| Alpaca Pals Ltd | Extraterritorial | 2011 |
| Alpha Photographic Ltd | Professional & scientific | 2007 |
| Alphatale Ventures Ltd | Wholesale & retail | 2019 |
| Alston Ltd | Financial services | 2021 |
| Altogether Care (Holdings) Ltd | Financial services | 2024 |
| Altogether Care - Contract Management Ltd | Professional & scientific | 2021 |
| Alton Pancras Estate UK Ltd. | Agriculture & fishing | 2014 |
| Amadent Lettings Limited | Real estate | 2020 |
| Amadent Limited | Real estate | 2009 |
| Amailia Limited | Construction | 2004 |
| Amanda J Molyneux & Company Limited | Other services | 2008 |
| Amanda Janes Florist Limited | Extraterritorial | 2024 |
| Amanda Janes Flowers Limited | Wholesale & retail | 2024 |
| Amartob Limited | Health & social care | 2015 |
| Amazing Creative Ltd | Professional & scientific | 2011 |
| Ambrose Consulting Limited | Professional & scientific | 1993 |
| Ametrine Holistics Solutions Ltd | Health & social care | 2025 |
| AMH Data Limited | Information & communication | 2019 |
| Amnr Consulting Limited | Professional & scientific | 2014 |
| Amoeba Movement Limited | Wholesale & retail | 2026 |
| Amolite Consulting Ltd | Administrative & support | 2012 |
| Amrap Properties Ltd | Real estate | 2026 |
| Amro Care Ltd | Health & social care | 2026 |
| AMY Maddison Limited | Other services | 2004 |
| Anagram People Limited | Administrative & support | 2007 |
| ANB Service Solutions Ltd | Administrative & support | 2018 |
| Ancestra Limited | Extraterritorial | 2025 |
| Anchiano Limited | Professional & scientific | 2021 |
| Andrew Blaney Ltd. | Arts & recreation | 2004 |
| Andrew Stone Architect Limited | Professional & scientific | 2006 |
| Andrew Tory & Partners LLP | | 2018 |
| Andrew Tory Ltd | Agriculture & fishing | 2018 |
| Andy & ROB Services Limited | Construction | 2019 |
| Andy Crabb Ltd | Administrative & support | 2014 |
| Andy Harvey Limited | Wholesale & retail | 2015 |
| Andy Neill Farm Services Limited | Agriculture & fishing | 2008 |
| Andy Parsons & Associates Limited | Administrative & support | 2007 |
| Angel Clean 1972 Limited | Administrative & support | 2020 |
| Angel Exit Theatre Limited | Arts & recreation | 2008 |
| Angel Mews (Poole) Management Limited | Real estate | 2003 |
| Anglo Caledonian Limited | Extraterritorial | 1995 |
| Anglotown (1937) Ltd | Real estate | 2008 |
| Angrave Properties Limited | Other services | 2014 |
| Animal Rehab Partners Ltd | Professional & scientific | 2024 |
| ANN Lewis Health Ltd | Health & social care | 2021 |
| Anna West Limited | Health & social care | 2022 |
| Ansbury House (Poundbury) Management Company Limited | Households | 2015 |
| Anthony COX Limited | Administrative & support | 2011 |
| Anthony Holland Plumbing and Heating Limited | Construction | 2009 |
| Anthony Stratton Limited | Health & social care | 2017 |
| Apmm Garage Ltd | Wholesale & retail | 2025 |
| Applied Acoustic Intelligence Ltd | Professional & scientific | 2025 |
| Applied Emissions Ltd | Professional & scientific | 2017 |
| Aprajay Golash Limited | Health & social care | 2003 |
| Aprenzi Consultancy Limited | Professional & scientific | 2008 |
| APT Translations Ltd | Professional & scientific | 2007 |
| APT Transtelex Ltd | Professional & scientific | 1974 |
| Aqua Store Ltd. | Extraterritorial | 2020 |
| Aquaheat Services Limited | Construction | 2006 |
| Aquatech Drainage Consultants Ltd | Other services | 2003 |
| Aquavein Limited | Extraterritorial | 2020 |
| ARB Hunter Limited | Agriculture & fishing | 2025 |
| Arcade 31 Ltd | Wholesale & retail | 2024 |
| Arcade Flowers Limited | Wholesale & retail | 2010 |
| Archie’S Artisan Bakery Ltd | Wholesale & retail | 2020 |
| Arcis Risk Limited | Professional & scientific | 2026 |
| Arctic Refrigerated Trailers Limited | Administrative & support | 2020 |
| Arena 4 Finance Ltd. | Financial services | 2004 |
| Aria Isabella Limited | Real estate | 2020 |
| Arias Barbers Ltd | Other services | 2023 |
| Arinna Experience Ltd | Administrative & support | 2025 |
| Arla Tide Marine LLP | | 2023 |
| Armswell Property LLP | | 2025 |
| Arnold Jones Associates Design Limited | Professional & scientific | 2001 |
| Arnold Jones Associates Property Limited | Hospitality | 1997 |
| Arrowbase Portland Ltd | Households | 2020 |
| Art Community Theatre LDN CIC | Arts & recreation | 2024 |
| Art in Poundbury CIC | Arts & recreation | 2023 |
| Art Theatre London Ltd | Arts & recreation | 2021 |
| Arta GAP Limited | Health & social care | 2016 |
| Artemis Graphic Designs Limited | Professional & scientific | 2012 |
| Artisans' Bazaar Ltd | Wholesale & retail | 2019 |
| Artiscapes Grounds Maintenance Ltd | Administrative & support | 2025 |
| Artsreach | Arts & recreation | 1996 |
| Artura Construction Limited | Construction | 2022 |
| Artura Homes Limited | Construction | 2021 |
| Artwey Community Interest Company | Arts & recreation | 2009 |
| AS Technical Solutions Limited | Administrative & support | 2009 |
| Asap Drainage Limited | Water & waste | 2020 |
| Ascent Cars and Cabs Ltd | Transport & logistics | 2025 |
| Ascot Advisory Limited | Professional & scientific | 2024 |
| Ashley Barn Accountancy Limited | Professional & scientific | 2018 |
| Ashley Wood Holdings Ltd | Financial services | 2024 |
| Ashley Wood Recovery Limited | Wholesale & retail | 1999 |
| Ashley Wood Recovery South Ltd | Wholesale & retail | 2024 |
| Asil Developments Limited | Real estate | 2022 |
| Aspley Associates LLP | | 2004 |
| Assentium Limited | Information & communication | 2016 |
| Association for Cognitive Analytic Therapy | Health & social care | 2007 |
| Aston House Raynes Park Limited | Households | 2011 |