| Aitchison Insights Ltd | Information & communication | 2026 |
| AJ Perrin Associates Limited | Extraterritorial | 2013 |
| AJ Samuel Ltd | Real estate | 2021 |
| Aj&Me Limited | Information & communication | 2017 |
| Aj's Food and Drink Ltd | Wholesale & retail | 2017 |
| AJC Accounting Services Ltd | Professional & scientific | 2019 |
| AJS Audits Ltd | Professional & scientific | 2024 |
| AJS Events Limited | Information & communication | 2010 |
| Akebia Business Services Ltd | Professional & scientific | 2023 |
| Akmedicons Limited | Health & social care | 2020 |
| Akoama Limited | Wholesale & retail | 2010 |
| Akonu Health Ltd | Health & social care | 2021 |
| AKP2045 Property Holdings Ltd | Real estate | 2019 |
| Akshaya Finance Ltd | Administrative & support | 2017 |
| Alameda Bookings Ltd | Administrative & support | 2017 |
| Alan Bettin (Swimming Pools) Limited | Construction | 1988 |
| Alasdair Marks Sustainability Consulting Ltd | Professional & scientific | 2021 |
| Alastair Dickenson Limited | Wholesale & retail | 2002 |
| Alberta Close Residents Management Company Limited | Households | 2016 |
| Albury Court Management Company Limited | Households | 1983 |
| Albury Tech Limited | Administrative & support | 2020 |
| Alcheme Advisors Limited | Professional & scientific | 2012 |
| Alchemed Bioscience Consulting Ltd | Professional & scientific | 2020 |
| Alde Care Ltd | Health & social care | 2012 |
| Aldershot Contemporary CIC | Arts & recreation | 2025 |
| Aldershot Rooms Ltd | Households | 2026 |
| Aleron Group Limited | Professional & scientific | 2009 |
| Aleron Partners Limited | Professional & scientific | 2011 |
| Alex Scrimgeour Investments Ltd | Real estate | 2017 |
| Alexander Groom Fine Art Ltd | Arts & recreation | 2023 |
| Alexander Harper Aviation & Security Ltd | Wholesale & retail | 2014 |
| Alexander Hughes UK Executive Search Ltd | Professional & scientific | 2020 |
| Alexander Lyons Solutions Ltd | Administrative & support | 2010 |
| Alexander Martin International Ltd | Professional & scientific | 2018 |
| Alexanderkarl Ltd | Construction | 2019 |
| Alexandra Joy ISW Limited | Health & social care | 2025 |
| Alexandra Road (Farnborough) Management Company Ltd | Households | 2017 |
| Alexein Ltd | Information & communication | 2024 |
| Alfa Dog Ltd | Other services | 2022 |
| Alfie Consulting Ltd | Other services | 2023 |
| Alfscar Holdings Ltd | Construction | 2026 |
| Alian Consult Ltd | Professional & scientific | 2024 |
| Align Growth Global UK Ltd | Professional & scientific | 2026 |
| Alignia Consulting Limited | Professional & scientific | 2023 |
| ALL Eden Garden Care Ltd | Administrative & support | 2026 |
| ALL Gear Services (1990) Limited | Manufacturing | 2003 |
| ALL Hallows Farnham Charitable Trust | Health & social care | 1994 |
| ALL Saints Court (Didcot) Freehold Company Limited | Households | 2006 |
| ALL Saints Court (Didcot) Management Company Limited | Households | 1987 |
| ALL Wheel Drive Club | Arts & recreation | 1990 |
| Allgroup Services Limited | Construction | 2022 |
| Alliance Digital Limited | Professional & scientific | 2024 |
| Alliance of Construction Networks Limited | Professional & scientific | 2012 |
| Allibone Electrical Services Limited | Construction | 2015 |
| Allimac Ltd | Real estate | 2024 |
| Allison Rodger Designs Limited | Manufacturing | 2004 |
| Allotrope Energy Ltd | Other services | 2016 |
| Allround Scaffolding Limited | Construction | 2020 |
| Allvistar Limited | Professional & scientific | 2002 |
| Allwindowsanddoors Limited | Construction | 2022 |
| Ally and MO Media Limited | Information & communication | 2018 |
| Ally Consultancy & Design Limited | Arts & recreation | 2014 |
| Ally J Steel Ltd | Information & communication | 2023 |
| Alma Film Production Ltd | Extraterritorial | 2023 |
| Almar Enterprises Limited | Financial services | 1998 |
| Alpha Beta Capital Management Limited | Professional & scientific | 2024 |
| Alphagoods Ltd | Wholesale & retail | 2022 |
| Alta Stet Limited | Professional & scientific | 2016 |
| Alternative Foods London Ltd. | Manufacturing | 2018 |
| Alternatives Skin Care Centre Limited | Other services | 2016 |
| Altius Advisors Limited | Professional & scientific | 2024 |
| Alton Psychology Ltd | Health & social care | 2026 |
| Altonovus Limited | Professional & scientific | 2015 |
| Alwood House Limited | Households | 2007 |
| AM Brand Consultancy Ltd | Professional & scientific | 2018 |
| AMA Buchanan Investments Ltd | Real estate | 2016 |
| AMA Design Limited | Professional & scientific | 2014 |
| Amade Ltd | Financial services | 2013 |
| Amaneku Limited | Financial services | 2026 |
| Amarks Limited | Information & communication | 1992 |
| Amazon Systems (1981) | | 1997 |
| AMB Foods Limited | Wholesale & retail | 1998 |
| Amba & Thorn Limited | Wholesale & retail | 2024 |
| Amber and Boon Ltd | Professional & scientific | 2022 |
| Ambertate Ltd | Real estate | 2022 |
| Ambetus Ltd | Professional & scientific | 2015 |
| AMC 26 Ltd | Health & social care | 2022 |
| AMC Partners Limited | Real estate | 2021 |
| Amena Ltd | Real estate | 2025 |
| Amigo Opportunities Limited | Financial services | 2024 |
| Amiso Marketing Ltd | Professional & scientific | 2026 |
| Amoli Consulting Limited | Professional & scientific | 2024 |
| AMP Marketing Ltd | Professional & scientific | 2016 |
| AMP Your Content Limited | Other services | 2022 |
| Amperio Services Limited | Construction | 2022 |
| AMS Financial Dynamics Limited | Financial services | 2015 |
| Amsa 1 Investment Limited | Real estate | 2025 |
| AMV Project Solutions Limited | Professional & scientific | 2024 |
| Analytical Research Ltd | Professional & scientific | 2009 |
| Anchormind Diagnostics Ltd | Extraterritorial | 2025 |