| Nine Locks (Vehicle Dismantlers) Limited | Other services | 1976 |
| Nippyshop Ltd | Wholesale & retail | 2020 |
| NJE Holdings Ltd | Professional & scientific | 2021 |
| NJL Fire Solutions Ltd | Professional & scientific | 2026 |
| NJN Property Group Ltd | Real estate | 2026 |
| NK TM Ltd | Construction | 2022 |
| NL Tutoring Ltd | Education | 2024 |
| NLD Contractors Ltd | Information & communication | 2008 |
| NO1 House Clear Ltd | Water & waste | 2025 |
| Noakes Family Holdings Limited | Real estate | 2018 |
| NOBLE54 Ltd | Wholesale & retail | 2025 |
| NOBLEHOUSEPARTRIK71 Limited | Hospitality | 2024 |
| Nock Properties Limited | Real estate | 2016 |
| Nocomoto Ltd | Professional & scientific | 2020 |
| Nocturnal Works Ltd | Manufacturing | 2018 |
| Nokell Fabrications Limited | Manufacturing | 2002 |
| Noonan Fire & Security Limited | Construction | 2022 |
| Noralynn Consultancy Ltd | Health & social care | 2018 |
| Norrice Finance Limited | Financial services | 2016 |
| Nortech Engineering & Automation Ltd | Manufacturing | 2011 |
| Northtrade Ltd | Wholesale & retail | 2026 |
| Northverge Services Ltd | Administrative & support | 2026 |
| Northwest Goldsmiths Ltd | Wholesale & retail | 2024 |
| Northwood Office Solutions Limited | Real estate | 2016 |
| Norton Farm Management Company Limited | Households | 2016 |
| Nostalgia Inns Limited | Administrative & support | 2000 |
| Nostrabell Limited | Construction | 1978 |
| Nova Acquisition Limited | Financial services | 2016 |
| Novaedge Solutions Ltd | Information & communication | 2026 |
| Novex Service Solutions Ltd | Administrative & support | 2026 |
| NR 2015 Holdings Limited | Real estate | 2015 |
| NR Convenience Retail Limited | Wholesale & retail | 2026 |
| Nrgc Limited | Real estate | 2010 |
| NSC Building Solutions Ltd | Construction | 2022 |
| NSH Investments Ltd | Real estate | 2015 |
| Nu-Clear Windows Ltd | Construction | 2021 |
| Nu-View Windows & Doors Limited | Construction | 2014 |
| Nu-Weld Engineering Services Holdings Limited | Financial services | 2020 |
| Nu-Weld Engineering Services Limited | Manufacturing | 1995 |
| Number 78 Ltd | Professional & scientific | 2023 |
| Nunnal Developments Ltd | Construction | 2021 |
| NUT and Block Properties Ltd | Real estate | 2021 |
| Nutrify Limited | Administrative & support | 2006 |
| Nuvo Outdoor Living Limited | Wholesale & retail | 2023 |
| Nyatech Limited | Information & communication | 2022 |
| O.M.P. Enterprise Ltd | Health & social care | 2010 |
| O0NE Clothing Limited | Wholesale & retail | 2023 |
| Oak Furniture King Limited | Extraterritorial | 2012 |
| Oak Lodge Doors Ltd | Wholesale & retail | 2015 |
| Oakers Consultancy Ltd | Extraterritorial | 2015 |
| Oakleigh Contracts Limited | Construction | 2018 |
| Oakwood Estate Management Company Limited | Households | 1982 |
| Oasis Hajj & Umrah Limited | Administrative & support | 2013 |
| OBC Equipment Ltd | Professional & scientific | 2014 |
| Occo Reddon Limited | Wholesale & retail | 2019 |
| Occupational Health Perspectives Limited | Health & social care | 2016 |
| Ocuplan Limited | Health & social care | 2019 |
| Oftb Ltd | Professional & scientific | 2020 |
| OH Baby Preloved Ltd | Wholesale & retail | 2024 |
| Ohana Events Ltd | Wholesale & retail | 2019 |
| OHC Consultancy Limited | Health & social care | 2010 |
| Old and Broken Ltd | Wholesale & retail | 2022 |
| Old Art School Limited | Construction | 2016 |
| Old Halesonians RFC Ltd | Arts & recreation | 2014 |
| Oldbury Garage Limited | Wholesale & retail | 2006 |
| Oliam Property Limited | Real estate | 2013 |
| Olive Translations Limited | Professional & scientific | 2008 |
| Oliver and Springer Advisory Limited | Professional & scientific | 2025 |
| Olton Hollow Limited | Professional & scientific | 2014 |
| Olympia Test & Crane Limited | Professional & scientific | 2014 |
| Omaye Consultancy Limited | Professional & scientific | 2024 |
| Omnis 1 Limited | Construction | 2022 |
| Oncosearch Ltd | Administrative & support | 2025 |
| One BED Flat Ltd | Extraterritorial | 2019 |
| One Link Properties Limited | Real estate | 2025 |
| One Plus Two Limited | Real estate | 2001 |
| One Roof Services Group Limited | Construction | 2026 |
| One Stop Fabrication Shop Limited | Manufacturing | 2014 |
| One Thirty Ltd | Extraterritorial | 2019 |
| Onlive Ltd | Information & communication | 2016 |
| Opensons Limited | Real estate | 2021 |
| Operation Management Ltd | Professional & scientific | 2024 |
| Ophthalmologica Investments Limited | Professional & scientific | 2013 |
| Optalisha Limited | Health & social care | 2014 |
| Optimus Flooring Limited | Wholesale & retail | 2019 |
| Opulent Capital | Financial services | 2017 |
| OQ Projects (Halesowen) Ltd | Arts & recreation | 2017 |
| Oral Surgery & Sedation Limited | Health & social care | 2026 |
| Organpak (1987) Limited | Professional & scientific | 1987 |
| Orthoracle Limited | Education | 2015 |
| Orton Electrical & Mechanical Group Limited | Professional & scientific | 2014 |
| Orton Electrical Services Limited | Construction | 2001 |
| Orton Maintenance Limited | Construction | 2014 |
| Orton Mechanical Services Limited | Construction | 2010 |
| Orton Technical Services Limited | Extraterritorial | 2016 |
| Oryx Engineering & Installation Limited | Administrative & support | 2011 |
| Osbourne House Apartments Ltd | Real estate | 2025 |
| Osprey Fabrications Limited | Construction | 1999 |
| Osto Health Limited | Health & social care | 2020 |
| Oswestry Electrical & Plumbing Factors Limited | Wholesale & retail | 1990 |