| iDeveloperNetwork | Berkshire |
| Idexo | |
| Idhammar Systems | |
| IDHL | Greater Manchester |
| idibu | |
| IDL Systems Ltd | Derbyshire |
| IdleServ Ltd | Essex |
| IDNet | Hertfordshire |
| Idox plc | Berkshire |
| IDS Indata | |
| IDS Logic UK Ltd | |
| IDT Ltd | Derbyshire |
| IDTechEx Ltd | Cambridgeshire |
| Iduna | |
| IDX | |
| iDynamics Ltd | West Yorkshire |
| IE Brand | |
| IE Digital | |
| iebSoftware | Derry and Strabane |
| IEEE International Conference on Robotics and Automation | Greater London |
| ievo Ltd | Tyne and Wear |
| IEW Ltd | Wiltshire |
| IF Consultancy | |
| If u cant find it | |
| If You Could Jobs | |
| If6was9design Ltd | Essex |
| iFastNet Ltd | Tyne and Wear |
| IFB Aberdeen | Aberdeen |
| IFG Consulting Ltd | |
| ifixdrupal.co.uk | Berkshire |
| iFixTech | |
| Iflow | West Midlands |
| iForge Ltd | Greater London |
| Iformis Ltd | Edinburgh |
| ifour | Kent |
| IG Smart Ltd | |
| Igaware Ltd | Tyne and Wear |
| iGears Ltd | |
| Igence Software Ltd | West Sussex |
| Igentics Ltd | Cambridgeshire |
| Igloo | |
| IGLU Network Ltd | |
| Ignite | |
| Ignite Data | |
| Ignite IT | Lisburn and Castlereagh |
| Ignite North East | |
| Ignite SEO | |
| Ignite Software Systems Ltd | |
| Ignite Systems Ltd | Cheshire |
| Ignitec Ltd | |