| InterWeb Solutions | |
| Interweb360 Ltd | |
| Intouch Games Ltd | West Midlands |
| InTouch Software | Greater London |
| InTouch Systems | Norfolk |
| Intoware Ltd | Nottinghamshire |
| IntraBio | |
| Intract Pharma Ltd | |
| Intradev Ltd | East Riding of Yorkshire |
| Intrahost Ltd | East Riding of Yorkshire |
| IntraLAN Group Ltd | Surrey |
| Intralinx | Surrey |
| Intrasource Ltd | East Riding of Yorkshire |
| Intraspin.com | Glasgow |
| Intrepid Security | Surrey |
| Intrface | |
| Intriangle Solutions | |
| Intrinsic Semiconductor Technologies | |
| Introspective | |
| Intruder Systems Ltd | Greater London |
| Intuitech | |
| Intuitiv Ltd | Buckinghamshire |
| Intuitive Ltd | Channel Islands |
| Intunet | |
| intY Ltd | Bristol |
| InVADE International Ltd | Bristol |
| Invenias Ltd | Berkshire |
| InvenireX | |
| Invent Partners Ltd | North Yorkshire |
| Inventio Software Ltd | Suffolk |
| Inventive Creations | Greater Manchester |
| Inventive Hosting | |
| Inventory Management System Ltd | |
| inVentry | |
| Inverness Campus | Highland |
| InverOak | Essex |
| Inverse Quanta | |
| Invertase Ltd | |
| Invest Africa Ltd | |
| Invest in Bradford | |
| Invest in Manchester | |
| Invest in Perth | |
| Invest Northern Ireland | |
| Investec | |
| InvetLab | |
| Invibio Ltd | |
| Invincible Media | |
| Inviqa UK Ltd | Greater London |
| Invisible Vision Ltd | Norfolk |
| Invisio Solutions Ltd | |