| AIG Tech Solution | |
| AilseVax | |
| AIM Internet Ltd | West Midlands |
| Aimes Grid Services Ltd | Merseyside |
| Aimondo | |
| Aindale Business and Technology Ltd | West Yorkshire |
| Ainostics | |
| aiPDF | |
| Air | West Midlands |
| Air 66 Design Ltd | |
| Air Control Entech | |
| Air Design Ltd | |
| Air IT | Derbyshire |
| Air Web Solutions | Greater London |
| Aira Digital Ltd | |
| Airangel Ltd | |
| AirBlade Software Ltd | |
| Airbyte Digital Ltd | |
| Aircards Studio | |
| Aire Global Ltd | |
| Aire Logic Ltd | |
| Airedale Computers | |
| AireWeb | West Yorkshire |
| Airfinity Ltd | |
| AIRPA Research & Development | |
| Airparks Services Ltd | |
| Airport Information Systems Ltd | Nottinghamshire |
| AirPortr | |
| Airship Services Ltd | |
| Airsource Ltd | Cambridgeshire |
| Airsys Communications Technology Ltd | Hampshire |
| Airtechnics Ltd | |
| Airtel Africa plc | |
| Airtel-Vodafone | |
| Airtime Rewards Ltd | |
| Airwave Europe Ltd | West Sussex |
| Airwave Solutions Ltd | |
| Airwer Ltd | County Durham |
| Aiviq Ltd | |
| AJ Bell | |
| AJ Computing | Lincolnshire |
| AJ New Media | Derbyshire |
| Aj-creativedesigns | |
| AJC Software | Lincolnshire |
| AJM Automation Ltd | Derbyshire |
| AJP IT Services | Bristol |
| AJR Data Recovery Services | Wiltshire |
| AKA Internet Ltd | |
| AKA Media Bolton Website Design Co. | Greater Manchester |
| Akamis Bio | |