| Newold Plant Ltd | Administrative & support | 2019 |
| Nexas Star Ltd | Hospitality | 2026 |
| Nexus Capital Inc Ltd | Wholesale & retail | 2026 |
| Nexus Cloud Solutions Ltd | Information & communication | 2024 |
| Nexus Sales Limited | Wholesale & retail | 2023 |
| Nexusworks Consulting Limited | Construction | 2023 |
| NFS Facilities Services Ltd | Education | 2019 |
| NG Actio Limited | Professional & scientific | 2023 |
| NG Builders Ltd | Construction | 2016 |
| NGC Project Partners Limited | Professional & scientific | 2023 |
| Niadira Ltd | Wholesale & retail | 2021 |
| Niazi Properties Limited | Real estate | 2018 |
| Nicholas Jupp Limited | Administrative & support | 2014 |
| Nicola Simpson Executive Coaching Limited | Professional & scientific | 2017 |
| Nicolas Clerc Limited | Hospitality | 2016 |
| Nigel Clement Legal Services Ltd | Professional & scientific | 2011 |
| Nightingale Communications Limited | Information & communication | 2009 |
| Nightjar Properties Limited | Real estate | 2019 |
| Nikcheya Food Ltd | Wholesale & retail | 2026 |
| Ninian Park Rail Limited | Other services | 2017 |
| NJ Homes Ltd | Real estate | 2019 |
| NJE Controls Limited | Professional & scientific | 2014 |
| NKM Holdings Limited | Financial services | 2020 |
| Nkmz International Projects Limited | Administrative & support | 2009 |
| NKS Electrical Services Limited | Administrative & support | 2023 |
| NLT Renovations Ltd | Real estate | 2025 |
| NM Cooper Limited | Wholesale & retail | 2022 |
| NN & Y Ltd | Other services | 2020 |
| NNN Electrical Limited | Construction | 2007 |
| NO Child Hungry Global Community Interest Company | Health & social care | 2026 |
| NO1CONTRACTORLONDON Limited | Construction | 2016 |
| Noble Emporium Ltd | Wholesale & retail | 2024 |
| Nolo Nocere Limited | Real estate | 2021 |
| Nomad Risk Ltd | Administrative & support | 2018 |
| Noon Investments Ltd | Real estate | 2024 |
| North C Properties Limited | Real estate | 2020 |
| North Cray Equestrian Centre Limited | Other services | 2015 |
| Northstar 73 Electrical Services Limited | Construction | 2021 |
| Northstar Electrical Services Limited | Construction | 2025 |
| Nosh Pots Ltd | Wholesale & retail | 2026 |
| Nosu Studio Ltd | Information & communication | 2025 |
| NOT SO Limited | Health & social care | 2018 |
| Note Perfect Music Ltd | Arts & recreation | 2003 |
| Notthampton Limited | Real estate | 2012 |
| Novo Services Limited | Construction | 2024 |
| Novodian Group Ltd | Information & communication | 2026 |
| NP Consultants Limited | Professional & scientific | 2022 |
| NP Loft Conversion Limited | Construction | 2022 |
| NP Manufacturing Limited | Manufacturing | 2001 |
| NPJ Consultancy Services Limited | Professional & scientific | 2018 |
| NSH Property Consultants Limited | Construction | 2009 |
| NSL Estates Ltd | Real estate | 2026 |
| NSM (Sidcup) Limited | Wholesale & retail | 1997 |
| Nuclear Oncology UK Ltd. | Professional & scientific | 2022 |
| Nuffield Workday Ltd | Other services | 2025 |
| Nuovo K Limited | Wholesale & retail | 2021 |
| Nusher Consulting Ltd | Professional & scientific | 2021 |
| Nuukore Ltd | Arts & recreation | 2025 |
| NV Property Development Limited | Real estate | 2021 |
| NWK Capital Limited | Real estate | 2018 |
| Nyoung Limited | Public administration | 2023 |
| O & E Electrical Services Limited | Manufacturing | 2014 |
| O & E Plumbing Services Limited | Extraterritorial | 2014 |
| O & E Services Limited | Construction | 2005 |
| O Invest Ltd | Real estate | 2024 |
| O Investella JV Ltd | Real estate | 2024 |
| O Services Ltd | Financial services | 2024 |
| O'Neill Classics Limited | Administrative & support | 2025 |
| O'Neill Financial Consulting Limited | Professional & scientific | 2023 |
| O'Shea Brothers (Old Rectory) Ltd | Real estate | 2024 |
| O'Shea Brothers (Brook House) Ltd | Real estate | 2023 |
| O'Shea Brothers (Dutton Close) Ltd | Real estate | 2023 |
| O'Shea Brothers (Duttons Close) Management Ltd | Households | 2025 |
| O'Shea Brothers (Herne Common) Ltd | Real estate | 2026 |
| O'Shea Brothers (ST James Road) Ltd | Real estate | 2026 |
| O'Shea Brothers (the Water Margin) Ltd | Real estate | 2024 |
| O'Shea Brothers Construction Ltd | Construction | 2024 |
| O'Shea Brothers Freehold Holdings Ltd | Financial services | 2025 |
| O'Shea Brothers Holdings Ltd | Real estate | 2021 |
| O'Shea Brothers Ltd | Real estate | 2021 |
| O'Sullivan IT Ltd | Information & communication | 2018 |
| O.C.L Property Co Limited | Real estate | 2020 |
| O.S.Smoke Shisha Lounge Limited | Hospitality | 2026 |
| Oakcroft Property Ltd | Real estate | 2022 |
| Oakhurst Travel Limited | Administrative & support | 1980 |
| Oakley Ventures Ltd | Administrative & support | 2023 |
| Oakway Landscapes Limited | Administrative & support | 2021 |
| Obabenin Consultancy Limited | Information & communication | 2019 |
| OBC London Limited | Construction | 2009 |
| Oblix Construction Ltd | Construction | 2025 |
| Ocean Plant Hire Limited | Households | 2016 |
| Octagon S.E. Ltd | Administrative & support | 2009 |
| Octant Project Management Limited | Construction | 2026 |
| Octopure DEL Maar Limited | Wholesale & retail | 2021 |
| ODH Climate & Maintenance Limited | Construction | 2025 |
| ODH Developments Limited | Construction | 2024 |
| ODH Services Limited | Administrative & support | 2014 |
| Oehler Design Ltd | Professional & scientific | 2015 |
| Ogunsola Ltd | Financial services | 2017 |
| Ohmtech Ltd | Energy | 2014 |