| Avenista | Cheshire |
| Aventus Platform Ltd | |
| AVEVA Group plc | Cambridgeshire |
| Avexia | Hampshire |
| AviadoBio Ltd | |
| AviaSoft Ltd | Greater London |
| AVID plc | East Sussex |
| Avida Global Ltd | |
| Avieco | |
| Avillion, LLP | |
| Avipero Ltd | |
| Aviva | Greater London |
| Avizent Network Solutions | |
| Avnio | |
| Avon Computer Co-operative Ltd | Wiltshire |
| Avon Data | |
| Avonline Networks | |
| Avontus Software Corporation | Cambridgeshire |
| Avonwood Developments Ltd | Dorset |
| Avora | Greater London |
| Avrion | Hertfordshire |
| avrmobiles.co.uk Ltd | Hertfordshire |
| AVUXI | Greater London |
| AW Marketing (AWARE) Ltd | Cornwall |
| Awaken Learning Ltd | |
| Aware Digital | |
| Awareness Software Ltd | Greater Manchester |
| AWD-IT | Staffordshire |
| AWE Europe Ltd | Surrey |
| AWK Computers Ltd | Greater Manchester |
| awmedia.marketing Ltd | |
| AWS Electronics Group Ltd | Staffordshire |
| AX Software Ltd | |
| Axcess IT | |
| Axia Consulting Ltd | Kent |
| AXIA Management Services Ltd | |
| Axial Capital Partners | |
| Axial Systems Ltd | Berkshire |
| Axial3D | |
| Axicon Auto ID Ltd | Oxfordshire |
| Axiologik Ltd | West Yorkshire |
| Axiom Internet Group Ltd | Greater Manchester |
| Axiom Manufacturing Services Ltd | Caerphilly |
| Axiom.ai | |
| Axiomise Ltd | |
| Axios | Edinburgh |
| AXIS (Milton) Ltd | Cambridgeshire |
| Axis Bank ltd | |
| Axis-Shield Diagnostics Ltd | |
| Axisfirst | Somerset |