| Noxterra Academy Limited | Education | 2021 |
| Noxterra Limited | Agriculture & fishing | 2021 |
| NSB Global Ltd | Hospitality | 2026 |
| Nu-Facades Limited | Construction | 2018 |
| Nude Yoga Girl Limited | Administrative & support | 2015 |
| Nugsau Limited | Arts & recreation | 2022 |
| Nurtur'D Ltd | Manufacturing | 2019 |
| Nynes Designs Ltd | Arts & recreation | 2024 |
| O & P Financial Services Limited | Administrative & support | 2014 |
| O'Brien Engineering Consultancy Ltd | Professional & scientific | 2012 |
| O.Allison Ltd | Manufacturing | 2025 |
| Oakdene Windows Ltd | Manufacturing | 2025 |
| Oakenshore Limited | Administrative & support | 2015 |
| Oakley Building Ltd | Construction | 2021 |
| Oakwood Classic Cars Ltd | Wholesale & retail | 2019 |
| Oakwood Pest Control Ltd | Administrative & support | 2024 |
| Oatcakes Pet Lodge Limited | Other services | 2016 |
| OB Vending Ltd | Wholesale & retail | 2025 |
| Obsidian Systems Ltd | Information & communication | 2025 |
| OC Construction & Carpentry Ltd | Construction | 2017 |
| OC Motorsport Ltd | Wholesale & retail | 2017 |
| Ocean Car Valeting Centre Ltd | Administrative & support | 2023 |
| Oceanis Group Ltd | Construction | 2006 |
| OCL Group Limited | Real estate | 2015 |
| OCL Recruitment Limited | Extraterritorial | 2015 |
| OCL Site Management Limited | Construction | 2016 |
| Octave House Flat Owners Limited | Real estate | 2014 |
| Octupus AI Ltd | Information & communication | 2024 |
| ODP Armstrong Limited | Health & social care | 2015 |
| ODU Intellect CIC | Information & communication | 2026 |
| Office Manager UK Limited | Administrative & support | 2017 |
| Offshore Contracts Limited | Construction | 2025 |
| Offsite Cloud Ltd. | Information & communication | 2009 |
| OG Carpentry & Building Services Ltd | Manufacturing | 2021 |
| OHR Strategic Consulting Ltd | Professional & scientific | 2024 |
| Okelly Property Investments Limited | Real estate | 2021 |
| Olayinka's Kitchen Limited | Manufacturing | 2025 |
| Olive Building Ltd | Construction | 2016 |
| Oliver Greene Ltd | Real estate | 2020 |
| Olives & Dates CIC | Wholesale & retail | 2021 |
| OLS Electrical Services Ltd | Construction | 2026 |
| Omen Design Studio Ltd | Professional & scientific | 2021 |
| OML (Partners) Ltd | Professional & scientific | 2013 |
| Omnia Creations Ltd | Financial services | 2018 |
| Omnium Racing Limited | Arts & recreation | 2017 |
| One Stop Locksmiths Limited | Other services | 2008 |
| One to Many Solutions Limited | Information & communication | 2017 |
| Online Office Supplies Ltd | Wholesale & retail | 2025 |
| Online Techniques Ltd | Information & communication | 2011 |
| Only Tanss Ltd | Other services | 2024 |
| Only Vans Essex Ltd | Wholesale & retail | 2023 |
| Onlyforklift Ltd | Administrative & support | 2026 |
| Onslow C RTM Company Limited | Households | 2024 |
| Onwards and Upwards UK Inc Ltd | Professional & scientific | 2012 |
| Oosh Media Ltd | Information & communication | 2023 |
| Opal QA Ltd | Administrative & support | 2012 |
| Opal South East England Limited | Education | 2024 |
| Opryx Limited | Administrative & support | 2025 |
| Optimise Electrical Ltd | Construction | 2021 |
| Optimise Group Ltd | Construction | 2016 |
| Optimise Mechanical Ltd | Construction | 2021 |
| Optimum RBM Limited | Construction | 2019 |
| ORA Home Limited | Wholesale & retail | 2000 |
| Oracle Plant Hire Limited | Other services | 2018 |
| Orange Tree Financial Services Limited | Professional & scientific | 2017 |
| Orbital Hygiene Services Limited | Wholesale & retail | 1985 |
| Organically Epic Limited | Wholesale & retail | 2021 |
| Oriana & Pedro Limited | Hospitality | 2017 |
| Origin Clothing Worldwide Ltd | Wholesale & retail | 2023 |
| Orol Ltd | Transport & logistics | 2015 |
| Osborne Properties Ltd | Real estate | 2021 |
| Osku Catering Limited | Hospitality | 2017 |
| Otiscare Ltd | Professional & scientific | 2022 |
| OUT of the Ashes Ltd | Professional & scientific | 2022 |
| Overton Vehicle Overhauls Limited | Wholesale & retail | 2000 |
| Overtons Costs Consultants Limited | Other services | 2014 |
| Owili Limited | Health & social care | 2021 |
| OX Live Ltd | Administrative & support | 2019 |
| OXY Limited | Information & communication | 2022 |
| Ozkisi Catering Limited | Hospitality | 2019 |
| P & D Paving Limited | Construction | 2005 |
| P & G Property Limited | Real estate | 2011 |
| P & L Moving Solutions Limited | Transport & logistics | 2023 |
| P Bunn Brickwork Limited | Construction | 2015 |
| P I P Engineering Ltd | Professional & scientific | 2019 |
| P M C Distribution Limited | Wholesale & retail | 2025 |
| P&M Padel Courts Ltd | Arts & recreation | 2026 |
| P. & S. Bird Limited | Transport & logistics | 2017 |
| P.A. Risk Commercial Tyre Services Limited | Wholesale & retail | 2002 |
| Pacific Pools Limited | Wholesale & retail | 1991 |
| PAD Accountancy Services Limited | Professional & scientific | 2006 |
| Page Brothers Rendering Ltd | Construction | 2020 |
| PAN OUT Limited | Information & communication | 2018 |
| Panel Pixels Ltd | Information & communication | 2025 |
| Paramount Multi Services Ltd | Construction | 2015 |
| Parasees Marketing Limited | Health & social care | 2025 |
| PARDZ23 Limited | Wholesale & retail | 2025 |
| Parents 1ST Limited | Extraterritorial | 2008 |
| Park Drive Health Club Ltd | Arts & recreation | 2021 |
| Park Home Refurbishments Limited | Construction | 2009 |