| Alakirik Barbers Ltd | Other services | 2025 |
| Alana Marmion-Warr Limited | Information & communication | 2015 |
| Albert LC Limited | Transport & logistics | 2023 |
| Aldeburgh House (Freehold) Co Ltd | Households | 2022 |
| Aldersbrook Stables Community CIC | Education | 2023 |
| Alex OTT Architecture Ltd | Professional & scientific | 2022 |
| Alexanders Accountants Limited | Professional & scientific | 2022 |
| Alexanders Strategic Planning Limited | Professional & scientific | 2001 |
| ALI 786 Services Ltd | Health & social care | 2021 |
| Alive Natural Hair Ltd | Other services | 2023 |
| ALL Build Roofing Ltd | Construction | 2014 |
| ALL Elements Electrical Ltd | Construction | 2024 |
| ALL in Finance Ltd | Financial services | 2026 |
| ALL Tomorrow Limited | Administrative & support | 2025 |
| All's Fair Ltd | Wholesale & retail | 2022 |
| Allgreen Limited | Extraterritorial | 2001 |
| Alliance for Better Care CIC | Health & social care | 2014 |
| Allondeck.Co.Uk Ltd | Administrative & support | 2014 |
| Aloto Fleet Management Limited | Administrative & support | 2012 |
| Aloto Limited | Professional & scientific | 2012 |
| Aloto Logistics Limited | Transport & logistics | 2015 |
| Alouette Flying Club Limited | Other services | 1973 |
| Alpha Therapeutic Care Ltd | Health & social care | 2024 |
| ALT Roofline Services Limited | Construction | 2026 |
| ALT Software Limited | Information & communication | 2021 |
| Alternative Airlines Limited | Administrative & support | 1994 |
| Alternative Pest Control Ltd | Agriculture & fishing | 2014 |
| Amazora Ltd | Wholesale & retail | 2025 |
| Ambell Overseas Health for Africa Ltd | Extraterritorial | 2013 |
| Amberly Services Ltd | Professional & scientific | 2018 |
| Ameritex Limited | Real estate | 1987 |
| Amira P Rentals Ltd | Extraterritorial | 2024 |
| AML Claening Ltd | Administrative & support | 2018 |
| AMP International Ltd | Professional & scientific | 2009 |
| AMR Signs Ltd. | Manufacturing | 2013 |
| AMU Associates Ltd | Education | 2025 |
| Anadhya Corporation Ltd | Wholesale & retail | 2025 |
| Analysed Insights Ltd | Information & communication | 2024 |
| Andrea Strudwick Limited | Professional & scientific | 2016 |
| Andrew Peters Facilities Management Ltd | Construction | 2018 |
| Andrew Peters Holdings Limited | Construction | 2026 |
| Andrew Peters Limited | Manufacturing | 2012 |
| Anga Sales Ltd | Wholesale & retail | 2021 |
| Angelus Hair Supplies Limited | Administrative & support | 2013 |
| Anoziva Ltd | Information & communication | 2025 |
| Anthony Willett Limited | Professional & scientific | 2002 |
| Anusun Limited | Hospitality | 2026 |
| Aosta Ltd | Wholesale & retail | 2021 |
| Apex Build and Design Ltd | Construction | 2020 |
| Apex Financial Planning Ltd | Professional & scientific | 2024 |
| Apex Licensing Limited | Professional & scientific | 2022 |
| Apex Solutions (South East) Ltd | Construction | 2026 |
| APN Plumbing and Heating Ltd | Construction | 2022 |
| Apps Grab Hire Limited | Water & waste | 2021 |
| Aquashield Roofing Solutions Ltd | Construction | 2025 |
| ARA Automotive Ltd | Wholesale & retail | 2021 |
| Arcadia Financial Services Ltd | Financial services | 2016 |
| Arcane Roots LLP | | 2026 |
| Archard Talent Limited | Administrative & support | 2024 |
| Archibald & Sons Ltd | Wholesale & retail | 2025 |
| Archway Theatre Company Limited | Arts & recreation | 1956 |
| Arden Scaffolding Ltd | Construction | 2024 |
| Arditi Wargames Ltd | Manufacturing | 2026 |
| Arete Commerce Consulting Ltd | Information & communication | 2024 |
| Ariel Packaging Ltd | Manufacturing | 2011 |
| Aritma Barber Ltd | Other services | 2025 |
| ARK Lead Property Ltd | Real estate | 2024 |
| Arkadehair Ltd | Education | 2025 |
| Armada Electrical Ltd | Other services | 2023 |
| ARO Ventures Limited | Professional & scientific | 2025 |
| Arpan Productions Limited | Information & communication | 2024 |
| Arrow Constructions 2014 Limited | Construction | 2014 |
| Arrow Imports UK Ltd | Real estate | 2002 |
| Arrow Supreme Limited | Wholesale & retail | 2003 |
| Art Food & Wine Ltd | Wholesale & retail | 2022 |
| Art of Reinvention Limited | Extraterritorial | 2006 |
| Artemis Equine Vets Ltd | Professional & scientific | 2025 |
| Arundel Interiors Limited | Construction | 2018 |
| AS Green Solutions Limited | Construction | 2024 |
| ASA Buildings Ltd | Construction | 2026 |
| Ascendit Lifts Limited | Construction | 1998 |
| ASE Installations Ltd | Construction | 2020 |
| ASG Sports Ltd | Education | 2006 |
| Asgrek Ltd | Hospitality | 2020 |
| Ashcroft Care Services Limited | Health & social care | 2019 |
| Ashenhurst Holdings Ltd | Financial services | 2026 |
| Ashenhurst Properties Ltd | Real estate | 2026 |
| Asher Adeniyi Limited | Professional & scientific | 2015 |
| Ashurst Equestrian and Pet Ltd | Wholesale & retail | 2024 |
| Ashurst Farm Feeds Limited | Wholesale & retail | 2013 |
| Aslh SPV Ltd | Real estate | 2024 |
| Aspireuk Ltd | Transport & logistics | 2026 |
| Associated Painting Services Ltd | Construction | 2022 |
| Athinketh Ltd | Information & communication | 2022 |
| Atlas Flow Consultancy Ltd | Professional & scientific | 2026 |
| Attained London Ltd | Professional & scientific | 2023 |
| Atum Healthcare Limited | Extraterritorial | 2023 |
| Aurora Beauty Studios Limited | Other services | 2021 |
| Auto Body FIX Limited | Wholesale & retail | 2019 |
| Automatic Heating UK Ltd | Wholesale & retail | 2025 |