| React Computer Partnership | Suffolk |
| React Native Development Company | |
| Reactec Ltd | |
| Reactive Graphics | |
| Reactive Graphics Ltd | |
| Reactor15 Ltd | Devon |
| ReactWay | |
| Reading Computers | Berkshire |
| Reading Room | |
| Ready Steady Go SEO | |
| ReadyGo Diagnostics | |
| Readynez | |
| Readysalted | |
| ReadyWeb | Berkshire |
| Real Agency | |
| Real Code Ltd | |
| Real Electronics | South Yorkshire |
| Real Fast Reports Ltd | |
| Real Time Web Solutions | South Yorkshire |
| Real Wireless Ltd | |
| Realeyes | |
| Realife Tech | |
| Realised Realities Ltd | |
| Realising Designs Ltd | Kent |
| Realities Centre | |
| Reality Games (London) Ltd | |
| Reality in Virtual Reality Ltd | |
| Reality Solutions | |
| Realityhouse | Somerset |
| RealityLab: London | Greater London |
| RealityMine Ltd | Greater Manchester |
| Really Effective | West Yorkshire |
| Really Simple Systems | Hampshire |
| Really Useful Computer Company | Northamptonshire |
| Really Useful Websites Ltd | Cheshire |
| Realmac Software Ltd | East Sussex |
| Realnet Ltd | Cambridgeshire |
| RealSense Solutions Ltd | Derbyshire |
| RealTime Control Systems Ltd | Hertfordshire |
| RealVNC | Cambridgeshire |
| Reaper Telecom | Cambridgeshire |
| Reapit | |
| Reath Technology Ltd | |
| Reation Engines | |
| Rebel & Slaughter Ltd | Bristol |
| Reboot and Repair | East Sussex |
| Reboot Online Marketing Ltd | |
| Reboot Systems Ltd | Norfolk |
| Recast | |
| Recenseo Ltd | |