| 3tc Software | Leicestershire |
| 3W Design | Bristol |
| 3wise Digital | Surrey |
| 4 Earth Intelligence | |
| 4-wardloop Design | East Sussex |
| 44 Web Design | West Midlands |
| 499Designs | Greater Manchester |
| 49th Floor Design & Artworking | |
| 4basebio plc | |
| 4C Creatives | South Yorkshire |
| 4C Strategies Ltd | Leicestershire |
| 4CM | |
| 4Com plc | Dorset |
| 4D Solutions Ltd | Buckinghamshire |
| 4D Web Designs | |
| 4fx Design & Multimedia Ltd | Buckinghamshire |
| 4gRural.co.uk | |
| 4ICG | Glasgow |
| 4Links Ltd | Buckinghamshire |
| 4mat Digital Solutions | Lancashire |
| 4Mation Educational Resources Ltd | Devon |
| 4S DAWN Clinical Software | Cumbria |
| 4s Systems Ltd | |
| 4S Webs | Greater Manchester |
| 4Secure Ltd | Northamptonshire |
| 4t Niagara Software | Gloucestershire |
| 4TailConnections | Essex |
| 4tel Communications Ltd | Cornwall |
| 4xxi Software Ltd | |
| 5 Star & Co | |
| 505 Games Ltd | Buckinghamshire |
| 55 Web Design Edinburgh | Edinburgh |
| 56 Degrees | Greater London |
| 5874 Commerce | West Midlands |
| 5c Services Ltd | Powys |
| 5G Communications Ltd | Buckinghamshire |
| 5Mins AI Ltd | |
| 5RV Digital | |
| 5th Utility Ltd | Derbyshire |
| 5wire Networks Ltd | Greater London |
| 60sec.site | |
| 64 Studio Ltd | Isle of Wight |
| 64Digital | Greater London |
| 65bit Software Ltd | West Midlands |
| 69 drops studios | |
| 6B | West Yorkshire |
| 6EP | |
| 6point6 Ltd | Greater London |
| 6rs | |
| 72 Capital Ltd | |