| Inertia Game Studios | Cambridgeshire |
| iNet Ventures Ltd | |
| iNetdigital | |
| INetLab Ltd | Devon |
| Inevitable Ltd | |
| InferSens Ltd | |
| Infex Therapeutics Ltd | |
| Infigo Software Ltd | West Sussex |
| Infiled EM International | |
| Infineum International Ltd | |
| Infinite Eye | Glasgow |
| Infiniti Recycling Ltd | |
| Infinitopes Precision Immunomics | |
| Infinity Business Solutions Ltd | |
| Infinity Metaverse | |
| Infinity Technologies | |
| Infinity3 Ltd | |
| Inflection Point | |
| Inflecto Systems Ltd | South Yorkshire |
| Inflo | |
| Inflowen | |
| Influence Digital | Greater London |
| Influence Ltd | Surrey |
| Influense Design | |
| Influential Computers Ltd | Oxfordshire |
| Influential Software Services Ltd | |
| Infobip Ltd | Greater London |
| Infobo Ltd | East Sussex |
| Infogrid | Greater London |
| Infolink Electronic Systems Ltd | West Midlands |
| Infologic IT | Bedfordshire |
| Infonote Datasystems Ltd | Leicestershire |
| Inforcer Ltd | |
| Inforgen | Scottish Borders |
| Informa | |
| Informa Connect | |
| Informa Connect Ltd | |
| Informa Markets | |
| Informa Tech | |
| Informatics Ventures | Edinburgh |
| Information Age | Greater London |
| Information Commissioner's Office | |
| Information Design Associates | Bedfordshire |
| Information Risk Management | Gloucestershire |
| Information Security Forum Ltd | |
| Information Solutions Ltd | Shropshire |
| InformationWeek | Greater London |
| Informed Choices Consulting | |
| Informed Solutions | Greater Manchester |
| Informit Systems Ltd | Dundee |