| Applied Concepts Limited | Information & communication | 1989 |
| Applied Ecology Ltd | Professional & scientific | 2005 |
| Applied Intelligent Building Limited | Other services | 2002 |
| Applied Knowledge Limited | Administrative & support | 2009 |
| Applied Microbiology International | Other services | 2008 |
| Applied Protection Guards Limited | Manufacturing | 2014 |
| Applied Psychology Solutions Limited | Other services | 2012 |
| Applied Thermal Control Limited | Manufacturing | 1995 |
| Applied Time Sciences Limited | Manufacturing | 2025 |
| Applisco Ltd | Education | 2026 |
| Appnovate Limited | Information & communication | 2026 |
| Appsherpas Limited | Information & communication | 1998 |
| Appsubhub Limited | Information & communication | 2026 |
| Appwox Limited | Information & communication | 2016 |
| Apricity Dreams Co Ltd | Manufacturing | 2021 |
| Apricity Solutions Limited | Professional & scientific | 2024 |
| April Business Centres Limited | Real estate | 2026 |
| Aprim Ltd | Wholesale & retail | 2025 |
| Apriori Limited | Information & communication | 2014 |
| Apropos AI Limited | Information & communication | 2023 |
| APS Foxton Ltd | Real estate | 2025 |
| Apsley Court (Crowthorne) Management Company Limited | Households | 2005 |
| APT Resources Limited | Education | 2017 |
| Apta Cambridge Ltd | Information & communication | 2024 |
| Aptapp Limited | Information & communication | 2014 |
| Aptitude Agency Ltd. | Professional & scientific | 2009 |
| Apto Consulting Limited | Professional & scientific | 2004 |
| Aptology Limited | Health & social care | 2001 |
| Apun Limited | Professional & scientific | 2021 |
| Aqdot Limited | Manufacturing | 2012 |
| Aqeeli Limited | Health & social care | 2024 |
| Aqpt Limited | Professional & scientific | 2020 |
| Aqua Linea Developments Ltd | Construction | 2020 |
| Aqua Sail Consultants Limited | Professional & scientific | 2019 |
| Aqua-Tech and Landscapes Limited | Administrative & support | 2023 |
| Aquaid (UK) Ltd | Extraterritorial | 2005 |
| Aquamw LLP | | 2010 |
| Aquasium Limited | Manufacturing | 1995 |
| Aquasium Technology Limited | Manufacturing | 2001 |
| Aquastream Water Softeners Ltd | Water & waste | 2011 |
| Aquataura Swimming Limited | Education | 2015 |
| Aquawood Ltd | Manufacturing | 2025 |
| Aquaxprs Ltd | Agriculture & fishing | 2015 |
| Aquila Investments Limited | Agriculture & fishing | 1991 |
| Aquilegia Accounting Limited | Professional & scientific | 2019 |
| Aquivar Management Services Limited | Extraterritorial | 1983 |
| AR Aero Ltd | Manufacturing | 2024 |
| AR Imaging Ltd | Health & social care | 2019 |
| AR Student Stays Limited | Real estate | 2025 |
| ARA Biosciences Consulting Limited | Professional & scientific | 2021 |
| Araab Management Ltd | Professional & scientific | 2020 |
| Araarah Limited | Manufacturing | 2025 |
| Araby Property Developments Ltd | Construction | 2020 |
| Arade BIO Ltd | Professional & scientific | 2024 |
| Arak Ltd | Professional & scientific | 2019 |
| Aralbest Limited | Extraterritorial | 1982 |
| Aras Grill Ltd | Hospitality | 2026 |
| Aras Trade Ltd | Wholesale & retail | 2023 |
| Araxr Ltd | Professional & scientific | 2022 |
| Arbantia Limited | Construction | 2007 |
| Arbor Close Management Company Limited | Households | 2020 |
| Arbor Mediation Limited | Other services | 2025 |
| Arboretum Cafe Ltd | Hospitality | 2008 |
| Arbury Motorist Centre | | 1988 |
| ARC Reserves Ltd | Administrative & support | 2010 |
| ARC Transport Ltd | Transport & logistics | 2026 |
| Arcadia Court 2 RTM Company Limited | Households | 2016 |
| Arcadia Court RTM Company Limited | Households | 2011 |
| Arcadia Management Company Limited | Households | 2023 |
| Arcadia Three Management Company Limited | Households | 2025 |
| Arcadia Two Management Company Limited | Households | 2025 |
| Arccona Limited | Professional & scientific | 2011 |
| Arch Building Services Limited | Construction | 2021 |
| Arch Common Land Limited | Extraterritorial | 2011 |
| Arch Sourcing Ltd | Real estate | 2019 |
| Archangel Architects Ltd | Professional & scientific | 2019 |
| Archangel Brewing Ltd. | Manufacturing | 2014 |
| Archangel Limited | Professional & scientific | 2000 |
| Arche Consulting International Limited | Professional & scientific | 2020 |
| Archer Power Services Ltd | Construction | 2026 |
| Archidemand Limited | Information & communication | 2018 |
| Archie Rogers Limited | Other services | 2009 |
| Archineers Limited | Professional & scientific | 2000 |
| Archinesture Solutions Ltd | Construction | 2025 |
| Archipel&Co Ltd | Professional & scientific | 2021 |
| Archipelago Consulting Ltd | Extraterritorial | 2012 |
| Archipelago Sands Ltd | Financial services | 2020 |
| Archipelago Technology Group Ltd | Professional & scientific | 2012 |
| Architectural Armour Limited | Professional & scientific | 2009 |
| Architectural Glazing Installations (Cambridge) Ltd | Administrative & support | 2014 |
| Archstone Partners Ltd | Real estate | 2015 |
| Archway Court Freehold Limited | Real estate | 2005 |
| Archway Court Residents Society Limited | Professional & scientific | 1971 |
| Arctic Alliance Limited | Professional & scientific | 2014 |
| Arctran Corporation Limited | Information & communication | 2014 |
| Arctran Holdings Limited | Information & communication | 2014 |
| Arcus Global Limited | Public administration | 2009 |
| Ardea Biosciences Limited | Professional & scientific | 2008 |
| Ardent Ventures Limited | Professional & scientific | 2026 |
| Ardtarmon Search Limited | Professional & scientific | 2017 |