| Nifty Services Ltd | Administrative & support | 2024 |
| Nightingale (Balham) Management Company Limited | Households | 2013 |
| Nightingale Residential Care Home Ltd | Health & social care | 2005 |
| Nightingale View (Hamstreet) Management Company Limited | Households | 2022 |
| Nikicare Limited | Health & social care | 2024 |
| Nipu & SON Ltd | Hospitality | 2023 |
| NJM Homes Ltd | Real estate | 2023 |
| NJN Enterprises Ltd | Wholesale & retail | 2025 |
| NL Jones Holdings Limited | Hospitality | 2025 |
| Nnrk Trading Ltd | Wholesale & retail | 2022 |
| Nnrr Relocation Properties Limited | Real estate | 2021 |
| NO Denial Limited | Wholesale & retail | 2021 |
| NO Dust "R"Us Ltd | Administrative & support | 2022 |
| Noble Global Results Limited | Administrative & support | 2010 |
| Nocturne Notes Limited | Arts & recreation | 2012 |
| Noir Continental Ltd | Transport & logistics | 2025 |
| Nolan Homes Essex Ltd | Real estate | 2025 |
| NOM Southend Ltd | Hospitality | 2025 |
| Nomic Digital Ltd | Information & communication | 2018 |
| Nonsuch House Airspace Limited | Real estate | 2022 |
| Noorzai Ltd | Energy | 2025 |
| Nordic Publishing Holding Limited | Information & communication | 2019 |
| Norm Consultants Limited | Real estate | 1997 |
| Normanton Heights (Croydon) Management Company Limited | Households | 2012 |
| Nortech Technologies Ltd. | Other services | 2017 |
| North Devon Waves Limited | Hospitality | 2020 |
| North Essex Finance Limited | Financial services | 2002 |
| North London Contractor Ltd | Construction | 2017 |
| North London MOT Centre Ltd | Wholesale & retail | 2022 |
| North Star Executives Ltd | Information & communication | 2023 |
| North West Region Assets Limited | Extraterritorial | 2003 |
| Northarena Ltd | Wholesale & retail | 2023 |
| Northcore Newco Limited | Extraterritorial | 2023 |
| Northumberland Developments Essex Limited | Construction | 2019 |
| Norwood Road Property Ltd | Households | 2024 |
| Nosce TE Ipsum Limited | Health & social care | 2025 |
| Notorious Events Limited | Information & communication | 2022 |
| Notting Hill Antiques Company Limited | Wholesale & retail | 2015 |
| Nova Circular Capital Ltd | Administrative & support | 2025 |
| Nova Electrics Ltd | Construction | 2023 |
| Nova Events Limited | Arts & recreation | 2016 |
| Nova Eyecare Ltd | Health & social care | 2026 |
| Nova Luxury Ltd | Wholesale & retail | 2023 |
| Novagard Consulting Ltd | Professional & scientific | 2024 |
| Novation Ltd | Information & communication | 2010 |
| Novo Deck Ltd | Construction | 2020 |
| Novum Drylining Ltd | Construction | 2026 |
| NP Collective Limited | Other services | 2017 |
| Npos Limited | Wholesale & retail | 2011 |
| NPS Design Build Limited | Construction | 2012 |
| NRF Solutions Limited | Professional & scientific | 2025 |
| Nserv Ltd | Construction | 2018 |
| NSS Medik Ltd | Health & social care | 2012 |
| NT Dance House Limited | Education | 2026 |
| NTH 24 Limited | Real estate | 2024 |
| Nursery Thymes Two Limited | Other services | 2001 |
| NVR Aesthetics Ltd | Other services | 2022 |
| NVR Media Ltd | Professional & scientific | 2021 |
| NXT GEN International Holdings Limited | Financial services | 2021 |
| OAB Fashion Limited | Wholesale & retail | 2017 |
| Oak House Montessori Limited | Administrative & support | 2008 |
| Oak Lodge Care Ltd | Health & social care | 2019 |
| Oak Share Ltd | Professional & scientific | 2017 |
| Oak Tree Market Limited | Hospitality | 2013 |
| Oakapple 2 Resident Management Company Limited | Households | 2023 |
| Oakdales Limited | Professional & scientific | 2000 |
| Oakleigh Autos Limited | Real estate | 1961 |
| Oakleigh Lodge RTM Company Limited | Households | 2014 |
| Oakview Green Management Company Limited | Households | 2025 |
| Oasis Bidco Limited | Financial services | 2018 |
| Oasis Care Services Limited | Health & social care | 1999 |
| Oasis Midco Limited | Financial services | 2018 |
| Oasis Supported Housing C.I.C. | Health & social care | 2018 |
| Oasis Supported Living Limited | Health & social care | 2015 |
| Oasis Topco Limited | Financial services | 2018 |
| Obee Ltd | Health & social care | 2013 |
| Ocean Maintenance Limited | Construction | 2019 |
| Ogole Morgan Ltd | Professional & scientific | 2022 |
| OHB Ltd | Real estate | 2022 |
| Okavango Limited | Professional & scientific | 2025 |
| Olbc Contracting Limited | Construction | 2011 |
| Oldhams of Westcliff Limited | Hospitality | 2007 |
| Olive & Buck Limited | Wholesale & retail | 2016 |
| Olive Private Health Limited | Real estate | 2023 |
| Olivia CM Ltd | Health & social care | 2023 |
| Olivo OIL Ltd | Wholesale & retail | 2025 |
| Olly Dobson Ltd | Information & communication | 2017 |
| Olma Fine Foods Limited | Manufacturing | 2018 |
| Olma Invest (UK) Limited | Professional & scientific | 2018 |
| Oloko Holdings Limited | Professional & scientific | 2025 |
| OLS Group Limited | Construction | 2025 |
| OLV Limited | Professional & scientific | 2022 |
| OLV Properties Limited | Real estate | 2022 |
| Olympus Global Treasury Services Limited | Administrative & support | 2010 |
| Olympus Keymed Group Limited | Professional & scientific | 1975 |
| Omega Management Services Limited | Professional & scientific | 2023 |
| Omniant Ltd | Information & communication | 2026 |
| Omnidom Group Ltd | Professional & scientific | 2026 |
| Omnilife Ltd | Wholesale & retail | 2021 |
| Omron Estates Limited | Real estate | 2015 |