| Metfield Limited | Agriculture & fishing | 2013 |
| MGF Consult UK Ltd | Financial services | 2016 |
| MH Music Holdings Ltd | Information & communication | 2025 |
| MI VET Club Limited | Professional & scientific | 2013 |
| MI Window Cleaner Ltd | Administrative & support | 2019 |
| MIA Nails TH Ltd | Other services | 2024 |
| Michelle Denny Recruitment Limited | Administrative & support | 2019 |
| Microturbines Ltd | Professional & scientific | 2026 |
| Midwich Employees' Trustees Limited | Professional & scientific | 2004 |
| Midwich Group PLC | Wholesale & retail | 2013 |
| Midwich International Limited | Financial services | 2020 |
| Midwich Limited | Wholesale & retail | 1979 |
| Midwinter Furniture Ltd | Manufacturing | 2022 |
| Millennium Pest Control Limited | Other services | 2000 |
| Mindeful Mood Ltd | Manufacturing | 2024 |
| Minh and Jade Healthcare Ltd | Health & social care | 2024 |
| Mitson Close Management Company Limited | Households | 2025 |
| Mix-A-Man Limited | Manufacturing | 1999 |
| ML IT Solutions Ltd | Information & communication | 2017 |
| MM Brickwork Ltd | Construction | 2021 |
| Mobile Phone Repairs Diss Ltd | Other services | 2022 |
| Moca Vintage Ltd | Wholesale & retail | 2024 |
| Modern Vehicle Technology Limited | Wholesale & retail | 1993 |
| Mohdee Ltd | Real estate | 2023 |
| Monellies Hair and Beauty Limited | Other services | 2008 |
| Moneymatters 2 U UK Limited | Financial services | 2006 |
| Moon Digital Design Limited | Information & communication | 2024 |
| Moons (Suffolk) Limited | Other services | 2013 |
| Moreves Barn Limited | Administrative & support | 2014 |
| Morgan Moss International Limited | Wholesale & retail | 1999 |
| Mosaic Home Renovations Ltd | Real estate | 2021 |
| Motionaid Limited | Arts & recreation | 2012 |
| Mountfield Property Investments Ltd. | Real estate | 2022 |
| Mreidsfx/Sp Ltd | Information & communication | 2021 |
| MRS Clarke's General Store Ltd | Wholesale & retail | 2019 |
| MSR Pine Ltd | Hospitality | 2025 |
| MT Aves and SON (Holdings) Limited | Professional & scientific | 2012 |
| MTM Youth Services CIC | Health & social care | 2011 |
| Mullen Race Engineering Ltd | Professional & scientific | 2022 |
| Mustard HR Ltd | Administrative & support | 2019 |
| My Period Ltd. | Health & social care | 2019 |
| My Printing Supplies Ltd | Wholesale & retail | 2016 |
| My Taxi LOG Ltd | Information & communication | 2026 |
| NAP Site Services Ltd | Professional & scientific | 2024 |
| Napolina Dent Limited | Health & social care | 2025 |
| Natural Foodstore Co-Operative Ltd. | Wholesale & retail | 2017 |
| Natural Spa Supplies Limited | Wholesale & retail | 2007 |
| Natural Swimming Pools Ltd | Administrative & support | 2019 |
| Nature & Nurture Therapeutic Services Limited | Other services | 2016 |
| NBR Mobility Ltd | Manufacturing | 2010 |
| Nctpo Trading Limited | Professional & scientific | 2025 |
| ND Caravans Ltd | Wholesale & retail | 2024 |
| ND Environmental & Training Ltd | Professional & scientific | 2026 |
| Neil Gillis Limited | Real estate | 2007 |
| Neils Hairdressers Limited | Other services | 2003 |
| Nelson-Graham Consultants Limited | Education | 2014 |
| Nestbrik Ltd | Construction | 2022 |
| Network Sales & Solutions Limited | Information & communication | 1984 |
| Neuropath Clinical Services Ltd | Health & social care | 2026 |
| New Conduit Portfolio Limited | Real estate | 2013 |
| New Day New Way Ltd | Education | 2026 |
| New Moon Photography Limited | Professional & scientific | 2002 |
| New World Music Limited | Information & communication | 1997 |
| New World Music Publishing Limited | Information & communication | 1997 |
| Newman Family Investments Limited | Real estate | 2021 |
| Nexusfuse Ltd | Information & communication | 2015 |
| Nielsen Design Limited | Wholesale & retail | 1998 |
| Nightkeeper Productions Limited | Wholesale & retail | 2018 |
| Nights Investments Ltd | Real estate | 2019 |
| Nikobim Limited | Professional & scientific | 2025 |
| Nimans Limited | Information & communication | 1985 |
| NJM Commercial Ltd | Wholesale & retail | 2026 |
| Noctua Limited | Real estate | 2011 |
| Nodescape Limited | Information & communication | 2022 |
| Nomad Developments Ltd | Real estate | 2023 |
| North Common Commercial Ltd | Wholesale & retail | 2021 |
| Norwich Accountancy and Bookkeeping Services Ltd | Professional & scientific | 2020 |
| Norwich Open Christmas Limited | Hospitality | 2011 |
| Notsallow 196 Limited | Real estate | 2003 |
| Novum Holdings UK Limited | Financial services | 2007 |
| NR Group East Anglia Ltd | Information & communication | 2020 |
| Number 11 Diss Limited | Hospitality | 2018 |
| O J Coles Limited | Construction | 2017 |
| O.M.P Trading Limited | Administrative & support | 2022 |
| Oakhall Lodge Limited | Real estate | 2016 |
| Oakland Enterprises Limited | Professional & scientific | 2019 |
| Oakland Property Group Limited | Construction | 2024 |
| Oakley Air Conditioning Services Ltd | Construction | 2022 |
| Oakley Diss Limited | Education | 2003 |
| Oakley Property Rentals Ltd | Real estate | 2025 |
| Ogpaintwork Ltd | Construction | 2025 |
| Okeford Veterinary Centre Limited | Professional & scientific | 2006 |
| Old Station Hotel Management Limited | Households | 2007 |
| Olichlo Property Limited | Real estate | 2016 |
| Olive Court Developments Limited | Households | 2015 |
| Oliver Klinefelter Racing Limited | Arts & recreation | 2025 |
| Omniscient Data Services Ltd | Information & communication | 2025 |
| ON OUR Terms Ltd. | Hospitality | 2025 |
| ON the HUH Ltd | Professional & scientific | 2021 |
| One for the Road Hospitality Limited | Hospitality | 2017 |