| Number 9 Project CIC | Health & social care | 2023 |
| Number One Drinks Company Limited | Wholesale & retail | 2006 |
| Number-Wise Ltd | Administrative & support | 2025 |
| Numbereight Technologies Ltd | Information & communication | 2016 |
| Nuranna Ltd | Professional & scientific | 2025 |
| Nuray Ltd | Hospitality | 2019 |
| Nurse Annie Aesthetic Clinic Ltd | Other services | 2025 |
| Nurse Meicha Ltd | Other services | 2022 |
| Nursery Park Residents Association Limited | Households | 1976 |
| Nursery Universe Ltd | Wholesale & retail | 2025 |
| Nurture & Thrive Norfolk Wellbeing Ltd | Health & social care | 2026 |
| Nurture Bridge Social Care Ltd | Health & social care | 2026 |
| Nurture Clean Services Ltd | Wholesale & retail | 2025 |
| Nurture Digital Ltd | Information & communication | 2013 |
| Nurture Health and Care Ltd | Public administration | 2021 |
| Nushrat Catering Ltd | Hospitality | 2018 |
| Nutmeg Installations Limited | Administrative & support | 2025 |
| Nutridoc Ltd | Health & social care | 2019 |
| Nutrition Authority Ltd | Health & social care | 2025 |
| Nutrition Revolution Ltd | Health & social care | 2021 |
| Nuttha Limited | Professional & scientific | 2016 |
| Nuttura Ltd. | Manufacturing | 2026 |
| Nuvexo Ltd | Wholesale & retail | 2025 |
| Nuwave Promotions Limited | Arts & recreation | 2023 |
| Nv-Ar Radiology Services Limited | Health & social care | 2026 |
| NVSM24 Ltd | Professional & scientific | 2024 |
| NVT CIC | Administrative & support | 2017 |
| Nvwa Robotics Ltd | Administrative & support | 2023 |
| NW & B De'Ath Limited | Hospitality | 2009 |
| NW Cars Norwich Ltd | Wholesale & retail | 2025 |
| Nwbp Management Limited | Real estate | 2026 |
| NWD Norwich Holdings Ltd | Financial services | 2024 |
| Nwhp Limited | Real estate | 2013 |
| NWW Services Limited | Administrative & support | 2025 |
| NYA Group Ltd | Financial services | 2025 |
| NYA Moorings Limited | Real estate | 2014 |
| NYA Service Centre Limited | Manufacturing | 2000 |
| NYE Cleaning Services Ltd | Administrative & support | 2007 |
| Nyos Properties Ltd | Real estate | 2019 |
| Nysacx Group Limited | Financial services | 2025 |
| Nysdill Accommodation Ltd | Hospitality | 2024 |
| Nyvelle Ltd | Wholesale & retail | 2026 |
| NZ Outdoors Limited | Wholesale & retail | 2016 |
| NZC Services Ltd | Professional & scientific | 2020 |
| Nzuko Igbo Norwich Limited | Other services | 2025 |
| O a Chapman & SON Limited | Administrative & support | 2003 |
| O P Bunn Limited | Professional & scientific | 2015 |
| O Studio Ltd | Administrative & support | 2015 |
| O Todd Services Ltd | Wholesale & retail | 2026 |
| O'Brien Racing Solutions Limited | Wholesale & retail | 2021 |
| O'Brien Renewable Solutions Limited | Professional & scientific | 2014 |
| O'Farrell Design & Development Limited | Professional & scientific | 2015 |
| O'Neill's Estates Ltd | Real estate | 2020 |
| O'Sullivan Resources Limited | Mining & quarrying | 2008 |
| O-Ja Productions Ltd | Administrative & support | 2016 |
| O-Tech Electrical Services Limited | Construction | 2020 |
| O.Co.Partner Ltd | Administrative & support | 2021 |
| O.F.F. Shire Management Ltd | Extraterritorial | 2010 |
| O.R.M. North Norfolk Limited | Water & waste | 2003 |
| OA7 Limited | Wholesale & retail | 2022 |
| Oak Drive (Filby) Management Company Limited | Households | 2025 |
| Oak Hill Flooring Limited | Construction | 2017 |
| Oak Lettings (EA) Ltd | Real estate | 2026 |
| Oak Lodge Business Centre Limited | Construction | 2011 |
| Oak Management (Norwich) Limited | Households | 1999 |
| Oak Park Farms Limited | Agriculture & fishing | 1999 |
| Oak Sparkle Services Limited | Administrative & support | 2026 |
| Oak Street Management Limited | Households | 1984 |
| Oak Tree Financial Planning Limited | Financial services | 2010 |
| Oak View Cattery Ltd | Other services | 2025 |
| Oak View Grove Management Co Limited | Households | 2020 |
| Oak Willow Properties Ltd | Real estate | 2024 |
| Oakauri Projects Limited | Professional & scientific | 2015 |
| Oakbrow Ltd | Health & social care | 2018 |
| Oakcroft Building Services Limited | Construction | 2021 |
| Oakey & Sons Property Ltd | Hospitality | 2017 |
| Oakfield Arboricultural Services Limited | Construction | 2014 |
| Oakfield Building Services (East) Ltd | Construction | 2023 |
| Oakhill Residents Limited | Households | 2021 |
| Oakhurst-Winfield Ltd | Information & communication | 2021 |
| Oaklair Limited | Manufacturing | 1981 |
| Oakleigh Watches Ltd | Wholesale & retail | 2014 |
| Oakley Design and Build Norfolk Limited | Construction | 2022 |
| Oaklink Limited | Wholesale & retail | 2026 |
| Oakmount Homes Ltd | Construction | 2019 |
| Oakmount Residential Ltd | Real estate | 2022 |
| Oaks and Apple Ltd | Information & communication | 2018 |
| Oaktree Holidays Ltd | Real estate | 2022 |
| Oaktree Property Group Ltd | Real estate | 2022 |
| Oakwood Building Developments (Norfolk) Ltd | Construction | 2021 |
| Oakwood House (Norwich) Ltd | Health & social care | 2019 |
| Oakwood Risk and Resilience Ltd | Administrative & support | 2019 |
| Oakwood Tyres Ltd | Wholesale & retail | 2020 |
| OAS Medical Limited | Health & social care | 2022 |
| Oasis (Norwich) Blinds & Construction Management Limited | Construction | 2006 |
| Oasis East Anglia Limited | Construction | 2021 |
| Oasis Holiday Village Limited | Hospitality | 2023 |
| Oasis Trading (Commodities) Limited | Hospitality | 2009 |
| Oath! the Real Food Company Limited | Manufacturing | 2025 |
| Obase-Aboli Music Ltd | Information & communication | 2021 |