| OJW Services (M&E) Ltd | Construction | 2022 |
| Old 2 New Developments Ltd | Construction | 2025 |
| Old Church Road (Terrington) Management Ltd | Households | 2020 |
| Old England Ltd | Hospitality | 2011 |
| Old Forge Yard Residents Limited | Households | 2018 |
| Old Hall Country Breaks Limited | Hospitality | 2019 |
| Old Hall Farm Holidays (East) Limited | Real estate | 2025 |
| Old Sunway Management Company Limited | Real estate | 2023 |
| Olde England Ales Ltd | Manufacturing | 2016 |
| Olde England Limited | Hospitality | 2011 |
| Olegon Limited | Transport & logistics | 2024 |
| Olive Construction (Norfolk) Ltd | Construction | 2022 |
| Olive MAY Analytics Limited | Professional & scientific | 2017 |
| Ollie Robinson Property Limited | Construction | 2025 |
| Ollies Restaurant Ltd | Hospitality | 2013 |
| Ollies Street Food Ltd | Hospitality | 2025 |
| Omex Vitech Limited | Manufacturing | 2013 |
| OMG Shimmer Ltd | Administrative & support | 2024 |
| Ommoti Limited | Real estate | 2017 |
| Omnivista Ltd | Public administration | 2025 |
| Omsai Locums Limited | Real estate | 2016 |
| ON Site Assessment and Training Services (UK) Limited | Education | 2013 |
| Oncologica UK Limited | Health & social care | 2014 |
| One Catering Ltd | Hospitality | 2025 |
| One in Haul Limited | Transport & logistics | 2026 |
| One Million Hours Limited | Professional & scientific | 2024 |
| One N SIX Care Ltd | Health & social care | 2026 |
| One Nine Solutions Limited | Professional & scientific | 2018 |
| One Stop Science & Nature Ltd | Wholesale & retail | 2011 |
| One Training Solutions Ltd | Education | 2020 |
| Onetwentyone Consulting Ltd | Information & communication | 2026 |
| Only Estates Limited | Wholesale & retail | 2007 |
| Onlyyellowcars Ltd | Wholesale & retail | 2022 |
| Onorigin Limited | Information & communication | 2016 |
| Opek Ltd | Professional & scientific | 2022 |
| Open Estate Investments Limited | Real estate | 2020 |
| Open Globe Limited | Hospitality | 1998 |
| Open Hands Home Buyers Limited | Other services | 2020 |
| Openmart Limited | Hospitality | 1994 |
| Opium Hair Design Limited | Other services | 2009 |
| Optilink Solutions Ltd | Information & communication | 2026 |
| Optima Metal Services Ltd | Extraterritorial | 2018 |
| Optima Stainless Limited | Manufacturing | 2009 |
| Optimum Developments (Norfolk) Ltd | Construction | 2019 |
| Optimum Stoves Ltd | Construction | 2026 |
| Optimyzd Ltd | Professional & scientific | 2019 |
| Optiscript Solutions Ltd | Manufacturing | 2025 |
| Orbitglobal Ltd | Wholesale & retail | 2026 |
| Orca Homes Ltd | Real estate | 2025 |
| Orchard Close (Tilney) Management Company Ltd | Households | 2019 |
| Orchard Farm Estates ( Counties ) Prop Co. Ltd | Real estate | 2019 |
| Orchard Farm Estates (Counties) Ltd | Administrative & support | 2017 |
| Orchard Healthcare (Norfolk) Ltd | Health & social care | 2022 |
| Orchard House Consultants Limited | Professional & scientific | 2013 |
| Orchard R&K Ltd | Real estate | 2025 |
| Ordu Takeaway Ltd | Hospitality | 2025 |
| Orlando Investments Limited | Real estate | 2018 |
| Osborne Wolf Limited | Professional & scientific | 2016 |
| Osiaris Ltd | Real estate | 2015 |
| Osvaldas & Laima Limited | Transport & logistics | 2018 |
| OTE Catering Ltd | Hospitality | 2020 |
| Outerside Ltd | Arts & recreation | 2025 |
| Outrageous (KL) Ltd | Wholesale & retail | 2024 |
| Overland Autos Ltd | Manufacturing | 2026 |
| Owen and Davenport Installation and Construction Limited | Construction | 2002 |
| Owens D.I.Y. Limited | Wholesale & retail | 2006 |
| Owloc Industries Ltd | Manufacturing | 2012 |
| Oxborough Farms Limited | Agriculture & fishing | 1963 |
| Oxicoco Ltd | Wholesale & retail | 2008 |
| Oxwillow Farming Company Ltd | Agriculture & fishing | 2025 |
| Oxwillow Ltd | Professional & scientific | 2023 |
| P C Construction Services Ltd | Construction | 2016 |
| P J & B Jones Ltd | Administrative & support | 2003 |
| P Smith Building and Maintenance Ltd | Construction | 2026 |
| P&H Removals Ltd | Transport & logistics | 2016 |
| P.D. Avionics Limited | Professional & scientific | 2012 |
| P.D. Moden Ltd. | Construction | 2008 |
| P.K.S. Group (DM) Limited | Financial services | 2025 |
| P3C Holdings Limited | Financial services | 2025 |
| Padel Dynamic Limited | Construction | 2025 |
| Paegon Limited | Professional & scientific | 2025 |
| Pagen Dynamics Limited | Construction | 2015 |
| PAH Law Limited | Professional & scientific | 2018 |
| Paint Genie Repairs Limited | Manufacturing | 2011 |
| Paladin Imports Limited | Construction | 1994 |
| Pandith Properties Ltd | Real estate | 2023 |
| Pangea Developments Limited | Real estate | 2019 |
| Panks Driver Supply Ltd. | Transport & logistics | 2015 |
| Paris’ Childcare Services Ltd | Health & social care | 2026 |
| Park Farm Tea Rooms Limited | Hospitality | 2023 |
| Parker-Colman Limited | Professional & scientific | 2020 |
| Parlour Press Ltd | Other services | 2003 |
| Parmell Consultancy Services Limited | Extraterritorial | 2012 |
| Pastures View Management Company Limited | Households | 2017 |
| Patché Corporation Ltd | Manufacturing | 2025 |
| Paul Carr Advertising Limited | Professional & scientific | 2009 |
| Paul Cross Travel Ltd | Transport & logistics | 2010 |
| Paul Johnson Motor Services Ltd. | Wholesale & retail | 1999 |
| Paul Massingham Plastering & Rendering Ltd | Construction | 2014 |
| Paul Thraxton Consultancy Services Limited | Information & communication | 2017 |