| Ocho Properties Ltd | Real estate | 2024 |
| Ochre Consulting Ltd | Professional & scientific | 2009 |
| OCM U.K. Limited | Wholesale & retail | 2021 |
| OCN GAS & Plumbing Services Ltd | Construction | 2022 |
| Ocnh Limited | Real estate | 2022 |
| OCP Property Ltd | Real estate | 2022 |
| OCP Site Solutions Ltd | Professional & scientific | 2023 |
| Octagon Entertainment Limited | Transport & logistics | 2007 |
| Octagon Green Solutions Limited | Water & waste | 2012 |
| Octagon Ímmo Pro Ltd. | Financial services | 2017 |
| Octal Computing (UK) Ltd | Information & communication | 2019 |
| Octane Supplements Ltd | Manufacturing | 2025 |
| Octave Limited | Professional & scientific | 2003 |
| Octavia Chelsea Limited | Real estate | 2012 |
| Octavia Learning Ltd | Professional & scientific | 2020 |
| Octigan Psychology Limited | Education | 2025 |
| Octo Properties Ltd | Real estate | 2020 |
| Octofloor Limited | Construction | 2024 |
| Octogon Properties Ltd | Real estate | 2026 |
| Octogon Solutions Ltd | Administrative & support | 2016 |
| Octopath LLP | | 2025 |
| Octopus Building Services Limited | Construction | 2008 |
| Octopus Inc Holdings Limited | Financial services | 2025 |
| Octopus Residential Limited | Real estate | 2007 |
| Octopus Waterproofing Services Ltd | Construction | 2019 |
| Octra Ltd | Wholesale & retail | 2019 |
| Ocuflow Ltd | Manufacturing | 2020 |
| Oculamor Ltd | Professional & scientific | 2026 |
| Oculis Construction Consultants Ltd | Professional & scientific | 2018 |
| Ocyt 3 Limited | Professional & scientific | 1945 |
| Odabas Foods Limited | Hospitality | 2024 |
| Odabas Property Ltd | Real estate | 2024 |
| Odale Limited | Professional & scientific | 2007 |
| ODD Bike Community Interest Company | Wholesale & retail | 2021 |
| ODD JOB Heroes Limited | Construction | 2022 |
| Odda Recordings Ltd | Information & communication | 2022 |
| Oddly Groovy Limited | Wholesale & retail | 2024 |
| Oddlyyours Ltd | Wholesale & retail | 2025 |
| Oddy & Co Limited | Professional & scientific | 2011 |
| Oddy Hydraulics Limited | Manufacturing | 1985 |
| ODF Medical Ltd | Health & social care | 2024 |
| ODG Commercial Limited | Hospitality | 2024 |
| ODG Holdings Limited | Financial services | 2023 |
| ODH Interiors Ltd | Construction | 2024 |
| Odin's EYE Consulting Limited | Extraterritorial | 2025 |
| Odinma Limited | Information & communication | 2009 |
| Odkzimri Medical Ltd | Wholesale & retail | 2025 |
| ODL Realisations (2025) Limited | Hospitality | 2022 |
| ODO Trans Ltd | Transport & logistics | 2019 |
| ODP Contracting Ltd | Administrative & support | 2013 |
| Odray Ltd | Other services | 2013 |
| Odus Transportation and Logistics Services Limited | Transport & logistics | 2025 |
| Odyssean Strategy Ltd | Professional & scientific | 2025 |
| Odyssey MM Group Ltd | Professional & scientific | 2021 |
| Odyssia Holdings 3 Limited | Professional & scientific | 2025 |
| Odyssia Ltd | Professional & scientific | 2019 |
| OEC Consulting Engineers Ltd | Professional & scientific | 2017 |
| Oecas Ltd | Wholesale & retail | 2023 |
| OEM Car Audio Ltd | Wholesale & retail | 2011 |
| OEM+ Customz Limited | Wholesale & retail | 2026 |
| OEP Property Ventures Limited | Real estate | 2021 |
| OF the Wildside Ltd | Arts & recreation | 2022 |
| Ofch Property Development Limited | Real estate | 2026 |
| OFF Piste Performance Limited | Arts & recreation | 2011 |
| OFF the Shelf Marketing Limited | Professional & scientific | 2022 |
| OFF the TEE Golf Ltd | Information & communication | 2026 |
| OFF West END Limited | Real estate | 2021 |
| Office 1ST Limited | Wholesale & retail | 2009 |
| Office Design & Project Services Limited | Construction | 2003 |
| Office Essentials 4 YOU Limited | Wholesale & retail | 2025 |
| Office Furniture Experts Ltd | Wholesale & retail | 2021 |
| Office Furniture Supplies Limited | Other services | 2018 |
| Office Monster Limited | Wholesale & retail | 2014 |
| Office Odyssey Limited | Administrative & support | 2018 |
| OFFICE42 Services Ltd | Information & communication | 2016 |
| Officeteam Group Limited | Professional & scientific | 2004 |
| Officeteam Limited | Wholesale & retail | 2004 |
| Official Entertainment Limited | Arts & recreation | 2024 |
| Official Jeweller Ltd | Extraterritorial | 2015 |
| Offload 1 Limited | Administrative & support | 2019 |
| Offlow Haulage Ltd | Transport & logistics | 2018 |
| Offploy C.I.C. | Information & communication | 2016 |
| Offshore Drafting Services Limited | Professional & scientific | 2002 |
| Offsum Ltd | Wholesale & retail | 2019 |
| Ofki Limited | Real estate | 2020 |
| Ofono Ltd | Information & communication | 2017 |
| Ofor Ltd | Wholesale & retail | 2025 |
| Oforiwaa Healthcare Ltd | Administrative & support | 2016 |
| Ofosua African Supermarket Ltd | Other services | 2022 |
| OGA Ventures Limited | Real estate | 2011 |
| Ogden Engineering Limited | Extraterritorial | 1949 |
| Ogden Transport Limited | Extraterritorial | 1959 |
| Ogden Yorkstone Limited | Extraterritorial | 1964 |
| Oggle Blox Ltd | Households | 2025 |
| Oggle Professional Services Ltd | Administrative & support | 2025 |
| Ogilvy FM Limited | Manufacturing | 2020 |
| Oginni Properties Ltd | Real estate | 2025 |
| OH Fantastic Ltd | Other services | 2020 |
| OH Piling Limited | Construction | 2019 |
| OH! Moru Garden Limited | Wholesale & retail | 2025 |