| Remtech (Computer Security) Ltd | |
| Remtix | |
| Renaissance Pharma Ltd | |
| Renalytix AI plc | Cardiff |
| Renav Ltd | |
| RenderHeads Ltd | |
| Rendmate | |
| Renegade | |
| Renegade IT Consultants Ltd | Aberdeen |
| ReNeuron Group plc | |
| Renew Creative | |
| Renewable Energy Institute | |
| Renishaw plc | |
| Renovi Hub | |
| Renovos Biologics Ltd | |
| Renovotec | West Yorkshire |
| Rensair Ltd | |
| Rent Chief | |
| Rental Tablets | |
| Rentman Software Ltd | Greater London |
| Rentr Ltd | |
| REO (UK) Ltd | Shropshire |
| Repair Lab Leeds Ltd | West Yorkshire |
| Repair-My-PC Ltd | Surrey |
| RepairsEtc | |
| Repay Solutions | |
| Repayoo | |
| Repeat Digital Ltd | |
| Rephrase | |
| Replan | |
| Replete Media | Staffordshire |
| Replication Centre | Essex |
| Replify | Belfast |
| Report URI Ltd | |
| Reposition UK | |
| Republic Marketing | |
| Republik One | West Dunbartonshire |
| Republiqe | |
| Requisite I.T. Ltd | Nottinghamshire |
| Resay Technologies | |
| rescomp.NET | Greater Manchester |
| research | |
| Research Grid Ltd | |
| ResearchQX | |
| Reserve Apartments | |
| Resident North Ltd | |
| Resident Pro | North Yorkshire |
| Residently | |
| Resilio Ltd | |
| ResMed UK | |