| Old Barrack Fish and Chips Ltd | Hospitality | 2024 |
| Old Cannon Holdings Limited | Real estate | 2006 |
| Old Hall Farm Flat Management Co. Limited | Households | 2006 |
| Old JET Limited | Arts & recreation | 2014 |
| Old Oak Cattery Limited | Hospitality | 2013 |
| Old Rectory Court Maintenance Company Limited | Households | 1990 |
| Oliver Bower Limited | Professional & scientific | 2022 |
| Oliver Farm Recycling Ltd | Water & waste | 1972 |
| Oliver Leeder Accountants Ltd | Professional & scientific | 2015 |
| Oliver Shilling Ltd | Professional & scientific | 2018 |
| Omar Aziz Ltd | Agriculture & fishing | 2018 |
| Omnitec Ltd | Administrative & support | 2010 |
| ON the Floor Limited | Information & communication | 2012 |
| ONESTONE42 Ltd | Real estate | 2026 |
| Onwards Agency Ltd | Information & communication | 2013 |
| Onwd Holdings Ltd | Financial services | 2021 |
| Onwd Investments Ltd | Arts & recreation | 2021 |
| Onyx Collective Ltd | Wholesale & retail | 2025 |
| Opus Construction Limited | Construction | 2018 |
| Orange Block Ltd | Transport & logistics | 2017 |
| Orbi Technologies Ltd | Information & communication | 2023 |
| Orcas Properties Limited | Real estate | 2021 |
| Orchard Ventures Limited | Real estate | 1992 |
| Orford General Stores Ltd | Wholesale & retail | 2016 |
| Orford Limited | Manufacturing | 2015 |
| Orford Little House Ltd | Hospitality | 2023 |
| Organic Financial Solutions Ltd | Financial services | 2007 |
| Origin Customs Limited | Wholesale & retail | 2025 |
| Orsom Limited | Construction | 2006 |
| Orwell Offshore Management Ltd | Real estate | 2008 |
| Orwell Precision Services Limited | Manufacturing | 2000 |
| Orwell Property Management Limited | Professional & scientific | 2004 |
| Ostara Wellbeing Limited | Other services | 2022 |
| Otosan Ltd | Professional & scientific | 2023 |
| Ottie and the BEA Limited | Wholesale & retail | 2015 |
| Otus & Company Advisory Limited | Professional & scientific | 2002 |
| Otus Corporate Finance LLP | | 2004 |
| OUR Rainbows END Ltd | Wholesale & retail | 2025 |
| Outsourced Finance Director Limited | Professional & scientific | 2023 |
| Over the Moon 73 Limited | Hospitality | 2025 |
| Owenduff Ltd | Administrative & support | 2016 |
| Owls Green Electrical Ltd | Construction | 2026 |
| Owls Retreat Limited | Other services | 2020 |
| Oxbow Electrical Ltd | Construction | 2023 |
| Oxlade & Bond Limited | Professional & scientific | 2004 |
| Oyster Search & Selection Limited | Administrative & support | 2008 |
| P F Travel Limited | Transport & logistics | 2018 |
| P&P Investors Ltd | Hospitality | 2023 |
| P. Tuckwell Limited | Wholesale & retail | 1974 |
| P.C.C. Int'L Ltd | Financial services | 2011 |
| P1 - the People First Company Ltd | Administrative & support | 2025 |
| Page Shepherd Associates Ltd | Information & communication | 2010 |
| PAL Property Holdings Ltd | Real estate | 2017 |
| Palazzo Publishing Limited | Information & communication | 2015 |
| Pamela Ormerod Farming Limited | Agriculture & fishing | 2024 |
| Paperhouse Properties Ltd | Administrative & support | 2019 |
| Paragon Landscapes and Tree Services Ltd | Administrative & support | 2018 |
| Parham Pigs Limited | Agriculture & fishing | 2017 |
| Park Farm Vineyard Ltd | Agriculture & fishing | 2024 |
| Park Properties (Anglia) Limited | Construction | 1987 |
| Park Properties Holdings Ltd | Real estate | 2023 |
| Park Properties New Homes Ltd | Real estate | 2016 |
| Park Sims Associates Limited | Professional & scientific | 2004 |
| Parkberry Ltd | Real estate | 2012 |
| Parkinson Consultants Limited | Construction | 2026 |
| Parma Industries Ltd | Transport & logistics | 2019 |
| Parnell Joinery Ltd | Construction | 2025 |
| Party Shoes Ltd | Wholesale & retail | 2011 |
| Paterberg Consulting Ltd | Professional & scientific | 2025 |
| Paul Brewer Driving Services Limited | Transport & logistics | 2012 |
| Paul Bryanton Limited | Financial services | 2013 |
| Paws for New Beginnings CIC | Other services | 2023 |
| Paws for Thought Therapy (Suffolk) Limited | Education | 2022 |
| Pawticulars Pet Services Limited | Wholesale & retail | 2014 |
| Pazery Bouffard and Company Limited | Wholesale & retail | 1928 |
| Pbtf Ltd | Information & communication | 2024 |
| PCC Invoice Finance Limited | Real estate | 2022 |
| Pcci Bridging Limited | Administrative & support | 2020 |
| Pcci Factoring Limited | Financial services | 2023 |
| Peach Pictures Ltd | Professional & scientific | 2023 |
| Pebble Rocks Marketing Ltd | Professional & scientific | 2022 |
| Penalty Kick Films Limited | Administrative & support | 2013 |
| Penalty Services Limited | Administrative & support | 2017 |
| Peninsula Forestry Limited | Administrative & support | 2018 |
| Pennine Vision Consulting Ltd | Information & communication | 2011 |
| Penny Lane Computer Services Ltd | Information & communication | 2018 |
| Pensa IT Ltd | Information & communication | 2019 |
| Perform Fitness Group Ltd | Arts & recreation | 2025 |
| Perry and Croft LLP | | 2023 |
| Perry Investment Holdings Limited | Real estate | 2020 |
| Peter Wells Architects Limited | Professional & scientific | 2012 |
| Peter's Fund (Suffolk) | Real estate | 1999 |
| Peticular Limited | Administrative & support | 2011 |
| Pets in Partnership Ltd | Other services | 2009 |
| PEV Clean Ltd | Manufacturing | 2025 |
| Pevex Group Limited | Financial services | 2021 |
| Pevex Holdings Limited | Professional & scientific | 2013 |
| Pevex Trustee Limited | Financial services | 2023 |
| Phdp Global Limited | Construction | 2018 |
| Philip Webster Construction Limited | Construction | 2014 |