| Agritierra Limited | Information & communication | 2021 |
| AGT Ceilings and Partitions Limited | Construction | 2019 |
| AI Infra Consulting Limited | Administrative & support | 2025 |
| AI Tools 4 Agents Ltd | Information & communication | 2025 |
| AID Aviation Limited | Transport & logistics | 2010 |
| Aidacare Limited | Health & social care | 2021 |
| Aimberry Homes Limited | Real estate | 2016 |
| Aimero Design Agency Ltd | Professional & scientific | 2024 |
| Aina Initiative Ltd | Education | 2024 |
| Airblu Limited | Construction | 2010 |
| Airconic Air Conditioning Ltd | Construction | 2025 |
| Aird Biotechnology Services Limited | Professional & scientific | 2010 |
| Airlocker Ltd | Information & communication | 2024 |
| AIS Assistant Ltd | Professional & scientific | 2026 |
| AJ Active Solutions Limited | Information & communication | 1997 |
| AJ Environmental Recovery Services Limited | Construction | 2010 |
| AJ Party Gifts Ltd | Wholesale & retail | 2023 |
| AJE Wealth Management Limited | Financial services | 2023 |
| Ajit Ltd | Health & social care | 2010 |
| Ajswan Engineering Ltd | Manufacturing | 2025 |
| Ajva Ltd | Administrative & support | 2022 |
| AK Smiles Ltd | Health & social care | 2022 |
| AKS & JSS Limited | Hospitality | 2017 |
| AL Simpson Music Limited | Arts & recreation | 2022 |
| Alan Alger Ltd | Professional & scientific | 2023 |
| Albany Leadership Ltd | Extraterritorial | 2026 |
| Albaware Ltd | Information & communication | 2011 |
| ALD Properties Limited | Real estate | 2006 |
| Alderaan-Labs Limited | Professional & scientific | 2026 |
| Aldwych Securities Limited | Real estate | 1999 |
| Alentar Care Limited | Health & social care | 2022 |
| Alentar Group Limited | Health & social care | 2022 |
| Aleva Labs Limited | Manufacturing | 2024 |
| Alexander Advisory Group Limited | Education | 2025 |
| Alexander Consulting (UK) Ltd | Professional & scientific | 2014 |
| Alexander J Brett Ltd | Administrative & support | 2025 |
| Alexander Ross Bespoke Ltd | Manufacturing | 2025 |
| Alexandra ARC Ltd | Wholesale & retail | 1975 |
| Alexandra Court (ST Ives) Management Limited | Households | 1989 |
| Alexandra Place (Hemel Hempstead) Management Company Limited | Households | 2015 |
| Alexandre Developments Limited | Construction | 1998 |
| Alfa Autos Ltd | Wholesale & retail | 2019 |
| Alfie Bates Coaching Ltd | Professional & scientific | 2019 |
| Alfieroy Limited | Professional & scientific | 2023 |
| Alfredton Company Limited | Extraterritorial | 2012 |
| Alife Construction Limited | Construction | 2025 |
| Alife Estates Limited | Real estate | 2014 |
| Alisha Stephenson Piling Limited | Construction | 2025 |
| Alison Weston Limited | Other services | 2011 |
| Alistair Elliott Ltd | Professional & scientific | 2012 |
| ALL About Events Management Limited | Professional & scientific | 2017 |
| ALL About Rentals Ltd | Real estate | 2022 |
| ALL Channels Ltd | Information & communication | 2023 |
| ALL Goods Hub Ltd | Wholesale & retail | 2024 |
| ALL Jointing Solutions Ltd | Construction | 2023 |
| ALL Sole'D OUT Ltd | Wholesale & retail | 2022 |
| ALL Things Sweet Ltd | Wholesale & retail | 2019 |
| ALL Things Trading Limited | Wholesale & retail | 2019 |
| Allan Smith Accounting & Tax Limited | Professional & scientific | 2001 |
| Allen Mezzanines Limited | Construction | 2021 |
| Allied Brickwork Ltd. | Construction | 2011 |
| Allina Limited | Other services | 2016 |
| Alliora Consulting Limited | Professional & scientific | 2025 |
| Allplastics Holdings Ltd | Financial services | 2021 |
| Allplastics Limited | Wholesale & retail | 1982 |
| Allsebrook Pumps Limited | Construction | 1997 |
| Almar Properties (Southgate) Limited | Real estate | 1962 |
| Almar Two Ltd | Financial services | 2016 |
| Almo Creative Productions Limited | Professional & scientific | 2019 |
| Alopartners Consulting Ltd | Professional & scientific | 2025 |
| Alordon Ltd | Other services | 2023 |
| Alscot Investments Limited | Real estate | 1960 |
| Alta Hairdressing Limited | Other services | 2025 |
| Altham Limited | Wholesale & retail | 2003 |
| Altitude Drone Surveying Ltd | Information & communication | 2023 |
| Altitude Ventures Ltd | Arts & recreation | 2026 |
| Alty Limited | Other services | 2022 |
| Alvarez Holdings Limited | Financial services | 2020 |
| Alyssa Smith Jewellery Limited | Manufacturing | 2012 |
| Alyth Property Acquisitions Limited | Real estate | 2023 |
| AMA Facilities Limited | Administrative & support | 2024 |
| Amadora Asset Management Limited | Construction | 2010 |
| Amanda Ransom Design Limited | Administrative & support | 2011 |
| Amani Kitchen Ltd | Hospitality | 2024 |
| Amar Precision Machine Tools Limited | Manufacturing | 2026 |
| Amare Holdings Ltd | Financial services | 2022 |
| Amato Construction Ltd | Construction | 2021 |
| Amato Developments Ltd | Real estate | 2024 |
| Amazing Apprenticeships Limited | Professional & scientific | 2015 |
| Amazing Occasions Limited | Other services | 2018 |
| AMAZING3D Limited | Manufacturing | 2021 |
| Ambertec Opportunities Ltd | Education | 2013 |
| Ambiance & Solace Therapies Ltd | Health & social care | 2010 |
| Ambison Management Limited | Construction | 2015 |
| Ambrose Developments Limited | Real estate | 1972 |
| Amia Boutique Ltd | Wholesale & retail | 2024 |
| Amicus Services Limited | Construction | 2007 |
| Ammas Limited | Manufacturing | 1983 |
| Amor Property Ventures Limited | Real estate | 2022 |
| Amore Restaurant St.Ives Limited | Real estate | 2022 |