| Ockbrook Properties Limited | Real estate | 2017 |
| Oconnor Electrical Limited | Construction | 1992 |
| Oconnor Security Ltd | Professional & scientific | 2009 |
| Ocons Limited | Information & communication | 2020 |
| Octo Vitae Property Management Ltd | Real estate | 2023 |
| Octrax Holdings Limited | Wholesale & retail | 2017 |
| Ocupi Ltd | Real estate | 2025 |
| Odeam Properties Ltd | Real estate | 2024 |
| Odedra Store Ltd | Wholesale & retail | 2025 |
| Odessa Cairns Limited | Professional & scientific | 2013 |
| Odont Ltd | Professional & scientific | 2025 |
| Odrb Limited | Financial services | 2010 |
| Odriscoll Holdings Ltd | Education | 2025 |
| Odyssey Collaborative Trust | Education | 2018 |
| OFF Road Skills Limited | Arts & recreation | 2001 |
| OFF the Hook (MLL) Ltd | Information & communication | 2023 |
| Office Care Limited | Administrative & support | 2005 |
| Office Elite Limited | Information & communication | 2025 |
| Office Oasis Limited | Administrative & support | 2003 |
| OFFICE24X7 LLP | | 2019 |
| OFFICE24X7 Services Ltd | Wholesale & retail | 2023 |
| Officers Global Limited | Real estate | 2022 |
| Offices.Co.Uk Serviced Offices Limited | Real estate | 2009 |
| Offpayroll.Org.Uk Ltd | Information & communication | 2020 |
| Ogara Studios Ltd | Manufacturing | 2020 |
| OH Cars Ltd | Wholesale & retail | 2025 |
| OHI Landmarks Limited | Real estate | 2025 |
| Oiysis Properties Limited | Real estate | 2022 |
| OJJ Properties Ltd | Real estate | 2023 |
| Ojstanley Ltd | Information & communication | 2017 |
| OK 8BT Limited | Hospitality | 2018 |
| Okaeri Holdings Ltd | Financial services | 2022 |
| Okement Digital Health Limited | Information & communication | 2026 |
| Okra Curry House Ltd | Hospitality | 2026 |
| Oladex Engineering and Servicing Limited | Manufacturing | 2023 |
| Olah David Services Ltd | Transport & logistics | 2024 |
| Olax Property Ltd | Real estate | 2025 |
| Old 20 Parts Co Limited | Professional & scientific | 1999 |
| Old Chapel Estates Ltd | Real estate | 2019 |
| Old Chicken Farm Limited | Wholesale & retail | 2014 |
| Old Hall (Derby) Ltd | Wholesale & retail | 2015 |
| Old Hall Farm Derby Ltd | Real estate | 2025 |
| Old Oak Limited | Real estate | 2024 |
| Old Port Trading Ltd | Hospitality | 2026 |
| Old Road Store Derby Limited | Wholesale & retail | 2025 |
| Old School House Derby Limited | Construction | 2025 |
| Old School House Developments Derby Limited | Construction | 2025 |
| Old Stable Wellness Limited | Arts & recreation | 2018 |
| Old Talbot Hilton Ltd | Hospitality | 2026 |
| Old Tower Properties Limited | Real estate | 2024 |
| Oldacres Investments Limited | Financial services | 2025 |
| Olders Valley Limited | Real estate | 2004 |
| Oldfield Management Company (Derby) Limited | Households | 2026 |
| Oldhills Farm Ltd | Construction | 2021 |
| Olea Consulting Limited | Professional & scientific | 2022 |
| Olinco Services Limited | Health & social care | 2016 |
| Oliv-Harr House Limited | Real estate | 2026 |
| Olivant and Rains Limited | Professional & scientific | 1947 |
| Olive Nook Living Spaces Ltd | Hospitality | 2025 |
| Olive Oak Ltd | Health & social care | 2025 |
| Olive Stays Limited | Real estate | 2020 |
| Olive Tree Developments Limited | Real estate | 2003 |
| Olive Tree Roofing Limited | Construction | 2025 |
| OLIVE24 Healthcare Ltd | Health & social care | 2025 |
| Oliver Construction & Carpentry Ltd | Manufacturing | 2024 |
| Oliver Holloway Limited | Financial services | 2007 |
| Oliver J Tattoo Ltd | Arts & recreation | 2023 |
| Oliverose Construction Limited | Construction | 2015 |
| Olivers Events Limited | Arts & recreation | 2022 |
| Olivers Holdings Limited | Financial services | 2020 |
| Ollen Ltd | Wholesale & retail | 2018 |
| Ollybee Limited | Wholesale & retail | 2025 |
| Ollybia Ltd | Hospitality | 2018 |
| Olori Essence Global Limited | Wholesale & retail | 2025 |
| Olrems Limited | Health & social care | 2025 |
| Olte Property Maintenance Ltd | Construction | 2019 |
| Oltre Fmcg Limited | Professional & scientific | 2018 |
| Olvic Trans Ltd | Transport & logistics | 2017 |
| Olympus Media Limited | Professional & scientific | 2021 |
| OM Derby Limited | Wholesale & retail | 2021 |
| Omaeva Ltd | Information & communication | 2023 |
| Omega IT Services Limited | Information & communication | 2002 |
| Omega Logistics Ltd | Other services | 2006 |
| Omegas Enterprises Limited | Professional & scientific | 2018 |
| Omni Cater Ltd | Hospitality | 2024 |
| Omni Estates Limited | Real estate | 1980 |
| Omniclean Services Limited | Administrative & support | 2025 |
| Omnisco Holdings Ltd | Financial services | 2022 |
| Omnisco Investments Ltd | Financial services | 2022 |
| Omnitrade Limited | Extraterritorial | 2024 |
| Omnitrend Systems Ltd | Wholesale & retail | 2026 |
| ON Brand Clothing Ltd | Wholesale & retail | 2024 |
| ON Consulting Limited | Professional & scientific | 2023 |
| ON House Signs Ltd | Administrative & support | 2016 |
| ON My Level Ltd | Wholesale & retail | 2025 |
| ON Point Apartment Services Ltd | Administrative & support | 2023 |
| ON TAP Heating Ltd | Construction | 2022 |
| ON Tick Ltd | Administrative & support | 2020 |
| ON Track Design Solutions Limited | Professional & scientific | 2004 |
| ON With the Sparkle Ltd | Other services | 2021 |