| Ouro Boros Labs Limited | Information & communication | 2024 |
| Ouro Rosa Ltd | Administrative & support | 2024 |
| Outdoor Formats Limited | Professional & scientific | 2012 |
| Outfit International UK Limited | Wholesale & retail | 2019 |
| Outfit Outlet Ltd | Wholesale & retail | 2025 |
| Outgrw Ltd | Information & communication | 2023 |
| Outside Productions Ltd | Information & communication | 2025 |
| Outwood Lane Residents Association Limited | Households | 2011 |
| OV Building Services Limited | Construction | 2014 |
| Oval House Freehold Limited | Real estate | 2019 |
| Ovalbeech Limited | Health & social care | 1985 |
| Ovalcrest Limited | Construction | 2018 |
| Ovalcrest Management Limited | Real estate | 2025 |
| Oven Sheen Ltd | Other services | 2006 |
| Over the Channel Limited | Hospitality | 2013 |
| Over the Top Thobes Limited | Wholesale & retail | 2025 |
| Overflow Consulting Ltd | Professional & scientific | 2025 |
| Overthrow Recordings Limited | Arts & recreation | 2014 |
| Overton Toft Management Limited | Households | 1989 |
| Ovester Limited | Information & communication | 2007 |
| OVW Investments Limited | Financial services | 2022 |
| Owen Properties Limited | Construction | 1981 |
| Owens General Store Limited | Wholesale & retail | 2012 |
| Owiu PTS Limited | Construction | 2019 |
| OWL Alarm Systems Limited | Construction | 1986 |
| OWL FIX IT Ltd | Construction | 2022 |
| OWL FIX IT Plumbing & Heating Services Ltd | Construction | 2020 |
| Ownit Property Services Limited | Transport & logistics | 2025 |
| Oxagon IT Services Ltd | Information & communication | 2007 |
| Oxagon Web IT Services Ltd | Information & communication | 2008 |
| Oxalis Games Ltd | Information & communication | 2020 |
| Oxenham Court (Management) Company Limited | Households | 2005 |
| Oxford Court Management Company (Carnforth) Limited | Real estate | 2008 |
| Oxford Court Residents (Leigh) Limited | Households | 2006 |
| Oxgram Limited | Real estate | 2024 |
| Oxton Court Limited | Households | 2020 |
| Oxton Lawns Management Company Limited | Households | 2003 |
| Oyin Healthcare Provider Limited | Health & social care | 2021 |
| Oyster BED Ltd | Professional & scientific | 2013 |
| Oyster Care Services Limited | Health & social care | 2021 |
| Oyyr Capital Ltd | Construction | 2025 |
| OZ Nation Ltd | Professional & scientific | 2024 |
| Ozcan Charcoal Grill Limited | Hospitality | 2025 |
| Ozdem Catering Limited | Hospitality | 2006 |
| Ozdemir Mobile Chef Ltd | Hospitality | 2021 |
| Ozdev Ltd | Real estate | 2017 |
| Ozen Foods Limited | Hospitality | 2023 |
| Ozen London Ltd | Hospitality | 2023 |
| Ozer Taha Property Ltd | Real estate | 2025 |
| Ozgur Trans & Projects Ltd | Transport & logistics | 2024 |
| Oznaz Ltd | Professional & scientific | 2019 |
| Ozner Medikal Sanayi VE Ticaret (London) Ltd | Manufacturing | 2022 |
| Ozozir Ltd | Hospitality | 2025 |
| OZR Ltd | Professional & scientific | 2018 |
| Ozumba Training and Consultancy Services Limited | Professional & scientific | 2015 |
| Ozzie's Barber Company 1 Limited | Other services | 2018 |
| O’Neill Property Developments Ltd | Real estate | 2023 |
| P & C Ice Cream Ltd | Administrative & support | 2012 |
| P & E Rentals Limited | Real estate | 2019 |
| P & F Andrade Limited | Hospitality | 2002 |
| P & G (GB) Ltd | Wholesale & retail | 2012 |
| P & I Dyer Limited | Transport & logistics | 2008 |
| P & J Logistical Limited | Transport & logistics | 2018 |
| P & R Mini Market Limited | Wholesale & retail | 2002 |
| P & T Transport Courier and Logistics Limited | Transport & logistics | 2016 |
| P & W Contractor Limited | Construction | 2025 |
| P and M House Clearances Limited | Administrative & support | 2012 |
| P Chatelier Electrical Limited | Construction | 2014 |
| P D Ackland Ltd | Professional & scientific | 2013 |
| P Driver Media Ltd | Information & communication | 2025 |
| P K B Homes Limited | Real estate | 2019 |
| P L Convenience Limited | Wholesale & retail | 2011 |
| P S Anderman Limited | Professional & scientific | 2003 |
| P&D Interiors Limited | Construction | 2020 |
| P&E Properties Management (UK) Ltd | Real estate | 2022 |
| P&J Building Contractors Ltd | Construction | 2015 |
| P&K Pro Cleaning Services Ltd | Administrative & support | 2024 |
| P&R Promotions Ltd | Administrative & support | 2017 |
| P'S Tax Haven Consultancy Ltd | Professional & scientific | 2025 |
| P.A.D Academy CIC | Information & communication | 2025 |
| P.B. Baumann (UK) Limited | Wholesale & retail | 1994 |
| P.D.L. Limited | Administrative & support | 1999 |
| P.E. Bleu Ltd | Real estate | 2024 |
| P.F. Whitehead Storage Limited | Professional & scientific | 1977 |
| P.F.W. Properties Limited | Transport & logistics | 1983 |
| P.Frost Services Ltd | Construction | 2020 |
| P.J. Roofing Limited | Wholesale & retail | 1997 |
| P.Kingham Limited | Wholesale & retail | 1960 |
| P.P. Building Contractors Limited | Construction | 1988 |
| P4YE Ltd | Education | 2021 |
| P5 Projects Limited | Professional & scientific | 2016 |
| P6 Developments Limited | Professional & scientific | 2023 |
| P6 Investments Ltd | Real estate | 2025 |
| PAB Advisory Ltd | Administrative & support | 2016 |
| Pabegti Ltd | Construction | 2016 |
| PAC Commercial Interiors Limited | Construction | 2014 |
| Pacestar Building Services Ltd | Construction | 1998 |
| Pacestar Holdings Limited | Manufacturing | 2025 |
| Pacestar Joinery UK Ltd | Manufacturing | 2005 |
| Pacestar Trading Ltd | Wholesale & retail | 2019 |