| AG Engineering and Survey Ltd | Professional & scientific | 2018 |
| AG Fraser Limited | Construction | 2018 |
| AG Realty Ltd | Real estate | 2025 |
| Ag&Pg Ltd | Administrative & support | 2020 |
| AGA Transport Logistics Ltd | Transport & logistics | 2023 |
| Agassiz Engineering Ltd | Administrative & support | 2014 |
| Agastya Properties Limited | Real estate | 2017 |
| Agbarha People Consulting Ltd | Administrative & support | 2013 |
| Agbiotec Ltd | Wholesale & retail | 2021 |
| AGD Solutions Limited | Information & communication | 2007 |
| AGE Solar Limited | Construction | 2023 |
| Agency Central Ltd | Administrative & support | 2000 |
| Agenda Project Management Limited | Professional & scientific | 2024 |
| AGI Pipeline Services Ltd | Professional & scientific | 2026 |
| Agile Business Transformations Limited | Professional & scientific | 2017 |
| Agile Ways of Working Limited | Information & communication | 2026 |
| Agility Consultancy Services Limited | Other services | 2017 |
| Agility Property Services Limited | Real estate | 2019 |
| Agitruck Ltd | Transport & logistics | 2023 |
| AGJ Surgical Limited | Administrative & support | 2016 |
| AGK Holdings Ltd | Information & communication | 2019 |
| Agnes Black Limited | Professional & scientific | 2024 |
| Agnew Associates Ltd | Professional & scientific | 2023 |
| Agot Global Synergies Limited | Professional & scientific | 2023 |
| AGR Electrical (North West) Limited | Construction | 2016 |
| Agrb Consulting Ltd | Information & communication | 2019 |
| AGS Berlin Limited | Administrative & support | 2007 |
| AGS Civil Solutions Limited | Professional & scientific | 2017 |
| AGS SON Limited | Transport & logistics | 2026 |
| AGT Network Limited | Transport & logistics | 2024 |
| AH Engineering Consulting Limited | Professional & scientific | 2018 |
| AH KF Ltd | Real estate | 2025 |
| AH Project Services Ltd | Administrative & support | 2026 |
| AH Supply Chain Limited | Other services | 2018 |
| Ahadex Ltd | Wholesale & retail | 2026 |
| Ahead of the Game Consultancy Services Ltd | Professional & scientific | 2024 |
| Ahhr Demir Ltd | Wholesale & retail | 2024 |
| Ahja Properties Limited | Real estate | 2023 |
| AHL Anglia Limited | Professional & scientific | 1996 |
| Ahmed Farag Limited | Health & social care | 2013 |
| Ahmed Testing Limited | Information & communication | 2018 |
| Ahpm Holdings Ltd | Financial services | 2019 |
| AI Android & IOS Services Ltd | Administrative & support | 2026 |
| AI Educate Ltd | Administrative & support | 2024 |
| AI Electrical Solutions Limited | Construction | 2016 |
| AI Engineering Consultancy Limited | Administrative & support | 2015 |
| AIB Estates Ltd | Real estate | 2024 |
| Aiday Ltd | Professional & scientific | 2020 |
| Aidblanket Community Interest Company | Financial services | 2025 |
| AIF Industries Ltd | Administrative & support | 2022 |
| Aimei Limited | Wholesale & retail | 2024 |
| Aimhub Ltd | Financial services | 2015 |
| AIO Engineering Services Ltd | Professional & scientific | 2022 |
| Air Compressors & Tools Ltd | Other services | 1920 |
| Air Jing Services Limited | Administrative & support | 2010 |
| Air Power Ltd | Wholesale & retail | 2021 |
| Airframe Stress Solutions Limited | Professional & scientific | 2018 |
| Airnell Ltd | Professional & scientific | 2017 |
| Airnell Properties Limited | Real estate | 2018 |
| Airobotic Systems Limited | Professional & scientific | 2025 |
| Airwell Measurements Limited | Professional & scientific | 1990 |
| AIS Delivery Ltd | Transport & logistics | 2022 |
| AIS Installation Team Ltd | Transport & logistics | 2022 |
| AIS Logistics NW Ltd | Transport & logistics | 2025 |
| Aisavalyn Ltd | Administrative & support | 2025 |
| Aitch TEE Consulting Limited | Professional & scientific | 2020 |
| Aitch Testing Ltd | Administrative & support | 2025 |
| Aitchison Cleaning Services Limited | Administrative & support | 2023 |
| Aitchison Holding Company Ltd | Financial services | 2023 |
| Aitchison Logistics Service Ltd | Transport & logistics | 2020 |
| Aitchison Vehicle Services Ltd | Administrative & support | 2023 |
| Aitken Consulting Ltd | Professional & scientific | 2022 |
| AJ Bespoke Lettings Ltd | Households | 2025 |
| AJ Box Ltd | Wholesale & retail | 2024 |
| AJ Design Dynamics Limited | Professional & scientific | 2023 |
| AJ Engineering Consultancy Ltd | Professional & scientific | 2023 |
| AJ Housing Group Limited | Real estate | 2024 |
| AJ Nicko Ltd | Transport & logistics | 2014 |
| AJ Prime Ltd | Administrative & support | 2026 |
| AJ Systems Europe Ltd | Wholesale & retail | 2012 |
| AJ Technology Limited | Information & communication | 2006 |
| Ajax Buckham Ltd | Information & communication | 2016 |
| AJB Lowton OFF Licence Ltd | Wholesale & retail | 2025 |
| AJC Digital Limited | Information & communication | 2018 |
| AJC Maintenance Services Ltd | Administrative & support | 2006 |
| AJC Tech Solutions Ltd | Information & communication | 2017 |
| AJE Homes Ltd | Households | 2022 |
| AJE Property Developments Ltd | Real estate | 2019 |
| AJF Management Ltd | Professional & scientific | 2026 |
| AJG 2020 Consulting Limited | Administrative & support | 2015 |
| AJH Design Engineering Limited | Administrative & support | 2008 |
| AJH Grid Consultancy Ltd | Administrative & support | 2025 |
| Ajhazell Ltd | Professional & scientific | 2019 |
| Ajhm Consulting Limited | Information & communication | 2020 |
| AJK HR Limited | Administrative & support | 2019 |
| AJL Systems Management Ltd | Professional & scientific | 2022 |
| AJM Analytics Ltd | Administrative & support | 2019 |
| AJM Commercial Services Ltd | Administrative & support | 2024 |
| AJM Contract Consulting Limited | Administrative & support | 2015 |
| AJM Dunamis Limited | Professional & scientific | 2025 |