| Anga Corp Limited | Wholesale & retail | 2017 |
| Anghel's Limited | Transport & logistics | 2014 |
| Anglo European Trading (UK) Limited | Wholesale & retail | 2002 |
| Anglo European Trading Limited | Administrative & support | 2011 |
| Anglo Franco Ltd | Transport & logistics | 2025 |
| Anglo Indian Trading Limited | Wholesale & retail | 2011 |
| Angry Sauces Ltd | Manufacturing | 2023 |
| Animal Physiotherapy Limited | Professional & scientific | 2009 |
| Anixter(U.K.)Limited | Other services | 1971 |
| Anjalikishore Infotech Limited | Information & communication | 2011 |
| Anna Lloyd Ltd | Professional & scientific | 2012 |
| Anna Luker.Com Ltd | Health & social care | 2019 |
| Annatoli Ltd | Professional & scientific | 2016 |
| Annesley Leisure Limited | Hospitality | 1994 |
| Annieleighcollection UK Ltd | Wholesale & retail | 2021 |
| Anning Associates Limited | Financial services | 2023 |
| Anoikis Solutions Ltd | Information & communication | 2026 |
| Ansley Brown Interiors Limited | Wholesale & retail | 2020 |
| Antham Electrical Ltd. | Construction | 1997 |
| Anthony Juer Lighting Limited | Manufacturing | 1948 |
| Antoniuc Capital Ltd | Construction | 2019 |
| Antoniuc Venture Ltd | Real estate | 2022 |
| Anubys Limited | Wholesale & retail | 2023 |
| Anything Electrical (CJ) Ltd | Energy | 2015 |
| Anything Left-Handed Limited | Wholesale & retail | 1968 |
| ANZ Plumbing and Heating Limited | Construction | 2012 |
| AP Home Renovation Ltd | Construction | 2023 |
| AP Investments Berkshire Limited | Real estate | 2023 |
| AP Pest Management Ltd | Administrative & support | 2025 |
| AP27 Cyber Solutions Limited | Information & communication | 2024 |
| Apart Studio Ltd | Arts & recreation | 2023 |
| APC & Associates Ltd | Real estate | 2014 |
| Apex Models Ltd | Other services | 2021 |
| Apex Skin Clinic Limited | Health & social care | 2025 |
| Apex Well Interventions Ltd | Other services | 2026 |
| APG Mechanical Services Ltd | Manufacturing | 2020 |
| Apple PIE Networks Ltd | Construction | 2023 |
| Appletree Spraying Ltd | Professional & scientific | 2024 |
| Applewood Kitchens LLP | | 2008 |
| Applied Card Technologies Limited | Professional & scientific | 2002 |
| Applied IT Solutions & Consultancy Services Ltd | Information & communication | 2023 |
| APPLY2EDUCATION Limited | Professional & scientific | 2016 |
| Appmilk Limited | Professional & scientific | 2012 |
| Appmilk Real Estate Limited | Real estate | 2021 |
| Apprendo Ltd | Information & communication | 2014 |
| Apricot Properties Limited | Real estate | 1999 |
| APS Coaching Ltd | Education | 2025 |
| Apsamuelson Solutions Ltd | Information & communication | 2013 |
| Aptine Care Services Ltd. | Health & social care | 2013 |
| Aptine International Investments Limited | Wholesale & retail | 2025 |
| AQ Care 2020 Limited | Health & social care | 2020 |
| Aqua Equine Ltd | Agriculture & fishing | 2025 |
| Aqua Impress Ltd | Construction | 2025 |
| Aquaglaze Ltd | Administrative & support | 2018 |
| Aquarius Financial Planning Ltd | Professional & scientific | 2020 |
| Aquasmart Plumbing and Heating Ltd | Construction | 2025 |
| Aquatech Consulting Ltd | Information & communication | 2007 |
| Aquen Ltd | Professional & scientific | 2026 |
| Aradash Ltd | Wholesale & retail | 2021 |
| Aradhya Ventures Limited | Information & communication | 2024 |
| Arale Ltd | Professional & scientific | 2015 |
| Arash Aryas Limited | Other services | 2019 |
| Arawa Cavendish Road Management Limited | Real estate | 2020 |
| Arbor Networks UK Limited | Wholesale & retail | 2004 |
| Arch Domestic Services Limited | Administrative & support | 2014 |
| Archer Interpreting Limited | Professional & scientific | 2021 |
| Arctic Flame Limited | Energy | 2024 |
| Ardeleana Romanian Traditional Store Ltd | Wholesale & retail | 2019 |
| Area Two Limited | Information & communication | 2015 |
| Arejayell Limited | Professional & scientific | 2019 |
| Arete Energy Limited | Mining & quarrying | 2025 |
| ARF Roofing Ltd | Construction | 2021 |
| Argraves Limited | Administrative & support | 2002 |
| Arietta Medtech Consulting Limited | Professional & scientific | 2018 |
| Arietta Musical Concepts Limited | Manufacturing | 2020 |
| Aris Software UK Ltd | Information & communication | 2024 |
| Ariska Limited | Transport & logistics | 2014 |
| Aristera Holdings Limited | Financial services | 2018 |
| Ariya Neuro Care (Residential) Limited | Health & social care | 2020 |
| Ariya Neuro Care (Supported Living) Limited | Health & social care | 2016 |
| Arkk Projects Limited | Construction | 2023 |
| Arkle Electrical Limited | Construction | 2015 |
| Armstrong Heating and Plumbing Services Ltd | Construction | 2008 |
| Arogy Beauty and Holistic Therapies Ltd | Other services | 2025 |
| Arrecco Ltd | Construction | 2019 |
| Art Constraction Limited | Construction | 2024 |
| Art Craft Limited | Manufacturing | 2017 |
| Artadrive Ltd | Wholesale & retail | 2025 |
| Artemis Adventure Ltd | Arts & recreation | 2011 |
| Arthur Management Limited | Households | 2017 |
| Artivia Limited | Real estate | 2026 |
| Arya Motors Ltd | Wholesale & retail | 2024 |
| Arya Spark Digital Ltd | Professional & scientific | 2025 |
| AS Decor & Painting Ltd | Construction | 2026 |
| AS Gates Limited | Construction | 2017 |
| AS Point A2B Logistic Ltd | Transport & logistics | 2023 |
| Ascend AI Ltd | Information & communication | 2024 |
| Ascendant Aviation Limited | Information & communication | 2005 |
| Ascendant Financial Limited | Professional & scientific | 2000 |
| Ascendant Group Limited | Professional & scientific | 2005 |