| AMS 1615 Limited | Professional & scientific | 2003 |
| Amtrak Sameday Limited | Transport & logistics | 2008 |
| Amuse Construction Limited | Construction | 2025 |
| AMW Performance Ltd | Wholesale & retail | 2023 |
| AMY Jayne Aesthetics Limited | Other services | 2017 |
| AMY Louise Burford Ltd | Extraterritorial | 2023 |
| Amygo Ltd | Wholesale & retail | 2023 |
| An-Tony-Transport Ltd | Transport & logistics | 2024 |
| ANA Mrso Limited | Health & social care | 2022 |
| Anaya Superstore Limited | Wholesale & retail | 2025 |
| Anchor Document Storage Limited | Administrative & support | 2004 |
| Anctech Limited | Information & communication | 2026 |
| Anda Hydraulics Co., Ltd | Manufacturing | 2023 |
| Andaleeb Breast Care Services Ltd | Health & social care | 2023 |
| Anddip Ltd | Real estate | 2020 |
| Anderson M Care Services Ltd | Administrative & support | 2025 |
| Anderson M Services Ltd | Transport & logistics | 2014 |
| Andikas Global Ltd | Wholesale & retail | 2025 |
| Andrealicious Carpasserie Ltd | Hospitality | 2024 |
| Andrei Building Construction UK Ltd | Construction | 2026 |
| Andrew Wells Architectural Planning & Design Ltd | Professional & scientific | 2012 |
| ANE Campers Ltd | Wholesale & retail | 2020 |
| Aneeas Limited | Information & communication | 2022 |
| Angel Court (Shaftesbury) Management Company Limited | Households | 2019 |
| Angel Saunari Limited | Wholesale & retail | 2018 |
| Animals Lost and Found in Kent | Professional & scientific | 2016 |
| Aninamart Limited | Wholesale & retail | 2025 |
| Anitam Limited | Real estate | 2023 |
| Anitein.Com Limited | Wholesale & retail | 2017 |
| Annesei Ltd | Health & social care | 2018 |
| Annihilate Ltd | Transport & logistics | 2018 |
| Another Planet Music Limited | Information & communication | 2013 |
| Anping County Joylink Wire Mesh Co., Ltd. | Professional & scientific | 2018 |
| Anping County Yexiang Hardware Wiremesh Products Limited | Manufacturing | 2019 |
| Anpingxian Xinhongyuan Wire Mesh Products Co., Limited | Professional & scientific | 2018 |
| Anto Link Nutrition Co., Ltd | Extraterritorial | 2017 |
| ANY Storage Ltd | Transport & logistics | 2019 |
| Anybody Beauticians Ltd | Other services | 2022 |
| Anysam Ltd | Construction | 2016 |
| Anystore Ltd | Extraterritorial | 2019 |
| Anytime ANY Day Ltd | Construction | 2026 |
| AO Property Services Ltd | Real estate | 2021 |
| Aohai Heavy Industry International Co., Ltd. | Wholesale & retail | 2024 |
| AP Engineering and Fabrication Ltd | Manufacturing | 2019 |
| AP Group Contracting UK Ltd | Construction | 2018 |
| APC Holidays Ltd | Hospitality | 2019 |
| Apex Emergency Solutions Ltd | Wholesale & retail | 2025 |
| Apex K9 Ltd | Agriculture & fishing | 2024 |
| Aplinfu Ltd | Real estate | 2015 |
| Apo’S Investments Limited | Hospitality | 2025 |
| Apple Meadow Developments Ltd | Construction | 2022 |
| Application Security Ltd | Administrative & support | 2016 |
| Approved Spotless Cleaning Services Limited | Extraterritorial | 2005 |
| APS Property Holdings (Kent) Ltd | Real estate | 2025 |
| Aquabars Inn Ltd | Wholesale & retail | 2019 |
| Aquamorphic Limited | Professional & scientific | 2008 |
| Aquaspec Solutions Limited | Extraterritorial | 2025 |
| Aquatherm U.K. Limited | Manufacturing | 2018 |
| AR & HKA Limited | Real estate | 2025 |
| AR Construction & Builders Ltd | Construction | 2025 |
| ARA Development Limited | Construction | 2025 |
| Arbility App Ltd | Information & communication | 2023 |
| Arbility Ltd | Agriculture & fishing | 2019 |
| Arbuckle and Sons Ltd | Real estate | 2019 |
| ARC Monitoring Limited | Administrative & support | 1999 |
| Arcbright Ltd | Other services | 2023 |
| Architechnology.Design Limited | Professional & scientific | 2019 |
| ARCHITECTURE24 Ltd | Professional & scientific | 2007 |
| Arclkg Ltd | Professional & scientific | 2026 |
| Areem Limited | Professional & scientific | 2012 |
| Arena Plant Ltd | Administrative & support | 2017 |
| ARG Joinery Limited | Construction | 2013 |
| Arian JJ Ltd | Wholesale & retail | 2017 |
| Ariel Health Services Ltd | Health & social care | 2023 |
| Arisaig Hotel Limited | Hospitality | 2013 |
| ARK Media Group Ltd | Information & communication | 2018 |
| ARK of GOD Parish Homes Ltd | Real estate | 2022 |
| Arkivon Group Ltd | Construction | 2026 |
| Arlosoft Ltd | Information & communication | 2011 |
| Armani Grill Ltd | Hospitality | 2024 |
| Armishaws Asset Management LLP | | 2023 |
| Armishaws Group Limited | Financial services | 2020 |
| Armishaws Holdings Limited | Extraterritorial | 2014 |
| Armishaws Media Limited | Financial services | 2022 |
| Armishaws Removals & Storage LLP | | 2024 |
| Armishaws Removals Ltd | Transport & logistics | 1998 |
| Armour Publishing Limited | Information & communication | 2010 |
| Armur Professional Services Limited | Construction | 2016 |
| Aroy Properties Limited | Real estate | 2026 |
| ARP Construct Ltd | Construction | 2025 |
| Arslan Khan Ltd | Wholesale & retail | 2026 |
| Art of Floors Ltd | Construction | 2024 |
| Art VIP Barber Gillingham Ltd | Other services | 2025 |
| Art VIP Barber Ltd | Other services | 2025 |
| Artelligent Ltd | Information & communication | 2019 |
| Article 8 & Sons Ltd | Wholesale & retail | 2020 |
| Artificial Stone Company Limited | Manufacturing | 1992 |
| Artius Interiors + Ltd | Construction | 2026 |
| Arushaan Holdings Limited | Real estate | 2024 |
| AS Automobile Ltd | Transport & logistics | 2018 |