| NX7 Support Ltd | Administrative & support | 2024 |
| NXB Management Consultancy Ltd | Financial services | 2019 |
| NXR Equity (Northern) Limited | Construction | 2026 |
| NXR Sovereign Projects Limited | Financial services | 2026 |
| NXT Step Fitness Ltd | Arts & recreation | 2024 |
| NY Healthcare Ltd | Health & social care | 2024 |
| NY Hot Wheels Ltd | Wholesale & retail | 2023 |
| Nyan Aesthetics Ltd | Other services | 2026 |
| Nyang Ltd | Wholesale & retail | 2024 |
| Nyanga CY Limited | Health & social care | 2021 |
| Nyasa Ltd | Professional & scientific | 2023 |
| Nyatate Ltd | Construction | 2026 |
| Nycleeds Ltd | Hospitality | 2026 |
| Nyco Leaflet Distribution Ltd | Transport & logistics | 2015 |
| NYK Properties Ltd | Real estate | 2023 |
| NYL Investors (U.K.) Limited | Financial services | 2000 |
| Nylex Gaming Ltd | Arts & recreation | 2024 |
| Nyman Green Limited | Agriculture & fishing | 2016 |
| Nyman Media Ltd | Professional & scientific | 2009 |
| Nyolo Healthcare Resources Limited | Health & social care | 2015 |
| Nypc ( UK ) Ltd | Manufacturing | 2020 |
| Nypd (KR) Limited | Real estate | 2017 |
| Nypd (SR) Limited | Real estate | 2022 |
| Nypd Franklin Road Limited | Real estate | 2012 |
| Nypd Group Limited | Professional & scientific | 2020 |
| Nypd Grove Road Limited | Real estate | 2015 |
| Nypd High Street Limited | Construction | 2013 |
| NZP Capital Partners Ltd | Real estate | 2025 |
| NZP Private Ltd | Health & social care | 2021 |
| NZP1 Ltd | Manufacturing | 2025 |
| NZP4 Ltd | Manufacturing | 2025 |
| O & MR Limited | Professional & scientific | 2025 |
| O F Network Services Limited | Information & communication | 2005 |
| O K S Williams Ltd | Real estate | 2026 |
| O L I Shine Limited | Administrative & support | 2026 |
| O L M Manchester Limited | Financial services | 2023 |
| O MAE Media Ltd | Professional & scientific | 2026 |
| O R Foods Limited | Hospitality | 2025 |
| O S Clarkson Limited | Financial services | 2021 |
| O Yeah Ltd | Wholesale & retail | 2020 |
| O&J Consultants Limited | Construction | 2023 |
| O'Connell Enterprises Limited | Real estate | 2011 |
| O'Delicesdappo Limited | Hospitality | 2024 |
| O'Donnell Assets Limited | Real estate | 2020 |
| O'Donovan Property Management Ltd | Real estate | 2024 |
| O'Fishleybaked Ltd | Manufacturing | 2022 |
| O'Garra Cohen Cramer Limited | Extraterritorial | 2019 |
| O'Garra Consulting Ltd | Real estate | 2005 |
| O'Reilly Consultancy Ltd | Financial services | 2020 |
| O'Sullivan Davies Ltd | Real estate | 2025 |
| O-Pawd Ltd | Health & social care | 2020 |
| O. & T.S. Catering Limited | Water & waste | 1989 |
| O.D Electrical (Bradford) Ltd | Construction | 2025 |
| O.Fit Ltd | Arts & recreation | 2022 |
| O.M.K. ENG. Consulting Ltd | Professional & scientific | 2023 |
| O.N Plumbing & Heating (Leeds) Ltd | Construction | 2024 |
| O.W. Pearson Consultancy Ltd | Professional & scientific | 2023 |
| O1 Insurance Services Ltd | Financial services | 2018 |
| O2 Anaesthesia Limited | Health & social care | 2011 |
| O7D Ltd | Wholesale & retail | 2024 |
| OA Rentals Ltd | Hospitality | 2021 |
| OAC Limited | Wholesale & retail | 2024 |
| OAD World Ltd | Financial services | 2024 |
| Oak & Acorn Properties Ltd | Other services | 2011 |
| Oak Blue Solutions Limited | Professional & scientific | 2015 |
| Oak Communications Ltd | Administrative & support | 2024 |
| Oak Court Management Limited | Households | 1986 |
| Oak Homes Leeds Limited | Real estate | 2025 |
| Oak Lodge (Harrogate) Maintenance Limited | Households | 1995 |
| Oak Park (Cookridge) Management Company Limited | Households | 2019 |
| Oak Park Gardens Management Company Limited | Real estate | 2018 |
| Oak Park Lettings Limited | Real estate | 2024 |
| Oak Properties (Northern) Limited | Real estate | 2004 |
| Oak Property Developments 2 Ltd | Real estate | 2020 |
| Oak Property Developments Ltd | Real estate | 2016 |
| Oak PROPERTY21 Ltd | Real estate | 2021 |
| Oak Smart Healthcare Ltd | Information & communication | 2024 |
| Oak Space Psychology Ltd | Education | 2023 |
| Oak Tree Court (York) Management Company Limited | Households | 2001 |
| Oak Tree Homes (Yorkshire) Limited | Real estate | 2002 |
| Oak Tree Technical Services Ltd | Information & communication | 2006 |
| Oakboat Properties Ltd. | Real estate | 2018 |
| Oakdene Interior Services Ltd | Construction | 2022 |
| Oakdene Interiors Ltd | Construction | 2017 |
| Oakdene Services Limited | Construction | 2006 |
| Oakenshaw Ltd | Administrative & support | 2023 |
| Oakfield House Management Company Limited | Households | 1994 |
| Oakfield Southern Services Ltd | Administrative & support | 2008 |
| Oakfresh Limited | Wholesale & retail | 2024 |
| Oakhampton Court Management Company Limited | Households | 1985 |
| Oakland Golf and Leisure Ltd | Administrative & support | 2009 |
| Oakland Group Services Limited | Administrative & support | 2019 |
| Oakland Interior Outlet Ltd | Wholesale & retail | 2026 |
| Oaklands (Robin Hood) Limited | Households | 1998 |
| Oaklands Construction Limited | Construction | 2011 |
| Oaklands Garage Ltd | Wholesale & retail | 2013 |
| Oaklands Heath Management Company Limited | Households | 2018 |
| Oaklands House Rodley Lane Management Company Limited | Households | 2005 |
| Oaklands Rest Home Limited | Administrative & support | 1992 |
| Oakleaf Environmental Ltd | Other services | 2016 |