| AW Marketing (AWARE) Ltd | Cornwall |
| Awaken Learning Ltd | |
| Aware Digital | |
| Awareness Software Ltd | Greater Manchester |
| AWD-IT | Staffordshire |
| AWE Europe Ltd | Surrey |
| AWESEM | |
| Awesome Creative | |
| 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 | |
| Axians | |
| Axicon Auto ID Ltd | Oxfordshire |
| Axiologik Ltd | West Yorkshire |
| Axiom Internet Group Ltd | Greater Manchester |
| Axiom Manufacturing Services Ltd | Caerphilly |
| Axiom Online | |
| Axiom.ai | |
| Axiomise Ltd | |
| Axios | Edinburgh |
| AXIS (Milton) Ltd | Cambridgeshire |
| Axis-Shield Diagnostics Ltd | |
| Axisfirst | Somerset |
| AxisStars | |
| Axisway | Somerset |
| Axisway Ltd | |
| Axitech Group Ltd | |
| Axle Energy Ltd | |
| Axol Bioscience Ltd | |
| Axon IT | |
| Axons | |
| Axovia Therapeutics | |
| AXP Web Design | West Lothian |
| AY | |
| AYA Ventures | |
| Aylesbury Automation Ltd | |
| Aylesbury Web Design | Buckinghamshire |
| Ayo Telecom Ltd | |
| Ayoa | Vale of Glamorgan |
| Ayora Technologies Ltd | |
| Ayrshire College | |
| Ayrshire Web Design | |
| Ayup Creative Ltd | |