| Olli Ella Limited | Administrative & support | 2010 |
| Ollo Financial Services Ltd | Financial services | 2021 |
| Olly Construct Ltd | Construction | 2024 |
| Olteanu H Ltd | Construction | 2023 |
| Olurotimi Ltd | Manufacturing | 2024 |
| Olympia Management Limited | Real estate | 2000 |
| Olympia Transport Limited | Transport & logistics | 2010 |
| Olympus Smile Services Ltd | Health & social care | 2021 |
| OM Bikes Limited | Administrative & support | 2021 |
| OM Bikes Rental Limited | Wholesale & retail | 2026 |
| OM Bikes Services Limited | Wholesale & retail | 2023 |
| OM Developers Limited | Construction | 2018 |
| OM E-Commerce Ltd | Wholesale & retail | 2026 |
| OM Essential Trading Limited | Wholesale & retail | 2021 |
| OM Films Limited | Information & communication | 2020 |
| OM Funeral Care Ltd | Professional & scientific | 2018 |
| OM General Supplies Limited | Wholesale & retail | 2018 |
| OM Investment Management Limited | Real estate | 2016 |
| OM Laxmi Sairam Ltd | Hospitality | 2013 |
| OM Properties & Investments Ltd | Real estate | 2025 |
| OM SAI Construction Limited | Construction | 2007 |
| OM SAI RAM Brit Ltd | Transport & logistics | 2022 |
| OM SAI RAM Travel Ltd | Administrative & support | 2024 |
| OM SAI Retail Shops Ltd | Wholesale & retail | 2018 |
| OM Shanti Funeral Services Limited | Other services | 2022 |
| OM Shiva Shakti Ltd | Other services | 2021 |
| OM Synergy Space Link Limited | Real estate | 2022 |
| Omar Khan Limited | Information & communication | 2012 |
| Omar Shaaban Consultancy Services Limited | Hospitality | 2019 |
| Ombeck Diagnostics Ltd | Health & social care | 2025 |
| Ombeda Investment Ltd | Construction | 2025 |
| Omcare Education Ltd | Health & social care | 2025 |
| Omega Drives & Patios Limited | Administrative & support | 2022 |
| Omega Driveways Limited | Administrative & support | 2025 |
| Omega Health and Wellness Clinic Ltd | Health & social care | 2022 |
| Omega Leisure Management Limited | Transport & logistics | 1996 |
| Omega Packages Ltd | Wholesale & retail | 2025 |
| Omega Rentals Oxford Ltd | Administrative & support | 2024 |
| Omfs Services Limited | Health & social care | 2023 |
| Omkar Creations Ltd | Wholesale & retail | 2021 |
| Omkar Technologies Ltd | Information & communication | 2011 |
| Omkar Traders Ltd | Wholesale & retail | 2024 |
| Omkara Trading Limited | Wholesale & retail | 2020 |
| Omko Ltd | Construction | 2025 |
| OMMA24 Ltd | Health & social care | 2024 |
| Omni Athletica Limited | Health & social care | 2025 |
| Omni Trading Solutions Ltd | Construction | 2025 |
| Omnia Search & Selection Limited | Administrative & support | 2021 |
| Omnicom Trading LLP | | 2010 |
| Omnicx Digital Limited | Information & communication | 2015 |
| Omnify Ltd | Wholesale & retail | 2026 |
| Omnilert Systems Ltd | Administrative & support | 2021 |
| Omniloop Ltd | Wholesale & retail | 2026 |
| Omnistream Limited | Real estate | 2006 |
| Omnivita Limited | Administrative & support | 2010 |
| Omniya AAS Limited | Financial services | 2021 |
| Omniya DK Limited | Financial services | 2021 |
| Omniya Holdings Limited | Financial services | 2016 |
| Omniya Limited | Health & social care | 2014 |
| Omnp Ltd | Professional & scientific | 2022 |
| Omovendz Ltd | Wholesale & retail | 2025 |
| Omps Consulting Limited | Other services | 2015 |
| OMS Estates Ltd | Real estate | 2020 |
| ON Call Secure Ltd | Administrative & support | 2025 |
| ON Premises Laundry Limited | Administrative & support | 1991 |
| ON the BAB Europe Limited | Hospitality | 2017 |
| ON the BAB FT Limited | Extraterritorial | 2016 |
| ON the BAB Limited | Extraterritorial | 2016 |
| ON the Curb Real Estate Ltd | Information & communication | 2025 |
| ON the Rise Estates Limited | Real estate | 2025 |
| ON Tour Travels Ltd | Administrative & support | 2025 |
| On-Track Marketing Limited | Professional & scientific | 2024 |
| On-U Sound Records and Music Limited | Information & communication | 1983 |
| Onashi Trading Co Limited | Professional & scientific | 2025 |
| Onbits Global Limited | Water & waste | 2022 |
| ONC Construction Ltd | Construction | 2022 |
| Oncommittment Limited | Professional & scientific | 2024 |
| One Binary Connect Ltd | Information & communication | 2017 |
| One Brick at a Time Ltd | Real estate | 2011 |
| One Broadway Management Limited | Hospitality | 2019 |
| One Centaur Street Management Company Limited | Households | 2004 |
| One DOT Media Limited | Other services | 2020 |
| One Durham Road Limited | Professional & scientific | 2015 |
| One Dynamics Ltd | Information & communication | 2019 |
| One Easy Stop Limited | Financial services | 2017 |
| One Eleven Ltd | Hospitality | 2020 |
| One Elysium Ltd | Hospitality | 2023 |
| One Football Academy CIC | Arts & recreation | 2026 |
| One Globe Studio Ltd | Professional & scientific | 2015 |
| One Green Nature UK Limited | Education | 2026 |
| One Health Digital Imaging Limited | Information & communication | 2024 |
| One Holland Park Gardens Limited | Real estate | 2022 |
| One House United Ltd | Real estate | 2024 |
| One Hub PVT Ltd | Hospitality | 2023 |
| One Infinite Limited | Information & communication | 2014 |
| One Life Realty Ltd | Real estate | 2017 |
| One MCG Consulting Limited | Information & communication | 2016 |
| One Media Consulting Ltd. | Other services | 2016 |
| One Ocean Labs Limited | Information & communication | 2019 |
| One Point Assistants Ltd | Administrative & support | 2018 |