| Archime Ltd | Manufacturing | 2017 |
| Archivio Recruitment Ltd | Administrative & support | 2017 |
| Archway Advertising Limited | Information & communication | 2014 |
| Arda Gents Ltd | Other services | 2018 |
| Ardam Limited | Hospitality | 2018 |
| Ardgal Limited | Construction | 2023 |
| Ardleigh Commercial Properties Limited | Financial services | 2018 |
| Ardour P Limited | Administrative & support | 2023 |
| Arealight Limited | Construction | 1986 |
| Ares Electrical Ltd | Energy | 2016 |
| Arete Coach Ltd | Administrative & support | 2021 |
| Arete Properties Limited | Real estate | 2023 |
| Arge Properties Limited | Financial services | 2025 |
| Argyle Stone Limited | Wholesale & retail | 2013 |
| ARI Global Technologies Ltd | Professional & scientific | 2006 |
| ARI Global Technologies UK Ltd | Water & waste | 2021 |
| Ariadne Technologies Ltd | Information & communication | 2015 |
| Aridan Homes and Property Limited | Real estate | 2023 |
| Aries ES Ltd | Professional & scientific | 2026 |
| Arikiflix Consult Limited | Administrative & support | 2021 |
| Ariston U.K. Ltd | Wholesale & retail | 1986 |
| Arjan Retail Limited | Wholesale & retail | 2019 |
| Arjobex Limited | Manufacturing | 1964 |
| ARK Urology London Limited | Health & social care | 2023 |
| Arka Power System Ltd | Professional & scientific | 2026 |
| Armour Roofing Ltd | Construction | 2015 |
| Armoured Automobiles Limited | Wholesale & retail | 2025 |
| Armstrong Scaffolding Ltd | Construction | 2023 |
| Arnali Events Limited | Arts & recreation | 2023 |
| Arnaut Collective Ltd | Other services | 2025 |
| Arnex Surveying Ltd | Professional & scientific | 2025 |
| Aroma Inn Limited | Hospitality | 2013 |
| Arora Advisory Partners Ltd | Professional & scientific | 2026 |
| Arora Tutors Limited | Education | 2024 |
| Around London City Ltd | Transport & logistics | 2025 |
| Around the Clock Solutions Ltd | Construction | 2022 |
| ARP Builders Limited | Construction | 2026 |
| ARS Doors & Joinery Ltd | Wholesale & retail | 2020 |
| Arsenal Medical Ltd | Health & social care | 2019 |
| Art & Design of Shenfield Ltd | Wholesale & retail | 2014 |
| Art-Teh Ltd | Wholesale & retail | 2026 |
| Arthur JES Limited | Professional & scientific | 2015 |
| Artisan Decorating Ltd | Construction | 2025 |
| Arts Head Ltd | Other services | 2009 |
| AS Real Estate 1 Ltd | Real estate | 2026 |
| Ascc Limited | Professional & scientific | 2014 |
| Ascent Consulting Services Limited | Information & communication | 2016 |
| Ascots Group Ltd | Construction | 2019 |
| Aseda Holdco Limited | Financial services | 2026 |
| ASH Green Investments Ltd | Other services | 2023 |
| ASH Tree Interiors Limited | Construction | 2019 |
| Ashdal Property Solutions Ltd | Construction | 2023 |
| Asher Consulting Limited | Professional & scientific | 2023 |
| Ashfield Associates (UK) Ltd | Administrative & support | 2014 |
| Ashmeads (Loughton) Maintenance Limited | Households | 1966 |
| Ashmere Resident (2) Management Company Limited | Households | 2022 |
| Ashmere Resident Management Company Limited | Households | 2021 |
| Ashton Villas Broadstairs Limited | Households | 2026 |
| Ashvale Investment Group Ltd | Construction | 2024 |
| Ashwell Developments Limited | Construction | 2016 |
| Ashwells Court Management Company Ltd | Real estate | 2022 |
| Ashworth Analytics Ltd | Information & communication | 2015 |
| ASI Zinar Ltd | Wholesale & retail | 2026 |
| ASK and Task Limited | Information & communication | 2025 |
| Aslk Chan Development Ltd | Real estate | 2020 |
| Asmodee Entertainment Limited | Information & communication | 2019 |
| Aspect Carpenters Ltd | Construction | 2018 |
| Aspect Studios Limited | Professional & scientific | 2021 |
| Aspire Communication Services Limited | Administrative & support | 2017 |
| Aspire Rehab Limited | Health & social care | 2014 |
| Aspire Tennis Academy Ltd | Education | 2019 |
| Asprey Medical Services Ltd | Administrative & support | 2013 |
| ASQ Consultancy Services Limited | Professional & scientific | 2018 |
| Assert Ltd | Information & communication | 2006 |
| Asset Car Club Ltd | Wholesale & retail | 2012 |
| Asset Development and Management Ltd | Construction | 2013 |
| Assosia Ltd | Information & communication | 2003 |
| Assure Property Maintenance Ltd | Construction | 2023 |
| Assured Fire & Security Ltd | Administrative & support | 2022 |
| Aston Building & Conservation Ltd | Construction | 2017 |
| Aston FOX Ltd | Real estate | 2020 |
| Aston Rothbury PLC | Financial services | 1993 |
| Astraea Athletic Ltd | Wholesale & retail | 2023 |
| Astrum Investments Ltd | Real estate | 2021 |
| Astute Surveyors Ltd | Professional & scientific | 2021 |
| Asunny Construction Ltd | Construction | 2024 |
| Asymmetric Engineering Limited | Information & communication | 2019 |
| AT Construction Developments Ltd | Construction | 2017 |
| AT Home With... Limited | Education | 2018 |
| AT Last Events Limited | Manufacturing | 2018 |
| Atallon Homes Ltd | Construction | 2015 |
| Atec Academics Ltd | Education | 2019 |
| Atec Engineering Limited | Administrative & support | 1997 |
| ATG Support Ltd | Administrative & support | 2020 |
| Athans International Ltd | Wholesale & retail | 2026 |
| Atheena UK Ltd | Administrative & support | 2017 |
| Athena London Stationers Limited | Wholesale & retail | 2020 |
| Atik 3D Ltd | Manufacturing | 2025 |
| Atlanta Estates Ltd | Construction | 1998 |
| Atlantis Heating Solutions Limited | Construction | 2018 |