| Azad University (IR) in Oxford Ltd | |
| Azeus UK Ltd | |
| Azexis | Suffolk |
| AZKY Tech Labs | |
| AZO Robotics | |
| Azolve Ltd | Glasgow |
| Azoncode Ltd | |
| AZoOptics.com | Greater Manchester |
| Aztec | |
| Aztec Internet | |
| Aztec IT Ltd | Essex |
| Aztec Media | |
| Aztech MicroCentres | Berkshire |
| AZTechIT | |
| AzteQ Solutions Ltd | Hertfordshire |
| Azul Optics | |
| Azura Group Ltd | Essex |
| Azuri Technologies Ltd | |
| Azzure IT Ltd | South Yorkshire |
| Azzurro | |
| B-Plan Information Systems | Hampshire |
| B-Secur | |
| B-StartUps | |
| B.A. Collins Computer Software | Greater London |
| B.S.S.B. | Surrey |
| B1 Creative | |
| B13 AI Ltd | |
| B13 Technology | Greater London |
| B2B IT Ltd | Greater Manchester |
| B2B Store | |
| B2C2 | |
| B2k Computers | |
| B2Space Ltd | |
| B9Lab | |
| b:web Ltd | Surrey |
| BAAAM | |
| Babel Interactive | Worcestershire |
| BabelStone | |
| Babraham Institute | |
| BAC Pro | East Sussex |
| BACB | |
| Back That Up | Greater Manchester |
| Backed, LLP | Greater London |
| Backendz | |
| BackFuture | |
| Background Marketing | |
| Backseatz | |
| Backslash Build Ltd | Somerset |
| Backup Technology Ltd | West Yorkshire |
| Bacra Ltd | |