| Residents First C.I.C. | Households | 2024 |
| Residual Self Image Ltd | Arts & recreation | 2026 |
| Restaurants Oxford Limited | Hospitality | 2024 |
| Retentionminds Ltd | Professional & scientific | 2025 |
| Revamp OX Motors Ltd | Wholesale & retail | 2025 |
| Reviss Services (UK) Limited | Wholesale & retail | 1995 |
| REX Dingle Properties Ltd | Real estate | 2025 |
| Reynolds Way Flat Management Company Limited | Administrative & support | 1989 |
| RG DG Gifts Limited | Wholesale & retail | 2020 |
| RGA Partners Limited | Professional & scientific | 2026 |
| RHD Logistics Ltd | Transport & logistics | 2021 |
| Rhian White Ltd | Arts & recreation | 2007 |
| Rhys Lewis Consulting Limited | Professional & scientific | 2007 |
| RIC Advisors Ltd | Professional & scientific | 2013 |
| Richard Mclernon Racing Limited | Arts & recreation | 2011 |
| Richard Williams Orthodontics Ltd | Health & social care | 2025 |
| Richardarose Associates Limited | Professional & scientific | 2017 |
| Richards Associate Services Limited | Health & social care | 2024 |
| Rickman Consulting Limited | Professional & scientific | 2016 |
| Ridgeway International Defence Logistics Limited | Transport & logistics | 2022 |
| Ridgeway View Management Company Limited | Real estate | 2013 |
| Ridham 2 Limited | Construction | 1998 |
| Ridley Heron Limited | Information & communication | 1998 |
| Rightbase Ltd | Financial services | 2025 |
| Ringstead Healthcare Ltd | Administrative & support | 2021 |
| Ripple Kids Ltd | Education | 2015 |
| Riverpeace Ltd | Health & social care | 2024 |
| Rize London Limited | Wholesale & retail | 2021 |
| RM Education Assessment Ltd | Information & communication | 2024 |
| RM Education Holdings Ltd | Financial services | 2024 |
| RM Education Ltd | Information & communication | 1973 |
| RM Educational Resources Ltd | Wholesale & retail | 1995 |
| RM PLC | Professional & scientific | 1983 |
| RMG Fencing Ltd | Construction | 2022 |
| Ro's Property Ltd | Real estate | 2024 |
| Road Productions Ltd | Arts & recreation | 2012 |
| Roadside Asset Management Limited | Real estate | 2023 |
| Roadside Infrastructure Ltd | Construction | 2012 |
| Roadside Real Estate PLC | Construction | 2010 |
| Roadside Reit Limited | Professional & scientific | 2023 |
| Robbie Dunne Racing Limited | Arts & recreation | 2019 |
| Robert Green Ltd | Professional & scientific | 2019 |
| Robert Pooley Limited | Real estate | 1971 |
| Robert Stronge Racing Limited | Real estate | 2003 |
| Robert Viglasky Photography Limited | Information & communication | 2015 |
| Rocketfuel Creative Limited | Information & communication | 2016 |
| Rockhopper Brewing Company Ltd | Manufacturing | 2025 |
| Rockwell END Limited | Construction | 2005 |
| Rohan Ventures Ltd | Real estate | 2024 |
| Rollinson Property Services Ltd | Construction | 2015 |
| Root Steady Ltd | Education | 2019 |
| Rose Wellbeing Generation CIC | Health & social care | 2021 |
| Rosemount Gresham Limited | Construction | 2011 |
| Rosier Racing Ltd | Professional & scientific | 2024 |
| Ross Brooke Estate Planning LLP | | 2016 |
| Ross Coakley Racing Ltd | Arts & recreation | 2022 |
| Rossa Ryan Limited | Arts & recreation | 2020 |
| ROT90S Ltd | Arts & recreation | 2025 |
| Rotorcraft Operations Limited | Professional & scientific | 2010 |
| Round Here Artist Management Ltd | Arts & recreation | 2024 |
| Round Table Limited (the) | Education | 1939 |
| Royal Wootton Bassett Racing Limited | Arts & recreation | 2019 |
| RPS Trustees Limited | Other services | 1993 |
| RR Elite Limited | Transport & logistics | 2011 |
| Ruby B Ltd | Hospitality | 2018 |
| Ruckus Engineering Limited | Arts & recreation | 2016 |
| Rugrat Developments Ltd | Construction | 2025 |
| Ruiseal Consulting Limited | Administrative & support | 2025 |
| Rumbolds Limited | Agriculture & fishing | 1983 |
| Runtimo Limited | Wholesale & retail | 2026 |
| Rush Tutors Ltd | Education | 2023 |
| Rusway Ltd | Transport & logistics | 2025 |
| Ryan Cripps Carpentry Ltd | Construction | 2023 |
| Rydberg Engineering UK Ltd | Professional & scientific | 2025 |
| Ryde Digital Ltd | Professional & scientific | 2025 |
| Rydermarsh Ocaid Limited | Information & communication | 1998 |
| S & J Haulage Ltd | Transport & logistics | 2020 |
| S & K Partners Ltd | Hospitality | 2026 |
| S Andrade Psychology Limited | Health & social care | 2025 |
| S Consulting Limited | Professional & scientific | 2017 |
| S D Jones & SON Limited | Wholesale & retail | 2019 |
| S Lloyd Construction Ltd | Construction | 2026 |
| S P Wilkinson Engineering Ltd | Professional & scientific | 2012 |
| S R Williams & Sons Limited | Wholesale & retail | 2002 |
| S&S Building Construction Ltd | Construction | 2018 |
| S&T Wholesale Limited | Wholesale & retail | 2012 |
| S-Cubed Biometrics Limited | Administrative & support | 2011 |
| S. Karger Publishers Ltd | Information & communication | 1996 |
| S.J.Wharton Limited | Wholesale & retail | 1942 |
| Sabespoke Ltd | Professional & scientific | 2025 |
| Safari Star Ltd | Wholesale & retail | 2019 |
| Safe SFX Ltd | Information & communication | 2017 |
| Safer Site Solutions Ltd | Public administration | 2020 |
| Saferwaters Limited | Professional & scientific | 2024 |
| Safeswitch Electrical Services Ltd | Construction | 2018 |
| Safety Fast! Limited | Professional & scientific | 2010 |
| Safety Zone Limited | Professional & scientific | 2012 |
| Saffkit Limited | Other services | 2026 |
| Saficon Tech Limited | Wholesale & retail | 2020 |
| Sailors Breeze Ltd | Manufacturing | 2021 |