| Nudl Enterprises Limited | Hospitality | 2019 |
| Nuestra Familia Restaurants Ltd | Hospitality | 2013 |
| Nugent Pump Services Ltd | Construction | 2020 |
| Numero UNO OG Ltd | Hospitality | 2026 |
| Nuspe Ltd | Real estate | 2024 |
| Nutshaw Kennels & Cattery Limited | Agriculture & fishing | 2009 |
| NW Compliance Ltd | Professional & scientific | 2025 |
| NW Groundwork & Civil Engineering Limited | Construction | 2017 |
| NW IT Solutions Ltd | Information & communication | 2009 |
| NW Power Solutions Limited | Construction | 2024 |
| Nwbc Limited | Professional & scientific | 2015 |
| Nwir Investments Limited | Financial services | 2000 |
| NWK Brothers Ltd | Real estate | 2024 |
| NWL Tyres Limited | Wholesale & retail | 2024 |
| NWP Plumbing Limited | Construction | 2021 |
| NWP Wholesale Ltd | Construction | 2017 |
| NWR Properties Limited | Real estate | 2012 |
| NWR GAS, Plumbing & Heating Ltd | Construction | 2021 |
| NY Aesthetics Ltd | Health & social care | 2018 |
| NZ Clouds Network Ltd | Information & communication | 2020 |
| O Y Portfolios Ltd | Real estate | 2026 |
| O'Neill Building Contractors Ltd | Construction | 2019 |
| O.Fury Electrical Solutions Limited | Construction | 2015 |
| Oak Trees Leisure Ltd | Real estate | 2010 |
| Oakdene Estates Ltd | Construction | 2005 |
| Oakedge Aquisition Ltd | Real estate | 2021 |
| Oakwood Psychology Services | Health & social care | 2014 |
| Obsoft Tech Solutions Ltd | Information & communication | 2025 |
| OC1 Project Ltd | Construction | 2019 |
| Ocean Ltd | Financial services | 2005 |
| Ocean Planet Limited | Wholesale & retail | 2020 |
| Oceanfield Ltd | Wholesale & retail | 2025 |
| Oceanic Organic Ltd | Agriculture & fishing | 2023 |
| Ocolen Ltd | Extraterritorial | 2011 |
| OFF Road Action Limited | Extraterritorial | 2020 |
| OGM Holding Ltd | Financial services | 2026 |
| OHM Recruitment Limited | Administrative & support | 2014 |
| Oivg Ltd | Financial services | 2025 |
| OJS Housing Ltd | Real estate | 2023 |
| Okep Ltd | Construction | 2017 |
| Oksaneta Transport Limited | Transport & logistics | 2017 |
| Olive High Boys Ltd | Education | 2022 |
| Olive High Ltd | Education | 2016 |
| Olive Mount Preparatory Ltd | Education | 2026 |
| Olive Tree Nursery Ltd | Education | 2014 |
| Oliver John Kitchens & Granite Limited | Wholesale & retail | 2010 |
| Oliver’S Automotive Ltd | Transport & logistics | 2025 |
| Olliver Charles Ltd | Administrative & support | 2020 |
| Ollycom Ltd | Information & communication | 2011 |
| OM SAI International Ltd | Hospitality | 2018 |
| Omni Heat and Power Limited | Manufacturing | 2015 |
| ON Track Deliveries Ltd | Other services | 2021 |
| Onboard Vehicle Tech Ltd | Wholesale & retail | 2024 |
| ONBRAND4U Ltd | Manufacturing | 2019 |
| One Bargain Ltd | Wholesale & retail | 2026 |
| One Shop Appliances Ltd | Wholesale & retail | 2025 |
| One Stop Digital Agency Limited | Information & communication | 2016 |
| One-On Limited | Construction | 2009 |
| Onefolio Ltd | Information & communication | 2025 |
| Onlynourish Ltd | Hospitality | 2025 |
| Onpoint Metal Limited | Manufacturing | 2025 |
| Open Door Furniture Recycling Limited | Water & waste | 2004 |
| Open Promotions Limited | Information & communication | 2014 |
| Openshore Property Limited | Real estate | 2007 |
| Operator Licence Ltd | Professional & scientific | 2026 |
| Ophardt Product (UK) Limited | Wholesale & retail | 1977 |
| Opies RAW Dog Food and Natural Treats Ltd | Other services | 2026 |
| Optima (GB) Limited | Professional & scientific | 2008 |
| Optima GB Estates Ltd | Real estate | 2010 |
| Optima Medical Reports Limited | Other services | 2009 |
| Optimal Hydration Limited | Manufacturing | 2023 |
| Optimus Support Ltd | Construction | 2017 |
| Option D Coaching Ltd | Professional & scientific | 2015 |
| Optisec-Cs Ltd | Professional & scientific | 2025 |
| Opulean Ltd | Administrative & support | 2024 |
| Opus Audio Visual Ltd | Professional & scientific | 2021 |
| Opus Broadband Topco Limited | Financial services | 2024 |
| Opus Group Developments Ltd | Construction | 2023 |
| Opus Pro Audio Limited | Construction | 2007 |
| Opus Support Services Limited | Administrative & support | 2024 |
| Oracle Essence Ltd | Wholesale & retail | 2025 |
| Orange Street Limited | Arts & recreation | 2016 |
| Oravita Ltd | Health & social care | 2025 |
| Orbis Sports Management Ltd | Professional & scientific | 2024 |
| Orbistore Limited | Wholesale & retail | 2022 |
| Orchard Strength & Performance Ltd | Health & social care | 2026 |
| Order in Solutions Ltd | Professional & scientific | 2023 |
| Orhan Travels Limited | Transport & logistics | 2025 |
| Original Green Ltd | Wholesale & retail | 2014 |
| Ormcliffe Ltd | Extraterritorial | 2015 |
| Orme Court Management Limited | Real estate | 2017 |
| Ornament of Grace Investment Limited | Wholesale & retail | 2023 |
| Oros Aerospace Ltd | Manufacturing | 2017 |
| Orrell Group Engineering Limited | Wholesale & retail | 2019 |
| Orrell Group Plant Limited | Wholesale & retail | 2019 |
| Orthodontic Health Limited | Health & social care | 2014 |
| Oryntis Limited | Wholesale & retail | 2025 |
| Oryx - Office & Fitted Furniture Installations Ltd | Construction | 2015 |
| OS Generation Limited | Energy | 2018 |
| Osama Khalid E-Shop-Elite Ltd | Wholesale & retail | 2025 |