| Anzen Properties Ltd | Construction | 2012 |
| Anzen Secure Ltd | Information & communication | 2025 |
| Anzen South West Limited | Administrative & support | 2015 |
| AOE Alpha Omega Europa Ltd | Information & communication | 2025 |
| AOG Freight Limited | Extraterritorial | 2011 |
| Aouni Agence Ltd | Wholesale & retail | 2021 |
| Ap&P Services Ltd | Wholesale & retail | 2018 |
| Aparo Ltd | Professional & scientific | 2017 |
| Apartment 134 Limited | Arts & recreation | 2016 |
| Apeps Supplies Ltd | Wholesale & retail | 2026 |
| Apex Advertising Group Ltd | Professional & scientific | 2023 |
| Apex Aviation Flight Services Limited | Transport & logistics | 2022 |
| Apex CB Financial Planning Limited | Financial services | 2004 |
| Apex Knowledge Co Limited | Information & communication | 2026 |
| Apex Land Management Ltd | Professional & scientific | 2026 |
| Apex Service Centre Ltd | Wholesale & retail | 2025 |
| Apexway Connect Limited | Transport & logistics | 2025 |
| Apexx Roofing Repairs Limited | Construction | 2025 |
| Apis Natural Cosmetics Ltd | Wholesale & retail | 2021 |
| Aplin Carpentry Ltd | Construction | 2021 |
| APM Motors Ltd | Wholesale & retail | 2023 |
| Apollo Systems Contracts Limited | Administrative & support | 1996 |
| App Engine Ltd | Information & communication | 2025 |
| Apparato Ltd | Manufacturing | 2025 |
| Apparel MAN Limited | Manufacturing | 2012 |
| Apple Cinnamon Limited | Financial services | 2025 |
| Apple Landscapes Limited | Administrative & support | 2026 |
| Applecourt Limited | Construction | 1994 |
| Appletree Development (Homes) Limited | Administrative & support | 2016 |
| Appliances Plus Ltd. | Wholesale & retail | 2015 |
| Applied PM Consultancy Ltd | Professional & scientific | 2022 |
| Applied Relay Testing Ltd. | Manufacturing | 1992 |
| Applied Workplace Ltd | Construction | 2009 |
| Appoint Consultants Limited | Administrative & support | 2000 |
| Apprad Ltd | Administrative & support | 2019 |
| Apprentice Living Group Ltd | Real estate | 2025 |
| Approve Cleaning Limited | Administrative & support | 2016 |
| Appsflyer UK Ltd | Professional & scientific | 2016 |
| Apptician Limited | Extraterritorial | 2022 |
| Apricode International Ltd | Information & communication | 2025 |
| APS Grinding Ltd | Professional & scientific | 2023 |
| APS Professional Services Ltd | Professional & scientific | 2017 |
| Apsc Ltd | Professional & scientific | 2022 |
| Apsley House Care Home Limited | Health & social care | 2019 |
| Aptiflow Limited | Professional & scientific | 1998 |
| Aptiva Limited | Construction | 1992 |
| Aptiva Thermal Limited | Construction | 2020 |
| Aqana Ltd | Hospitality | 2025 |
| Aqua (Poole) RTM Company Limited | Households | 2026 |
| Aqua 18 Dorchester LLP | | 2008 |
| Aqua Ampress Park LLP | | 2023 |
| Aqua Angel Court LLP | | 2021 |
| Aqua Blandford LLP | | 2021 |
| Aqua Citygate LLP | | 2011 |
| Aqua Cross Keys LLP | | 2021 |
| Aqua Data Ltd | Professional & scientific | 1988 |
| Aqua Deep Blue LLP | | 2021 |
| Aqua Electra LLP | | 2009 |
| Aqua Hamworthy LLP | | 2021 |
| Aqua Heating (Poole) Limited | Construction | 2017 |
| Aqua House 22 LLP | | 2015 |
| Aqua House 2A LLP | | 2015 |
| Aqua Lansdowne LLP | | 2009 |
| Aqua Meeson LLP | | 2010 |
| Aqua Mercury Partnership LLP | | 2008 |
| Aqua Modular Ltd | Other services | 2023 |
| Aqua Northbourne LLP | | 2018 |
| Aqua Nova LLP | | 2010 |
| Aqua Paignton LLP | | 2021 |
| Aqua Seabourne 34 LLP | | 2013 |
| Aqua South Partnership LLP | | 2006 |
| Aqua Southbourne Grove LLP | | 2021 |
| Aqua Surf Limited | Wholesale & retail | 2024 |
| Aqua Tamarisk LLP | | 2009 |
| Aqua Tilehurst LLP | | 2021 |
| Aqua Walhampton 57A LLP | | 2016 |
| Aqua Wimborne LLP | | 2021 |
| Aqua Wotton LLP | | 2021 |
| Aqua Wyke Residential LLP | | 2021 |
| Aqualights POM and Twirl Troupe Ltd | Arts & recreation | 2019 |
| Aquamail Limited | Other services | 1992 |
| Aquarian Pools (Retail) Limited | Wholesale & retail | 2005 |
| Aquarius Managed Properties Limited | Real estate | 2001 |
| Aquarius Marine Coatings Limited | Wholesale & retail | 1996 |
| Aquatic Jetpacks Limited | Arts & recreation | 2013 |
| Aquinas Tuition Limited | Education | 2025 |
| Aquinous Group Ltd | Wholesale & retail | 2025 |
| AQW Limited | Information & communication | 2017 |
| AR & RR Education Ltd | Information & communication | 2015 |
| AR Competitions Ltd | Information & communication | 2026 |
| ARA Digital Ltd | Real estate | 2021 |
| Arabia Court Management (Hythe) Limited | Households | 1998 |
| Arafat Abir Ltd | Wholesale & retail | 2025 |
| Arapay Limited | Wholesale & retail | 2025 |
| Araujo Solutions Limited | Wholesale & retail | 2025 |
| Arbishops Limited | Wholesale & retail | 2021 |
| Arbiter Elegantiae Limited | Professional & scientific | 2018 |
| Arbitrage FBA (UK) Limited | Extraterritorial | 2021 |
| Arbor Vitae Garden Care Ltd | Arts & recreation | 2020 |
| Arborvitae Tree Care Ltd | Agriculture & fishing | 2008 |