| Jabmo | |
| Jacarta Ltd | |
| Jack Denning | West Midlands |
| Jackie Jeromson | |
| Jackson Hammond | |
| JacksonBone Ltd | East Sussex |
| Jacquard Group Ltd | |
| JafSoft Ltd | Greater Manchester |
| Jag Media | |
| Jagex Ltd | Cambridgeshire |
| Jago Consultants | |
| Jahi Laptops Ltd | |
| Jalco Ltd | Suffolk |
| Jaltek | Bedfordshire |
| JAM Creative Marketing Ltd | |
| James Adams Creative Design | Greater Manchester |
| James Andrews Recruitment Solutions | |
| James Peter Cooper | Somerset |
| James Spiegel & Co | |
| James Stanley | |
| Jamie's Computers | |
| Jammy Digital | Greater Manchester |
| Jan Klin & Associates Ltd | Conwy |
| Jandu Technologies Ltd | Shropshire |
| Janes | |
| Janus Henderson Investors | |
| Jarilo Design | |
| Jaro.dev | |
| Jarret & Lam Ltd | Surrey |
| JarvisTech Ltd | East Sussex |
| Jask Creative | West Midlands |
| Jasmin Media | |
| JAT Web Design | Somerset |
| Javelin Payments UK Ltd | South Yorkshire |
| Jaw Drop Games Ltd | |
| JAX Internet Ltd | |
| Jay by Jay Software | Cumbria |
| Jaywing plc | South Yorkshire |
| Jaywood | |
| JB Communications Ltd | |
| JB Web Development Ltd | |
| jbandg | Warwickshire |
| JBC Skills Training | West Midlands |
| JBH Consulting | West Midlands |
| JBi Digital | |
| JBS Group Scotland Ltd | |
| JC Applications Development Ltd | Hampshire |
| JC Designs Ltd | Essex |
| JCD Computers | Northamptonshire |
| JCM Business Solutions | |