| ON Call Select Ltd | Information & communication | 2025 |
| ON Point MOT Ltd | Wholesale & retail | 2018 |
| ON Point Projects Limited | Manufacturing | 2016 |
| ON Purpose Design Limited | Administrative & support | 2004 |
| ON Site Services (Calibration) Limited | Professional & scientific | 2002 |
| ON Target Sales Consultancy Limited | Other services | 2018 |
| ON the Ball Coaching Ltd | Education | 2007 |
| ON the Case Mysteries Limited | Wholesale & retail | 2024 |
| ON the Crest of the Wave Consulting Ltd | Professional & scientific | 2025 |
| ON the Day . Co . UK Ltd | Administrative & support | 2025 |
| ON the Go Vehicle Services Ltd | Wholesale & retail | 2023 |
| ON the MAP Entertainment Ltd | Information & communication | 2026 |
| ON the Trail Ltd | Hospitality | 2018 |
| ON Top Roofing Solutions Ltd | Construction | 2024 |
| On's Heritage Limited | Real estate | 2025 |
| On-Site Plant Logistics Ltd | Manufacturing | 2011 |
| Onange Limited | Real estate | 2022 |
| Onboard Entertainment Limited | Arts & recreation | 2024 |
| Onburg Ltd | Hospitality | 2021 |
| Once Upon a Time Activation Limited | Manufacturing | 1999 |
| Oncoplastic Breast Surgery Limited | Health & social care | 2017 |
| Ondot Services Ltd | Other services | 2017 |
| One 1 Stop Mini Market Ltd | Wholesale & retail | 2025 |
| One 2 One Car Audio Limited | Wholesale & retail | 2006 |
| One 2 One Support Services Nottingham Ltd | Professional & scientific | 2020 |
| One 376 Limited | Professional & scientific | 2013 |
| One Call Maintenance Limited | Administrative & support | 2020 |
| One Day Care Centre Ltd | Health & social care | 2019 |
| One DK Limited | Information & communication | 2025 |
| One Edition (UK) Ltd | Wholesale & retail | 2019 |
| One IT Consultancy Limited | Information & communication | 2019 |
| One Lettting Ltd | Hospitality | 2026 |
| One Life Holidays Limited | Administrative & support | 2019 |
| One Little Room Limited | Hospitality | 2022 |
| One More Drop Ltd | Hospitality | 2026 |
| One More Wave Ltd | Real estate | 2022 |
| One Occupational Medicine Limited | Health & social care | 2017 |
| One Percent Holdings Company Limited | Financial services | 2020 |
| One Point Four Degrees Limited | Other services | 2023 |
| One Point Four Degrees U.S. Ltd | Professional & scientific | 2025 |
| One Pound Coffee Ltd | Professional & scientific | 2024 |
| One Seal Coatings Limited | Administrative & support | 2023 |
| One Sky Travel Ltd | Arts & recreation | 2023 |
| One Stop Care (Nottingham) Limited | Health & social care | 2008 |
| One Stop Day Care Limited | Health & social care | 2024 |
| One Stop Drinks Limited | Wholesale & retail | 2021 |
| One Stop Glazing Consultants Ltd | Professional & scientific | 2022 |
| One Stretch Ltd | Administrative & support | 2023 |
| One Swan Software Ltd | Information & communication | 2026 |
| One Tech Alpha Limited | Wholesale & retail | 2024 |
| One Tribe Campaign CIC | Hospitality | 2019 |
| One Vision Partnership Limited | Other services | 2001 |
| One-Nil to the Arsenal Limited | Financial services | 1999 |
| ONE5 Leisure Limited | Hospitality | 2013 |
| Oneaza Digital Services Limited | Wholesale & retail | 2025 |
| Oneboxout Ltd | Information & communication | 2020 |
| Onegrowth Ltd | Information & communication | 2025 |
| Onehaus Collective Limited | Professional & scientific | 2010 |
| Oneloft Ltd | Wholesale & retail | 2025 |
| Oneman Network Limited | Information & communication | 2025 |
| Oneness Entertainment Ltd | Information & communication | 2019 |
| Oneness Holdings Limited | Financial services | 2025 |
| Onesafety Ltd | Professional & scientific | 2004 |
| Oneskee Clothing Ltd | Wholesale & retail | 2024 |
| Onestop Interiors Limited | Wholesale & retail | 2016 |
| Oneten Domestic Limited | Transport & logistics | 2024 |
| Onetouchgraphitech Ltd | Construction | 2019 |
| Onezo Ltd | Information & communication | 2017 |
| Onicars Ltd | Wholesale & retail | 2025 |
| Onit Construction Limited | Construction | 2007 |
| Online Accounting Limited | Extraterritorial | 2016 |
| Online Avenue Limited | Wholesale & retail | 2025 |
| Online Carpet Remnants Ltd | Wholesale & retail | 2020 |
| Online Cosmetic Partners Limited | Extraterritorial | 2013 |
| Online Delivery Chemist Ltd | Health & social care | 2022 |
| Online Shop Catalogue Ltd | Administrative & support | 2017 |
| Online Van Hub Limited | Wholesale & retail | 2013 |
| Onlinerisks Limited | Information & communication | 1999 |
| Only Kams Ltd | Construction | 2026 |
| Only Notts CIC | Arts & recreation | 2025 |
| Onlyda Limited | Wholesale & retail | 2019 |
| ONO Energy Limited | Professional & scientific | 2014 |
| Onoasi Services Limited | Information & communication | 2015 |
| Onpar Official Ltd | Wholesale & retail | 2026 |
| Onpoint Distribution Ltd | Professional & scientific | 2013 |
| Onpoint IT Limited | Information & communication | 1997 |
| Onri Limited | Professional & scientific | 2018 |
| Onriva Ltd | Information & communication | 2025 |
| Onside Enterprises Limited | Wholesale & retail | 2005 |
| Onside Productions Ltd | Information & communication | 2017 |
| Onsun Limited | Construction | 2015 |
| Ontap Management Limited | Hospitality | 2025 |
| Ontime Contractors Limited | Construction | 2022 |
| Ontop Electrical Ltd | Construction | 2011 |
| Onyeabo Obasi Services Limited | Health & social care | 2007 |
| Onyx Care Solutions Ltd | Administrative & support | 2017 |
| Onyx Circulus Ltd | Professional & scientific | 2023 |
| Onyx Consortium Ltd | Financial services | 2019 |
| Onyx Consult Ltd | Professional & scientific | 2016 |
| Onyx Goldsmiths Limited | Wholesale & retail | 1997 |