| Nadine Clare Limited | Wholesale & retail | 2021 |
| Nannas Ltd | Education | 2005 |
| Nannas Nurseries Limited | Education | 2013 |
| Native Teams Solutions Limited | Information & communication | 2024 |
| Natural Preston Limited | Households | 2020 |
| Nautica RTM Company Limited | Households | 2018 |
| Navigator IP Limited | Information & communication | 2019 |
| Navigator Licensing Limited | Information & communication | 2019 |
| Nbitc Media Ltd | Information & communication | 2025 |
| Nethergate Brewery Co Ltd | Manufacturing | 2014 |
| Netsymphony Limited | Information & communication | 2008 |
| Netvista Ltd | Information & communication | 2014 |
| Network Data Cabling Limited | Information & communication | 2017 |
| Neutron Consult Ltd | Professional & scientific | 2019 |
| New Concept Motors Limited | Wholesale & retail | 2019 |
| New Works Limited | Administrative & support | 2016 |
| NEW2UHOMES Ltd | Construction | 2013 |
| Newbury Court (Ilford) Management Company Limited | Households | 2001 |
| Newco Advisory Limited | Financial services | 2015 |
| Newmarket Equine Referrals Limited | Professional & scientific | 2022 |
| Newton Grove Management Company Limited | Households | 2019 |
| Newton Grove Phase 2 Limited | Real estate | 2021 |
| Newton Leys Barns Ltd | Construction | 2026 |
| Newtonium Ltd | Information & communication | 2021 |
| Newtons Medical Supplies Ltd | Wholesale & retail | 2015 |
| Next Car 4 Less Limited | Wholesale & retail | 2009 |
| Nexus Energy Ltd | Construction | 2012 |
| Nick HP Limited | Professional & scientific | 2019 |
| Nick Peasland Architectural Services Limited | Professional & scientific | 2012 |
| Nicolewm Services Limited | Administrative & support | 2018 |
| Nine Nevill Park Limited | Extraterritorial | 1978 |
| NJV Enterprises (London) Limited | Construction | 2013 |
| NLA VW Parts Ltd | Wholesale & retail | 2013 |
| NN71 Ltd | Construction | 2020 |
| NO 6.CAMBALT Road Management Company Limited | Households | 1966 |
| NO 633 Management Company Limited | Households | 2012 |
| Noble House Services (UK) Limited | Construction | 2003 |
| Noble House Services Trustee Limited | Extraterritorial | 2025 |
| Nodding Frog Limited | Information & communication | 2014 |
| NOG UK Limited | Real estate | 2025 |
| Nomina Registrars Limited | Professional & scientific | 1999 |
| Normanhurst Mansions Limited | Households | 2004 |
| Norris & Co Plumbing & Heating Limited | Construction | 2021 |
| Nosmo Ventures Limited | Real estate | 2013 |
| Nosmotech Limited | Financial services | 2021 |
| Nous Media Limited | Administrative & support | 2021 |
| Nova Vend Ltd | Wholesale & retail | 2024 |
| Novaabay Ltd | Wholesale & retail | 2024 |
| Novagro Limited | Manufacturing | 2024 |
| Novara Consulting Ltd | Information & communication | 2025 |
| Novp Limited | Information & communication | 2024 |
| NSM Property Limited | Real estate | 2022 |
| Oak, ASH and Thorn Contracting Ltd | Agriculture & fishing | 2025 |
| Oakhouse Foods East Anglia Limited | Hospitality | 2017 |
| Oakley Lodge Community Ltd | Households | 2021 |
| Oakmore Private Works Ltd | Construction | 2026 |
| Oakview Drinks Company Ltd | Manufacturing | 2025 |
| Obra Ltd | Construction | 2018 |
| Oceanfront Global Marketing Limited | Wholesale & retail | 2009 |
| Oceanial Community Interest Company | Agriculture & fishing | 2014 |
| Ockford Court Residents Association Limited | Households | 1972 |
| Oconnolly's Ltd | Professional & scientific | 2019 |
| Octavia Technique Limited | Extraterritorial | 2013 |
| ODD Socks Fulfillment and Storage Solutions Ltd | Transport & logistics | 2025 |
| Odyssey Sound System Records Ltd | Administrative & support | 2023 |
| OFF the Wall Squash CIC | Arts & recreation | 2014 |
| OFF the Wall Squash International Ltd | Arts & recreation | 2022 |
| Offcampus Ltd | Wholesale & retail | 2024 |
| Offshoot Films (2017) Ltd | Administrative & support | 2017 |
| Offworld Limited | Professional & scientific | 2020 |
| Old and Modern Vintage and Collectables Ltd | Wholesale & retail | 2025 |
| Old Market Court Property Management Limited | Real estate | 1988 |
| Old School GC C.I.C. | Administrative & support | 2022 |
| Old Waterworks Glamping Ltd | Hospitality | 2022 |
| Oldbury Engineering Co.,Limited | Manufacturing | 1946 |
| Oldspeak Limited | Wholesale & retail | 2025 |
| Oliecom Limited | Transport & logistics | 2012 |
| Oliphant & Miller Ltd | Construction | 2024 |
| Olive Branch Developments Ltd | Construction | 2026 |
| Olive Octagon Limited | Information & communication | 2024 |
| Omercove Limited | Administrative & support | 2023 |
| One Five Nine Property Management Ltd | Professional & scientific | 2014 |
| One Granville Park Limited | Households | 2001 |
| Onecoat Limited | Hospitality | 2026 |
| Onib SPV Ltd | Information & communication | 2023 |
| Onthank Ltd | Professional & scientific | 2018 |
| Onward Advisory Limited | Professional & scientific | 2026 |
| Openbox Group Ltd | Administrative & support | 2016 |
| Option 4 Ltd | Transport & logistics | 2022 |
| Orbell Developments Limited | Construction | 2014 |
| Original Theatre Commercial Enterprises Ltd | Arts & recreation | 2013 |
| Original Theatre Productions Ltd | Arts & recreation | 2018 |
| Ortus Marine Services Limited | Other services | 2016 |
| Ortus Technology Limited | Wholesale & retail | 2011 |
| Ortus Technology Trustee Limited | Extraterritorial | 2025 |
| Ortus Telematics Ltd | Information & communication | 2016 |
| Osborne Building & Renovations Ltd | Construction | 2025 |
| Osborne Toureau Trading Ltd | Professional & scientific | 2020 |
| Oscars Whippy Limited | Hospitality | 2024 |
| OSG Services Ltd | Transport & logistics | 2014 |