| O.T.T Brand Ltd | Wholesale & retail | 2023 |
| OA Collective Limited | Administrative & support | 2025 |
| Oaer Properties Limited | Real estate | 2025 |
| Oak Farm Rentals Limited | Real estate | 2026 |
| Oak Motors (Kent) Ltd | Wholesale & retail | 2012 |
| Oak Processionary Moth Ltd | Extraterritorial | 2011 |
| Oakhaven Properties Limited | Real estate | 2021 |
| Oakhurst Court Management RTM Company Limited | Households | 2016 |
| Oakley Renewable Solutions Limited | Energy | 2023 |
| Oakmon's Recovery Ltd | Transport & logistics | 2026 |
| Oaks Hamlet Management Company Limited | Households | 2007 |
| Oaks QS Ltd | Construction | 2013 |
| Oakstone Property Services Ltd | Administrative & support | 2026 |
| Oaksys Ltd | Wholesale & retail | 2024 |
| Oakwater Carpentry Contractors Ltd | Construction | 2025 |
| Oakwood Heights (Maidstone) Management Company Limited | Households | 2012 |
| Oakwood Place Management Company Maidstone Limited | Households | 2002 |
| Oasis Carnival Club Limited | Other services | 2004 |
| Oasis Homes and Properties Limited | Real estate | 2024 |
| OB Events Limited | Construction | 2017 |
| Obiiuto Evas Limited | Health & social care | 2018 |
| Oceanrise Healthcare Agency Ltd | Other services | 2010 |
| Oceans Green DRY Cleaners Limited | Other services | 2018 |
| Octave Mechanical Services Limited | Energy | 2019 |
| Ocular Event & Security Management Ltd | Administrative & support | 2024 |
| Odaan Investment Properties Ltd | Real estate | 2025 |
| ODM Seeds, Tithes & Gifts Ltd | Information & communication | 2015 |
| Odrey Investment Company Ltd | Extraterritorial | 2025 |
| ODT Logistics Ltd | Transport & logistics | 2022 |
| Odybill Services Limited | Information & communication | 2013 |
| Oelmil Ltd | Health & social care | 2010 |
| Ofaya Decor Ltd | Wholesale & retail | 2020 |
| Ofinis Limited | Information & communication | 2026 |
| Oggy Construction Ltd | Construction | 2023 |
| Oguta UK & Ireland Asso Ltd | Other services | 2021 |
| Ogutlu Rails Ltd | Construction | 2025 |
| OHM Facilities Limited | Administrative & support | 2017 |
| Ohsh Projects Ltd | Arts & recreation | 2025 |
| Okelite Services Ltd | Construction | 2023 |
| Oklanc Ltd | Wholesale & retail | 2023 |
| Olaris Limited | Real estate | 2025 |
| Old Tannery Works Ltd | Real estate | 2021 |
| Olivbells Creations Limited | Manufacturing | 2017 |
| Olive Electrical Ltd | Energy | 2021 |
| Olive Lane Property Limited | Real estate | 2024 |
| Olive Ware Ltd | Information & communication | 2019 |
| Oluwabamise Enterprise Ltd | Other services | 2017 |
| Omega Care UK Limited | Health & social care | 2021 |
| Omega Consulting Services Limited | Professional & scientific | 2008 |
| Omega Geomatics Ltd | Administrative & support | 2009 |
| Omega IT Group Ltd | Wholesale & retail | 2017 |
| Omega Property Holdings Limited | Real estate | 2017 |
| Omega WSR Property Ltd | Real estate | 2021 |
| Omnicroft Limited | Households | 2007 |
| Omnitech Group Ltd | Professional & scientific | 2025 |
| OMO Aresa Incorp Limited | Wholesale & retail | 2025 |
| Omotie Solutions Limited | Professional & scientific | 2018 |
| Omral Solutions Ltd | Wholesale & retail | 2026 |
| ON Line Vape Ltd | Wholesale & retail | 2018 |
| ON SET Security Ltd | Administrative & support | 2018 |
| ONA Medical Aesthetic Ltd | Health & social care | 2026 |
| Oncall Appliances Ltd | Other services | 2019 |
| One Box Ltd | Hospitality | 2020 |
| One Status Ltd | Wholesale & retail | 2020 |
| ONE2ONE Locksmiths Limited | Construction | 2015 |
| Oneness Property Solution Ltd | Professional & scientific | 2026 |
| Ones Electrical Services Ltd | Construction | 2021 |
| Onkaar Houseware Ltd | Wholesale & retail | 2019 |
| Only BE Ltd | Health & social care | 2024 |
| Onodi Automotive Limited | Wholesale & retail | 2022 |
| Onodi Car Sales Limited | Wholesale & retail | 2016 |
| Onwards & Upwards Scaffolding Limited | Construction | 2006 |
| Onyx EYE Ltd | Financial services | 2025 |
| Onyx RSL Limited | Wholesale & retail | 2017 |
| Opalon Plastic Packing Co., Ltd | Manufacturing | 2022 |
| Open Matz Ltd | Arts & recreation | 2023 |
| Opera ETC Limited | Arts & recreation | 2010 |
| Operation GAS Ltd | Construction | 2020 |
| Operator Compliance South East Ltd | Transport & logistics | 2012 |
| Opsy Capital Limited | Administrative & support | 2019 |
| Opti Wash Limited | Other services | 2024 |
| Optiaiuk Ltd | Information & communication | 2026 |
| Optima Electrical Solutions Ltd | Construction | 2024 |
| Optimalplus Hair and Beauty Limited | Wholesale & retail | 2020 |
| Optimum Compassionate Care Limited | Health & social care | 2026 |
| Options Adult Daycare Limited | Health & social care | 2018 |
| Optiwindows Ltd. | Construction | 2017 |
| Orbis Moving Ltd | Transport & logistics | 2016 |
| Organise Hub Ltd | Professional & scientific | 2024 |
| Orientai Flourish Group Ltd | Manufacturing | 2023 |
| Oriental Fuda Trade Co., Ltd | Extraterritorial | 2023 |
| Oriental Industrial Solution Ltd | Manufacturing | 2020 |
| Oriental Packaging Solution Ltd | Manufacturing | 2019 |
| Origin Fibre Ltd | Information & communication | 2023 |
| Origin MMA Ltd | Arts & recreation | 2026 |
| Orion Supported Learning Ltd | Education | 2023 |
| Orochi Arts Ltd | Administrative & support | 2023 |
| Orotech Ltd | Information & communication | 2026 |
| Orris Home Limited | Manufacturing | 2025 |
| Osborn & Osborn Ltd | Professional & scientific | 2012 |