scientific | 2017 |
| Novus Properties Cambridge Limited | Construction | 2024 |
| NP Carpentry Services Limited | Construction | 2018 |
| Nurtured Therapy Ltd | Health & social care | 2024 |
| NXT Level Communications Ltd | Information & communication | 2025 |
| Oakwood (Wimblington) Management Company Ltd | Households | 2023 |
| Ocius IT Ltd | Administrative & support | 2016 |
| Ogden Motor Engineers Limited | Wholesale & retail | 2011 |
| Omnis Medical Ltd | Manufacturing | 2024 |
| One Total Equipment Solution Limited | Manufacturing | 2020 |