| Uplands | Swansea |
| UpMail | |
| Upment | Greater London |
| Upmind | |
| UppCast | |
| Upperdog | |
| Uppi | Devon |
| UPS Direct Ltd | Shropshire |
| UPS Systems plc | Oxfordshire |
| Upstream Health | |
| Upstream IT Ltd | Edinburgh |
| Upstream Systems | |
| Uptech Ltd | Norfolk |
| Uptic | |
| Uptime App Ltd | |
| Uptime Systems Ltd | |
| UQ Web Design | Wrexham County Borough |
| URA Thrusters Ltd | |
| Urban Chain | |
| Urban Element Design Solutions Ltd | Oxfordshire |
| Urban Foresight Ltd | |
| Urban Hawk Ltd | |
| Urban Haze Ltd | Greater Manchester |
| Urban Intelligence | |
| Urban Media UK Ltd | Buckinghamshire |
| Urban Planet | |
| Urban-Air-Port Ltd | |
| UrbanThings Ltd | Greater London |
| URM Consulting Services Ltd | Berkshire |
| USB Company | |
| USB Now | Northamptonshire |
| USB-FlashDrive.co.uk | Berkshire |
| USB2U | Northamptonshire |
| Use It Computers | |
| Use Passionfruit Ltd | |
| UseGIS Ltd | Devon |
| User Friendly Computing Ltd | |
| User Fusion Ltd | Neath Port Talbot |
| User2 | Edinburgh |
| Userbird | |
| Userfriendly-Devon | Devon |
| Userled Ltd | |
| Usheru | |
| USICgroup | Merseyside |
| Usomo | Tyne and Wear |
| USP Networks Ltd | Essex |
| USP.ai Ltd | |
| ustwo Ltd | |
| Utelly Ltd | |
| Util | |