| Olafflee Ltd | Professional & scientific | 2023 |
| Old Crow Models Ltd | Arts & recreation | 2023 |
| Olectrics Ltd | Administrative & support | 2018 |
| Olly Martin Lighting Ltd | Information & communication | 2023 |
| Olward Ltd | Transport & logistics | 2018 |
| Olympus Flooring Limited | Construction | 1999 |
| Omega Home Refurbishment Ltd | Construction | 2019 |
| Omni Enterprise Ltd | Wholesale & retail | 2018 |
| Omni X Solution Ltd | Wholesale & retail | 2025 |
| Omnivae Ltd | Wholesale & retail | 2026 |
| Omshiv Investments Limited | Real estate | 2023 |
| ON Sixteenth Limited | Wholesale & retail | 2019 |
| Oncolytics Medical Ltd | Health & social care | 2021 |
| One Cause Limited | Administrative & support | 2007 |
| One Haulage Ltd | Transport & logistics | 2020 |
| One More Kando LLP | | 2026 |
| One More TCG Limited | Wholesale & retail | 2025 |
| One Shot Utilities Ltd | Construction | 2024 |
| Onestandard Limited | Professional & scientific | 2025 |
| Onfries Ltd | Hospitality | 2022 |
| Onome Healthcare Ltd | Health & social care | 2022 |
| Onsite Developments Design & Construction Ltd | Construction | 2007 |
| Onsite Developments Limited | Construction | 2017 |
| Onslow Gardens Property Management Ltd | Households | 2013 |
| Onyx Developments Limited | Real estate | 2005 |
| Onyx Management Limited | Information & communication | 1998 |
| Opacza Ltd | Arts & recreation | 2024 |
| Open Brief Limited | Administrative & support | 2002 |
| Opendesk Ltd | Information & communication | 2026 |
| Oportfolio Properties Ltd | Real estate | 2020 |
| Oportfolio Wealth & Estates Ltd | Other services | 2024 |
| Optiedu Ltd | Administrative & support | 2025 |
| Opulent 8 Properties Limited | Real estate | 2024 |
| Opulent Pools Limited | Construction | 2016 |
| Opulent Pools Surrey Ltd | Construction | 2026 |
| Orbis Electrics Limited | Construction | 2014 |
| Orbitex Trading Ltd | Wholesale & retail | 2018 |
| Orchid Nails Wallington Ltd | Other services | 2022 |
| Orcrest Residents Company Limited | Households | 1973 |
| Organic Estates Ltd | Real estate | 2022 |
| Oria Commerce Limited | Professional & scientific | 2003 |
| Oriel Court (Sutton) Management Limited | Households | 1995 |
| Orion Blue Limited | Information & communication | 2015 |
| Ortega Consultancy Ltd | Administrative & support | 2016 |
| OSA Grace Ltd | Professional & scientific | 2023 |
| OSA Grace Properties Ltd | Real estate | 2023 |
| Oscps Motion Sensing Ltd | Manufacturing | 2024 |
| Ottraco Limited | Health & social care | 2003 |
| Ouipui Ltd | Professional & scientific | 2012 |
| Outdoor Living (London) Limited | Administrative & support | 2019 |
| Outris Imaging Limited | Information & communication | 2025 |
| Outsider Productions Ltd | Arts & recreation | 2020 |
| OVE Ltd | Health & social care | 2023 |
| OVI Buildings Services Ltd | Construction | 2018 |
| Ovid Consulting Ltd | Professional & scientific | 2018 |
| Owna Childcare Apps Ltd | Information & communication | 2019 |
| Oxford Adams Limited | Administrative & support | 2013 |
| Oxford Energie Ltd | Professional & scientific | 2022 |
| Oyyo Co., Ltd | Wholesale & retail | 2024 |
| OZ Groom Barbers Ltd | Other services | 2024 |
| OZ Grooming Wallington Limited | Other services | 2019 |
| OZ Pet Services Limited | Agriculture & fishing | 2024 |
| P D Building Services Limited | Construction | 2016 |
| P Hickey (Labour Supply) Limited | Construction | 1997 |
| P Hickey (Plant Hire) Limited | Administrative & support | 1990 |
| P Hickey Group Limited | Construction | 1989 |
| P M Hitchin Contracts Limited | Construction | 2008 |
| P R Medical Ltd | Health & social care | 2022 |
| P S White Ltd | Transport & logistics | 2024 |
| P Sqaure Technologies Limited | Information & communication | 2014 |
| P&A Partners Ltd | Administrative & support | 2020 |
| P. Styllis Limited | Other services | 1980 |
| P.P.M.A. Limited | Other services | 1987 |
| P.Smith Engineers Limited | Professional & scientific | 2013 |
| P4YWATCH Limited | Professional & scientific | 2024 |
| PA Group Retail Limited | Wholesale & retail | 2019 |
| PAA Interiors Limited | Construction | 2012 |
| Padawan Outpost Ltd | Wholesale & retail | 2020 |
| Paddle Ducks LLP | | 2023 |
| Padgett Consulting Ltd | Professional & scientific | 2024 |
| Paediatric Healthcare Ltd | Health & social care | 2024 |
| PAK Technology Limited | Health & social care | 2014 |
| Palace and Castle Ltd | Real estate | 2020 |
| Palniq Limited | Information & communication | 2026 |
| Panache Pupz Ltd | Wholesale & retail | 2017 |
| Panaf Mining Ltd | Mining & quarrying | 2022 |
| Paojus Health Care Limited | Health & social care | 2025 |
| Papris IT UK Ltd | Information & communication | 2015 |
| Paradise Pointe Ltd | Hospitality | 2024 |
| Paragon Driving School Limited | Education | 2022 |
| Paragon Nomad Ltd | Wholesale & retail | 2026 |
| Parch Hill Wallington Ltd | Education | 2019 |
| Parcha Production Limited | Arts & recreation | 2015 |
| Parent Hub UK Ltd | Information & communication | 2023 |
| Parker Meller Limited | Real estate | 2007 |
| Parkinson Business Limited | Administrative & support | 2020 |
| Parkwood House Property Management Ltd | Households | 2022 |
| Parrot Quay Limited | Financial services | 2020 |
| Party Pronto Limited | Arts & recreation | 2013 |
| Pascal Adr&Vas Ltd | Transport & logistics | 2023 |