| AI Property 1 Ltd | Real estate | 2020 |
| AI Property Intelligence Ltd | Information & communication | 2025 |
| AI Supply Ltd | Wholesale & retail | 2025 |
| AI Trading 2 Ltd | Hospitality | 2020 |
| AI Tyres Ltd | Wholesale & retail | 2025 |
| AI Wealth Partners Ltd | Professional & scientific | 2025 |
| AI1122 Associates Ltd | Professional & scientific | 2021 |
| Aiaia Limited | Financial services | 2020 |
| Aias Recruitment Ltd | Administrative & support | 2014 |
| Aicom Solar Consult Limited | Information & communication | 2025 |
| AID Clinical Ltd | Extraterritorial | 2021 |
| Aide Automotive Limited | Manufacturing | 2003 |
| Aidy Electrical Ltd | Construction | 2018 |
| Aiello Properties Ltd | Real estate | 2024 |
| Aigns Limited | Wholesale & retail | 2026 |
| Aikaterini Sarantopoulou Limited | Health & social care | 2017 |
| AIM Direct Ltd | Wholesale & retail | 2025 |
| AIM High Maths Education Limited | Education | 2021 |
| AIM Property Consultancy Ltd | Professional & scientific | 2022 |
| AIM Surveying Limited | Professional & scientific | 2021 |
| AIM3 Ltd | Information & communication | 2025 |
| Aima Bokhari Limited | Wholesale & retail | 2025 |
| Aimam Group Ltd | Wholesale & retail | 2023 |
| Aimee Hamilton Limited | Wholesale & retail | 2017 |
| Aimee Smith Permanent Cosmetics Limited | Other services | 2017 |
| AIN Watches Limited | Wholesale & retail | 2021 |
| Ainsley Asphalt Holdings Ltd | Financial services | 2026 |
| Ainsley Asphalt Ltd | Construction | 2018 |
| Ainsley Fencing and Landscaping Ltd | Construction | 2018 |
| AIO Plumbing & Heating Solutions Ltd | Construction | 2024 |
| Aipi Solutions Ltd | Information & communication | 2023 |
| Air 27 Air Conditioning Installation London Ltd | Energy | 2026 |
| Air 66 Design Limited | Professional & scientific | 2018 |
| Air Communications Limited | Information & communication | 2023 |
| Air IT Group Limited | Information & communication | 2005 |
| Air Kings Ltd | Arts & recreation | 2015 |
| Air Movement & Fabrications Ltd | Manufacturing | 2013 |
| Air Quality Solutions Ltd | Professional & scientific | 2022 |
| Air Supply Skydiving Limited | Arts & recreation | 1989 |
| Air Transfer Systems Ltd | Construction | 2007 |
| Aircrew Training Ltd | Administrative & support | 2023 |
| Aircus Land Limited | Real estate | 2019 |
| Aire Content Loft Limited | Professional & scientific | 2025 |
| Aire Rentals Ltd | Hospitality | 2026 |
| Aire Salon Limited | Other services | 2025 |
| Aire Vocational Training Limited | Education | 2011 |
| Airflex Investments Limited | Financial services | 2024 |
| Airflex Roto Ltd | Manufacturing | 2025 |
| Airgen IT Limited | Information & communication | 2022 |
| Airmac UK Ltd | Energy | 2014 |
| Airmotiv Ltd | Manufacturing | 2019 |
| Airport Bearing Company Limited | Extraterritorial | 2024 |
| Airport Carriages Ltd | Transport & logistics | 2023 |
| Airport Lift UK Ltd | Transport & logistics | 2025 |
| Airport Terminal Transfers Ltd | Transport & logistics | 2019 |
| AIRPORT24X7 Limited | Administrative & support | 2017 |
| Airvend UK Limited | Wholesale & retail | 2008 |
| Airways Heating Limited | Construction | 1967 |
| Airwise Ltd | Manufacturing | 2011 |
| Airworthiness Assured Limited | Extraterritorial | 2011 |
| Aisle SIX Ltd | Wholesale & retail | 2025 |
| Aisrah Cars Ltd | Administrative & support | 2026 |
| Aisrah Real Estate Ltd | Real estate | 2025 |
| AIT Property Ltd | Real estate | 2024 |
| Aiyana Solutions Ltd | Information & communication | 2026 |
| Aizaha Transport Limited | Transport & logistics | 2021 |
| Aizalarslan Ltd | Wholesale & retail | 2024 |
| Aizio Associates Ltd | Professional & scientific | 2017 |
| Aizpuru Oral Health Care Ltd | Health & social care | 2026 |
| AJ & SJ Developers Limited | Construction | 2014 |
| AJ & Sons (UK) Limited | Extraterritorial | 2012 |
| AJ Auto Access Ltd | Administrative & support | 2025 |
| AJ Barber Nottingham Ltd | Other services | 2025 |
| AJ Building Maintenance UK Limited | Construction | 2019 |
| AJ Fire Protection Limited | Public administration | 2023 |
| AJ Goody's Ltd | Hospitality | 2023 |
| AJ Heat & Plumb Ltd | Construction | 2020 |
| AJ Humphrey Forestry and Land Management Ltd | Agriculture & fishing | 2024 |
| AJ International Procurement Limited | Wholesale & retail | 2026 |
| AJ Northern Group Ltd | Professional & scientific | 2021 |
| AJ Performance & Motorsport Ltd | Wholesale & retail | 2026 |
| AJ Project Consultancy Limited | Administrative & support | 2022 |
| AJ Sport Football Club CIC | Education | 2025 |
| Aj&L Logistics Ltd | Administrative & support | 2017 |
| Aj's Cafe Giltbrook Ltd | Hospitality | 2025 |
| Aj-Casim Limited | Health & social care | 2019 |
| AJ15 Ltd | Hospitality | 2024 |
| AJA Builders Ltd | Construction | 2014 |
| Ajaes COB Shop Ltd | Hospitality | 2021 |
| AJB Flooring (Nottingham) Limited | Wholesale & retail | 2020 |
| AJB Nottingham Ltd | Transport & logistics | 2022 |
| AJB Percussion Tuition Ltd | Education | 2003 |
| AJB Property Group Ltd | Real estate | 2024 |
| AJD Electrical and PAT Testing Services Ltd | Manufacturing | 2015 |
| AJE Assessments and Services Ltd | Health & social care | 2024 |
| AJE Property Holdings Limited | Real estate | 2022 |
| AJF1 Limited | Real estate | 2021 |
| AJF2 Limited | Professional & scientific | 2025 |
| Ajfa Properties Limited | Construction | 2019 |
| AJG Telecoms Ltd | Information & communication | 2026 |