| NV Luxury Style Ltd | Construction | 2025 |
| Nwambaise Limited | Health & social care | 2021 |
| NX Growth Limited | Administrative & support | 2024 |
| NXS Intelligence Ltd | Information & communication | 2026 |
| Nyamekye Cameras and Deals Ltd | Wholesale & retail | 2025 |
| Nyamz Limited | Hospitality | 2018 |
| O R Aroma Ltd | Wholesale & retail | 2021 |
| O&A Trading Ltd | Transport & logistics | 2023 |
| O&F Pasha Limited | Hospitality | 2022 |
| O&M Contracts Ltd | Construction | 2024 |
| O'Connor Holiday Leisure Ltd | Hospitality | 2026 |
| O'Reilly Builders Limited | Construction | 2013 |
| O.C. Holdings (UK) Limited | Real estate | 2012 |
| O.C.M Maintenance Management Ltd | Other services | 2014 |
| O.J Ventures Ltd | Health & social care | 2017 |
| Oak & Olive Gardens Limited | Administrative & support | 2025 |
| Oakelm Developments LLP | | 2022 |
| Oakelm Homes Limited | Construction | 2020 |
| Oaklands Manor Limited | Real estate | 2017 |
| Oasis Residence Ltd | Real estate | 2020 |
| Oats and Rice Ltd | Wholesale & retail | 2016 |
| OB Promotions Ltd | Education | 2025 |
| Occupational Health Chambers Ltd | Other services | 2015 |
| Occupied Limited | Real estate | 2019 |
| Ocset Investments Limited | Real estate | 2024 |
| Oculus Vision Limited | Health & social care | 2022 |
| OD Accountancy Practice Ltd | Professional & scientific | 2017 |
| Odee Property Ltd | Real estate | 2022 |
| Odin Guard Services Ltd | Extraterritorial | 2024 |
| Odyssean Security Limited | Administrative & support | 2024 |
| OED Contractors Ltd | Construction | 2021 |
| OF Medical Ltd | Health & social care | 2023 |
| Office Space Near ME Ltd | Information & communication | 2020 |
| Ogan Ltd | Wholesale & retail | 2018 |
| Ogec Ltd | Wholesale & retail | 2018 |
| Ogori Magic Limited | Professional & scientific | 2015 |
| Ogutu Medical Ltd. | Health & social care | 2013 |
| Oharrocraft Carpentry Ltd | Manufacturing | 2025 |
| Oheneba Operations Limited | Administrative & support | 2024 |
| Ohio Holdings Ltd | Real estate | 2023 |
| Ojey Consultancy Limited | Administrative & support | 2014 |
| OJI Homes Ltd | Real estate | 2024 |
| OK Consulting & Investment Ltd | Professional & scientific | 2022 |
| Okai Limited | Information & communication | 2025 |
| OKE Systems Investment Limited | Real estate | 2021 |
| OKE Systems Limited | Real estate | 2025 |
| Okesystems Consulting Limited | Information & communication | 2013 |
| Olant Limited | Construction | 2014 |
| Olas Security Service Ltd | Financial services | 2021 |
| Olive Gold Care Services Ltd | Health & social care | 2024 |
| Oliver Maughan Engineering Limited | Administrative & support | 2023 |
| Oliver's Tutoring Ltd | Education | 2022 |
| Olivia Somary Limited | Hospitality | 2023 |
| Olivier Deli 1 Limited | Extraterritorial | 2021 |
| Olivier Delicatessen Ltd | Hospitality | 2016 |
| Ollycare Ltd | Financial services | 2024 |
| Omberan Limited | Wholesale & retail | 2025 |
| OMZ Property Limited | Real estate | 2024 |
| ON Screen LLP | | 2011 |
| ON the JOB Waste Management Ltd | Water & waste | 2025 |
| One 03 Ltd | Real estate | 2025 |
| One Arch Ltd | Construction | 2022 |
| One Brandy Limited | Wholesale & retail | 2024 |
| One Pond Sell Ltd | Administrative & support | 2025 |
| One Potato Games Limited | Manufacturing | 2019 |
| One Small Cube Limited | Other services | 2025 |
| One to Four Brentford LLP | | 2022 |
| Onguard Waste Removal Logistics Ltd | Water & waste | 2025 |
| Only Tans World Limited | Other services | 2023 |
| Onslow Projects Ltd | Construction | 2023 |
| Onyx 12 Limited | Real estate | 2025 |
| Opal and Iris Limited | Wholesale & retail | 2026 |
| Opes Investments Ltd | Administrative & support | 2021 |
| Opps Evolution Ltd | Professional & scientific | 2016 |
| Optical Stylists Ltd | Wholesale & retail | 2024 |
| Optimal Plumbing Limited | Construction | 2026 |
| Optimum Food Centre Ltd | Wholesale & retail | 2013 |
| Optimus Automations Ltd | Manufacturing | 2018 |
| Options for Homes Limited | Real estate | 2013 |
| Opulence Motors Ltd | Wholesale & retail | 2018 |
| ORC Design and Print Ltd | Manufacturing | 2016 |
| Orcas Informatica Limited | Information & communication | 2019 |
| Orderuk Limited | Hospitality | 2024 |
| Orhan and Bilge Property Ltd | Real estate | 2023 |
| Oriental WOK (2016) Ltd | Hospitality | 2016 |
| Orlando Accountancy Limited | Professional & scientific | 2014 |
| Orman Imperials Ltd | Hospitality | 2025 |
| Ornate Marketing Limited | Information & communication | 2022 |
| Oromtomas Ltd | Construction | 2026 |
| ORT Lifts Ltd | Manufacturing | 2026 |
| Ortak TAT Ltd | Wholesale & retail | 2015 |
| OS Construction Creators Limited | Construction | 2024 |
| Osanu & Son's Ltd | Construction | 2025 |
| Osborne Partnership | Other services | 1997 |
| Oslo Court Garage Limited | Wholesale & retail | 2016 |
| Ossie Cuts Ltd | Other services | 2024 |
| Otseh Taiwo Properties Limited | Real estate | 2025 |
| OTT Health&Beauty Ltd | Wholesale & retail | 2025 |
| Otter Minds Limited | Wholesale & retail | 2024 |
| OUM Tribe Limited | Health & social care | 2024 |