| Advanced Clinical Research Services Limited | Professional & scientific | 2018 |
| Advanced Control Solutions Limited | Administrative & support | 1991 |
| Advanced Crystal Technology Limited | Professional & scientific | 1985 |
| Advanced Molecular Vision Limited | Other services | 2006 |
| Advent Property (Guildford) Ltd | Real estate | 2024 |
| Adventgb Limited | Wholesale & retail | 2021 |
| Adventure Queens Ltd | Arts & recreation | 2021 |
| Advice Made Simple Limited | Financial services | 2006 |
| AE Electrical Services Limited | Construction | 2022 |
| AEC BIM Tools Ltd | Information & communication | 2021 |
| Aefifty Ltd | Administrative & support | 2005 |
| Aegon Private Ltd | Wholesale & retail | 2026 |
| Aeneid Limited | Administrative & support | 2016 |
| Aeon Medical Aesthetics Limited | Health & social care | 2013 |
| Aerial Express Ltd | Administrative & support | 2003 |
| Aerious Limited | Information & communication | 2010 |
| Aero-Gate Europe Ltd | Manufacturing | 2015 |
| Aeronextech Ltd | Information & communication | 2023 |
| Aethereality Company Limited | Wholesale & retail | 2023 |
| Aethernet Services Ltd | Administrative & support | 2017 |
| AFC Totton Prestige Ltd | Administrative & support | 2024 |
| Affinitas Limited | Professional & scientific | 2021 |
| Affinity Digital (Technology) Limited | Information & communication | 2004 |
| Afra Labs Ltd | Information & communication | 2025 |
| Africa Lopez Ruiz Ltd | Other services | 2024 |
| African Mountain Equipment Ltd | Professional & scientific | 2005 |
| Afrikdeli Ltd | Hospitality | 2018 |
| AG Learning Ltd | Education | 2020 |
| AGC Management Limited | Extraterritorial | 2016 |
| Agefame Limited Liability Partnership | | 2002 |
| Agent Blanc Limited | Wholesale & retail | 2022 |
| Agent-Support-Consultancy Limited | Professional & scientific | 2023 |
| Aggie Club C.I.C. | Hospitality | 2025 |
| Agile Business Analysis Limited | Administrative & support | 2015 |
| AGK Consulting Ltd | Professional & scientific | 2019 |
| Agoston Wines Limited | Extraterritorial | 2016 |
| AGR Dynamics Ltd | Administrative & support | 2006 |
| Agrivolt Ltd | Agriculture & fishing | 2025 |
| Agsales Ltd | Wholesale & retail | 2024 |
| AHA Partnerships Limited | Professional & scientific | 2022 |
| AHA2 Consulting Ltd | Information & communication | 2023 |
| Ahhone Holdings Ltd | Financial services | 2020 |
| Ahora Education Ltd | Education | 2021 |
| AI Technology Limited | Construction | 2014 |
| Ai-Med Ltd | Information & communication | 2024 |
| Aide Online Limited | Professional & scientific | 2016 |
| Aidsystems Ltd | Professional & scientific | 2024 |
| Aikon Communications Ltd | Extraterritorial | 2013 |
| Aileron Ltd | Professional & scientific | 2022 |
| AIM Consulting and Trade Ltd | Hospitality | 2024 |
| AIM Cortex Limited | Information & communication | 2026 |
| AIM Removals and Storage Limited | Transport & logistics | 2018 |
| AIM Technology Partnership Ltd | Information & communication | 2011 |
| Ainsworth Construction and Electrical Limited | Construction | 2016 |
| Aion Bidco Limited | Financial services | 2022 |
| Aion Holdco Limited | Financial services | 2022 |
| Aion Midco Limited | Financial services | 2022 |
| Aion Topco Limited | Financial services | 2022 |
| Air Copier Systems Ltd | Administrative & support | 2003 |
| Air Hub Property Ltd | Real estate | 2019 |
| Air Social Ltd. | Professional & scientific | 2010 |
| Air Social Property Ltd | Professional & scientific | 2021 |
| Airhealth Junction Ltd | Wholesale & retail | 2023 |
| Airtight Accountancy Ltd | Professional & scientific | 2017 |
| Aitekin Ltd | Information & communication | 2013 |
| Aitken Associates Ltd | Real estate | 2010 |
| Aivyla Cole Ltd | Professional & scientific | 2022 |
| Ajako Amolese Multi Limited | Health & social care | 2025 |
| AJD Vehicle Maintenance and Repair Limited | Wholesale & retail | 2024 |
| AJH Accounting Services Limited | Professional & scientific | 1998 |
| Ajncy Limited | Information & communication | 2025 |
| AJP Consulting Solutions Ltd | Information & communication | 2025 |
| AJW Energy Limited | Energy | 2013 |
| Akal Rescue Training Group Ltd | Education | 2026 |
| AKC Roofing Ltd | Construction | 2017 |
| Akdt Limited | Professional & scientific | 2014 |
| AKP IT Limited | Information & communication | 2009 |
| AKP Projects Ltd | Real estate | 2014 |
| AKS Radiology Limited | Health & social care | 2019 |
| Alan James Limited | Financial services | 1961 |
| Alan Sharp Associates Limited | Professional & scientific | 2011 |
| Alazid Limited | Professional & scientific | 2025 |
| Albatross Film Holdings Ltd | Information & communication | 2020 |
| Albemarle Property Company Limited | Real estate | 1934 |
| Alberta Properties Limited | Real estate | 1996 |
| Albury Alternative Investments Limited | Financial services | 2022 |
| Albury Canongate Holdco Limited | Real estate | 2020 |
| Albury Canongate Limited | Real estate | 2020 |
| Albury Capital Partners Limited | Real estate | 2019 |
| Albury Care Home Limited | Health & social care | 2009 |
| Albury Care Limited | Health & social care | 1996 |
| Albury Energy Ltd | Professional & scientific | 2025 |
| Albury Heights Residents Company Limited | Households | 1986 |
| Albury Holdings Limited | Construction | 2020 |
| Albury Sports Club Limited | Arts & recreation | 2013 |
| Albury Vineyard Holdings Limited | Financial services | 2020 |
| Albury Vineyard Limited | Agriculture & fishing | 2006 |
| Albury Vineyard Management Ltd | Professional & scientific | 2018 |
| Alchemed Limited | Information & communication | 2022 |
| Alcis Holdings Limited | Public administration | 2004 |