| Marcus Sibley Carpets Limited | Wholesale & retail | 2020 |
| Margarida Serra Ltd | Professional & scientific | 2016 |
| Mario’S Caring Ltd | Health & social care | 2018 |
| Mark J Irving Ltd | Construction | 2024 |
| Mark Stracey Ltd | Professional & scientific | 2016 |
| Market Milloner Ltd | Wholesale & retail | 2025 |
| Market Plaice Fish & Chips Ltd | Hospitality | 2018 |
| Marni Official Limited | Health & social care | 2020 |
| Marshalls Waste Limited | Water & waste | 2025 |
| Martyn Joyce House (Norwich) Limited | Households | 2026 |
| Masala Dhaba Ltd | Hospitality | 2024 |
| Matrix Wiring Limited | Manufacturing | 2006 |
| Matt Hammond Landscaping Ltd | Administrative & support | 2018 |
| Mattishall Golf Club Limited | Arts & recreation | 2005 |
| Mattishall Healthcare Limited | Health & social care | 1998 |
| Mayfield Recruitment Services Ltd | Administrative & support | 2024 |
| MB Auto Technic Centre Ltd | Wholesale & retail | 2020 |
| MBC Roofing & Vans Ltd | Construction | 2021 |
| MC Cars Limited | Wholesale & retail | 2024 |
| Mcclay Engineering Limited | Agriculture & fishing | 2016 |
| Mccormick Creative Limited | Professional & scientific | 2008 |
| Mcgrath Street Works Ltd | Construction | 2016 |
| Mcleod Aggregates Limited | Mining & quarrying | 2013 |
| Meadow View (Hockering) Management Limited | Households | 2006 |
| MED Stuff Ltd | Wholesale & retail | 2020 |
| Mededu Ltd | Education | 2023 |
| Medlock & Young Limited | Wholesale & retail | 2005 |
| Mektron Ltd | Agriculture & fishing | 2025 |
| Melhart Investments Ltd | Real estate | 2025 |
| Memtrad Ltd | Wholesale & retail | 2023 |
| Mena Edtech Alliance C.I.C. | Other services | 2025 |
| Mendham Plumbing & Heating Limited | Construction | 2008 |
| Mercer Engineering Limited | Other services | 1999 |
| Metaseed Ltd | Information & communication | 2019 |
| MFP Productions Limited | Administrative & support | 2007 |
| Mibar Properties Limited | Construction | 1999 |
| Mick Berry Services Ltd | Households | 2018 |
| MID Norfolk Accommodations Ltd | Real estate | 2023 |
| MID Norfolk Building Services Limited | Construction | 2009 |
| MID Norfolk Canopies and Trailers Ltd | Manufacturing | 2003 |
| MID Norfolk Heating Limited | Construction | 2016 |
| MID Norfolk Railway (Infrastructure & Engineering) Limited | Transport & logistics | 2018 |
| Mid-Norfolk Mencap | Health & social care | 1994 |
| Mid-Norfolk Pheasantries Limited | Agriculture & fishing | 2013 |
| Middle East Capital Ltd | Administrative & support | 2016 |
| Middleton Close Maintenance Limited | Administrative & support | 2009 |
| Mike Newman Haulage Limited | Transport & logistics | 2011 |
| Miles Rhodes Limited | Financial services | 2016 |
| Mill Lane Industrial Estates Limited | Real estate | 2019 |
| Millbrook First Ltd | Education | 2015 |
| Mills Macmillan Limited | Construction | 1992 |
| Minden Contracts Ltd | Transport & logistics | 2025 |
| Misty Window Repairs Norfolk Ltd | Construction | 2021 |
| Mitchell & Rollins Limited | Construction | 2002 |
| Mizen Holdco Limited | Financial services | 2019 |
| Mizen Limited | Professional & scientific | 2017 |
| MJE Property Ltd | Real estate | 2019 |
| MJH Contracting Limited | Transport & logistics | 2012 |
| MJM Classic Motorcycles Ltd | Wholesale & retail | 2022 |
| MJP Leisure Ltd | Administrative & support | 2009 |
| MJP Marketing Ltd | Administrative & support | 2007 |
| MJS Property Solutions Limited | Real estate | 2020 |
| Mkjg Limited | Transport & logistics | 2025 |
| ML Electrical (Norfolk) Limited | Construction | 2013 |
| Mmakizh Ltd | Wholesale & retail | 2025 |
| MNB Builders Ltd | Construction | 2017 |
| Mobile Arcade Ltd | Wholesale & retail | 2021 |
| Model Nutrition Dairy Consulting Ltd | Agriculture & fishing | 2010 |
| Momentum Learning Collaborative Limited | Education | 2026 |
| Mooney Demolition Co Ltd | Construction | 2012 |
| Mooney Demolition Properties Limited | Real estate | 2021 |
| Morley Aviaries Ltd. | Manufacturing | 2020 |
| Morphogenesis Research and Development Ltd | Information & communication | 2018 |
| Morphry Thyme Limited | Professional & scientific | 2021 |
| Mortgage Republic Limited | Financial services | 2016 |
| Morton Aviation Ltd | Manufacturing | 2019 |
| MOS CAN Limited | Hospitality | 2019 |
| Movable Technologies Limited | Information & communication | 2014 |
| Move (Norfolk) Ltd | Arts & recreation | 2026 |
| Movement, Mind and Motion Matters (M4 Group) CIC | Arts & recreation | 2024 |
| Movewell Apparel Ltd | Wholesale & retail | 2023 |
| MPH Groundworks Limited | Construction | 2003 |
| MR Carpentry and Partitioning Limited | Construction | 2019 |
| MR Skinsmith Ltd | Other services | 2025 |
| MR Tang 888 Ltd | Hospitality | 2023 |
| MR. P&S Enterprises Limited | Wholesale & retail | 2024 |
| Mrcp Ltd | Transport & logistics | 2022 |
| MRH Plumbing & Heating (Norfolk) Limited | Construction | 2017 |
| MS Fitting Services Ltd | Wholesale & retail | 2024 |
| MSM Property Services Limited | Real estate | 2005 |
| MSM Safety Management Services (U.K.) Ltd. | Professional & scientific | 1998 |
| MST Driving Services Limited | Transport & logistics | 2014 |
| Munnsbuild Ltd | Construction | 2025 |
| MW Bolting Solutions Ltd | Wholesale & retail | 2023 |
| Mwabu Group Ltd | Education | 2016 |
| Myhill Consulting Ltd | Professional & scientific | 2015 |
| Mysugarfix Ltd | Hospitality | 2024 |
| N & N Property East Anglia Limited | Real estate | 2023 |
| N Mold Limited | Real estate | 2012 |
| N. J. Allen Builders Limited | Construction | 2025 |