| North Wright Property Group Ltd | Real estate | 2023 |
| Northcote Asset Management Ltd | Professional & scientific | 2019 |
| Norton House Management Limited | Households | 2008 |
| Notorious Online Limited | Professional & scientific | 2020 |
| Nova Darkroom Equipment Ltd | Professional & scientific | 1998 |
| Nova Recycling Solutions UK Ltd | Professional & scientific | 2020 |
| Nova RS Group Ltd | Extraterritorial | 2023 |
| NOVAS11 Limited | Wholesale & retail | 2020 |
| Noyes Orthopaedic Ltd | Health & social care | 2019 |
| NPS Home Joinery Ltd | Construction | 2024 |
| NR & PD Limited | Construction | 2026 |
| Nrds-Co Limited | Real estate | 2017 |
| NSB International Property Holdings Limited | Financial services | 2015 |
| NSR Developments Limited | Wholesale & retail | 2010 |
| Ntks Property Ltd | Real estate | 2024 |
| Number 3 CC Ltd | Hospitality | 2017 |
| NUMBER1 PAD Thai Ltd | Hospitality | 2025 |
| NUMBER39 Consulting Ltd | Information & communication | 2017 |
| Nuobello Entertainment Limited | Hospitality | 2013 |
| Nutcha Stratford Ltd | Health & social care | 2023 |
| Nutrition Matters Consultants Limited | Other services | 2025 |
| NY Twelve Limited | Wholesale & retail | 2019 |
| Nyetona Holding Group Limited | Financial services | 2019 |
| O'Brien (Group) Limited | Financial services | 2011 |
| O'Brien Developments Limited | Construction | 2011 |
| O2D Limited | Information & communication | 2024 |
| OAB Consulting Ltd | Professional & scientific | 2024 |
| OAH Services Ltd | Health & social care | 2021 |
| Oak Frame Design Ltd | Professional & scientific | 2025 |
| Oak Personal Training Ltd | Arts & recreation | 2025 |
| Oakbridge Technology Limited | Information & communication | 2025 |
| Oakwood Luxury Events Ltd | Hospitality | 2023 |
| Oatvale Ltd | Real estate | 2026 |
| OBM Management Limited | Professional & scientific | 2019 |
| Observer Properties Ltd | Real estate | 2020 |
| Ocassio Limited | Information & communication | 2005 |
| Occsys Ltd | Information & communication | 2007 |
| Oceania Properties Limited | Other services | 2004 |
| Oceanworld Limited | Hospitality | 2020 |
| Ocktcom Temporary Power Ltd | Administrative & support | 2013 |
| ODD JOB Property Services Ltd | Real estate | 2021 |
| Odda TEC Ltd | Information & communication | 2026 |
| Offc Ltd | Arts & recreation | 2009 |
| Office for Academic Support Ltd. | Professional & scientific | 2018 |
| Old Town Cottage Limited | Hospitality | 2015 |
| Old Tramway Revived CIC | Arts & recreation | 2020 |
| Oldmarketlofts Ltd | Real estate | 2021 |
| Olfacto Limited | Other services | 2019 |
| Oliver COX Consulting Limited | Administrative & support | 2016 |
| Oliver Hindley Photography Ltd | Professional & scientific | 2023 |
| Olly Murphy Racing Ltd | Agriculture & fishing | 2016 |
| OLO Creative Limited | Information & communication | 2009 |
| Olympus Healthcare Solutions Ltd | Health & social care | 2020 |
| OMG Racing Limited | Other services | 2017 |
| ON a Page Ltd | Professional & scientific | 2013 |
| ON the Vine Limited | Arts & recreation | 2023 |
| On-Line.P @ Per.Co.Uk Limited | Extraterritorial | 1999 |
| Onarvo Ltd | Administrative & support | 2026 |
| One Stop Haulage Ltd | Wholesale & retail | 2015 |
| One Woman Clothing Limited | Wholesale & retail | 2010 |
| Oneness Technical Solution Ltd | Professional & scientific | 2024 |
| ONO Aviation Limited | Transport & logistics | 2023 |
| Onpaper Shopping Limited | Wholesale & retail | 2023 |
| Onyx FOX Limited | Professional & scientific | 2022 |
| OP Services Ltd | Wholesale & retail | 2015 |
| Opera Identity Assurance Limited | Information & communication | 2019 |
| Optimae Innovations Limited | Manufacturing | 2024 |
| Optimum Worldwide Limited | Wholesale & retail | 2020 |
| Oracle Property Cleaning Ltd | Administrative & support | 2025 |
| Oracle Property Ltd | Real estate | 2021 |
| ORBITAL2 Ltd | Professional & scientific | 2003 |
| Orchard Meadow Developments Ltd | Real estate | 2022 |
| Orga Products Limited | Agriculture & fishing | 2000 |
| Oriental Massage Ltd | Other services | 2018 |
| Orpheus Properties Limited | Construction | 2020 |
| Orthogeni Ltd | Professional & scientific | 2019 |
| Osteria Dining Ltd | Hospitality | 2023 |
| Ostrava Property Limited | Extraterritorial | 2015 |
| Othello Automotive Limited | Wholesale & retail | 2020 |
| Othello Taxis LLP | | 2016 |
| Outcry Music Limited | Information & communication | 2017 |
| OV Pacific Ltd | Professional & scientific | 2022 |
| Overdrive Studios Ltd | Education | 2023 |
| Overflow Paints Specialists Limited | Construction | 2022 |
| OVI Cleaning Services Ltd | Administrative & support | 2025 |
| Oweb Photography Ltd | Professional & scientific | 2025 |
| OX Grills Limited | Manufacturing | 2015 |
| Oxbrdgrbtx Ltd | Professional & scientific | 2017 |
| Oxford Medical Writing Limited | Professional & scientific | 2004 |
| Oxleys Furniture Limited | Manufacturing | 1991 |
| P J M Surgical Limited | Health & social care | 2021 |
| P Wiltshire Limited | Professional & scientific | 2011 |
| P&A Management Investment Ltd | Professional & scientific | 2017 |
| P.J. Dawn Limited | Transport & logistics | 2003 |
| P.N.N Trans Ltd | Transport & logistics | 2018 |
| P2000 Ltd | Wholesale & retail | 2025 |
| Paddock Farm Butchery Ltd | Agriculture & fishing | 2015 |
| Paddock Mead (Snitterfield) Management Company Limited | Households | 2001 |
| Padel Traffic Solutions Ltd | Transport & logistics | 2024 |
| Pageant Graphics Limited | Wholesale & retail | 1983 |