| North Lodge Park (Milton) Management Company Limited | Real estate | 2013 |
| Northgate House (Exeter) Freehold Company Limited | Professional & scientific | 2015 |
| Northgate House (Exeter) Owners Limited | Households | 2013 |
| Northstowe Residents Management Company Limited | Households | 2018 |
| Norton Heath Management Limited | Construction | 2017 |
| NOT Just Bags Ltd | Administrative & support | 2025 |
| Notton Wood View (Royston) Management Company Limited | Households | 2018 |
| NPJ Industrial Ltd | Construction | 2024 |
| NRH Consultancy Ltd | Education | 2021 |
| NTK Communications Limited | Professional & scientific | 2024 |
| Number Sixty Two Warwick Road (Management) Limited | Households | 1983 |
| Nutford Place Management Limited | Households | 2010 |
| O'Brien Property Services Limited | Real estate | 1987 |
| Oak Grange Management Company Limited | Households | 2005 |
| Oak Moor View Launceston Management Company Limited | Households | 2010 |
| Oak Moor View Launceston Management Company Plots Limited | Households | 2010 |
| Oak Park (Cheddar) Management Company Limited | Households | 2022 |
| Oak Tree Court Residents Association Limited | Real estate | 1971 |
| Oak Tree Place Phase 2 (Hedge END) Management Company Limited | Households | 2009 |
| Oakbrook (Marston Green) Management Company Limited | Households | 2018 |
| Oakenhall (Stantonbury) Management Company Limited | Households | 2009 |
| Oakfield Swindon Residents Management Company Limited | Households | 2023 |
| Oakford Grange (Telford) Management Company Limited | Households | 2014 |
| Oakhill Park (Saffron Walden) Residents Management Company Limited | Households | 2010 |
| Oakland Road (Moseley) Management Company Limited | Households | 2018 |
| Oakleaf Place (Management Company) Limited | Households | 2018 |
| Oakleaf Place Management Company Limited | Households | 2002 |
| Oakleigh Park Drive RTM Company Limited | Households | 2025 |
| Oakley Grange & Eden Villas (Cheltenham) Management Company Limited | Households | 2016 |
| Oakley Park (Edenbridge) Management Company Limited | Real estate | 2018 |
| Oaks Basketball Camps Ltd | Arts & recreation | 2026 |
| Oaktree Place PH3 (Hedge END) Management Company Limited | Households | 2012 |
| Oakwell Mews (Bickington) Management Company Ltd | Households | 2018 |
| Oakwood Court (Management) Limited | Households | 1971 |
| Oakwood Eco Homes Limited | Construction | 2023 |
| Oakwood Hill (Halstead) Management Company Limited | Real estate | 2018 |
| Oasis at Lincoln Management Company Limited | Households | 2011 |
| Ocean Breeze (Barton on Sea) Limited | Real estate | 2011 |
| Ocean Heights (Porthtowan) Management Company Limited | Real estate | 2016 |
| Odeum Group Ltd | Construction | 2024 |
| Offers View (Devizes) Management Company Limited | Real estate | 2013 |
| Ohos Properties Limited | Real estate | 2024 |
| Ojsinvest Limited | Financial services | 2019 |
| Okement Park (Okehampton) Management Company Limited | Households | 2022 |
| Okemont Grove Okehampton Management Company Limited | Households | 2010 |
| Old School Drive (Wheathampstead) Management Company Limited | Households | 2010 |
| Old Vine Town House Limited | Real estate | 2025 |
| Olive Farm (Hoghton) Managing Company Limited | Professional & scientific | 2021 |
| Olive Logistics Ltd | Transport & logistics | 2024 |
| Olives Direct Limited | Wholesale & retail | 2004 |
| Olton Hollow Management Company Limited | Households | 2005 |
| Olympia (Hall Green) Management Company Limited | Households | 2019 |
| Omoc Consulting Ltd | Professional & scientific | 2024 |
| One Montagu Place Limited | Households | 1985 |
| One on Refresh Ltd | Professional & scientific | 2022 |
| Onyx Contracting Group Ltd | Construction | 2022 |
| OO Infinity Limited | Wholesale & retail | 2023 |
| Opsm Limited | Households | 2018 |
| ORA Events Limited | Professional & scientific | 2014 |
| Orchard Court (Trowbridge) Management Company Limited | Households | 1989 |
| Orchard Gate (Shoreham) Management Company Limited | Households | 2010 |
| Orchard Grove (Farnham) Management Company Limited | Households | 2002 |
| Orchard Mews Pershore Management Company Limited | Households | 2022 |
| Orchard Place (Clacton on Sea) Management Company Limited | Households | 2020 |
| Orchid House (Whitworth Road) RTM Company Limited | Households | 2026 |
| Orpington (Station Road) Management Company Limited | Professional & scientific | 2006 |
| Orwell Park (Sutton Courtenay) Management Company Limited | Real estate | 2021 |
| Oscen Limited | Wholesale & retail | 2013 |
| Oslar Coffee Ltd | Hospitality | 2012 |
| Otter Way Cranbrook Management Company Limited | Households | 2013 |
| Outboard Motors Ltd | Manufacturing | 2024 |
| Outdoor Learning Academy Ltd | Other services | 2024 |
| Outright Adventure (New Forest) CIC | Education | 2024 |
| Outright Adventure Community Interest Company | Education | 2015 |
| Outright Hosting Limited | Information & communication | 2022 |
| Overcliff Court (Management) Limited | Households | 1983 |
| Overton Residents Association Limited | Households | 2007 |
| Oxford Heights (Southampton) Management Company Limited | Households | 2016 |
| Oxley Gardens at Milton Keynes Management Company Limited | Professional & scientific | 2016 |
| Oxley Park (A18) Management Company Limited | Households | 2007 |
| Oxley Springs (Milton Keynes) Management Company Limited | Households | 2011 |
| Oxley Springs 8B (Milton Keynes) Management Company Limited | Households | 2012 |
| P & a Shopfitting Limited | Construction | 2014 |
| P Dalton and Sons Limited | Construction | 2019 |
| P Gazzard Construction Limited | Construction | 2015 |
| P J Greenacre & Co Limited | Professional & scientific | 1996 |
| P Mcmahon Builders Limited | Professional & scientific | 2018 |
| P&C Premier Barbeque and Catering Ltd | Hospitality | 2019 |
| P&C Premier Events Ltd | Construction | 2021 |
| Padbury Fold (Padbury) Residents Management Company Limited | Households | 2019 |
| Paddock Fields (Killinghall) Management Company Limited | Households | 2018 |
| Paddock Fields II (Killinghall) Management Company Limited | Households | 2018 |
| Pages Priory Phase Two (Leighton Buzzard) Management Company Limited | Households | 2007 |
| Palm Cross Management Company Limited | Administrative & support | 2016 |
| Palm Cross Phase 2 Management Company Limited | Households | 2019 |
| Paquetego Ltd | Transport & logistics | 2025 |
| Park Gate (Hurcott) Management Company Limited | Real estate | 2020 |
| Parkgate Mews Residents Management Company Limited | Households | 2014 |
| Parklands (Shoeburyness) Management Company Limited | Households | 2008 |
| Parklands (Woburn Two) Management Company Limited | Households | 2008 |