| Akeron (U.K.) Limited | Manufacturing | 1959 |
| AKG Scaffolding Ltd | Construction | 2025 |
| Akira Reid Limited | Arts & recreation | 2019 |
| Akranet Limited | Hospitality | 2022 |
| AKS Fitting Ltd | Administrative & support | 2024 |
| Akuk Merchants Ltd | Wholesale & retail | 2025 |
| AL Hilal Limited | Extraterritorial | 1998 |
| AL Kaif Ltd | Wholesale & retail | 2025 |
| AL Mahata Limited | Wholesale & retail | 2004 |
| Al-Aqsa World Foods Limited | Wholesale & retail | 2025 |
| Al-Muhtadun Ltd | Education | 2021 |
| Alan Chenery Carpets Limited | Other services | 2003 |
| Alan J Kidd Mechanical Engineering Ltd | Manufacturing | 2001 |
| Alan Pudney Limited | Agriculture & fishing | 1959 |
| Alavan Limited | Other services | 2003 |
| Alayna Noor Limited | Wholesale & retail | 2019 |
| Alblair Consulting Ltd | Information & communication | 2006 |
| Alchemy Data Solutions Limited | Information & communication | 2004 |
| Alderton Hill Properties Limited | Real estate | 1964 |
| Aldon Ltd. | Hospitality | 2001 |
| Alebiosu Health Limited | Health & social care | 2024 |
| Alenacrafts Ltd | Wholesale & retail | 2025 |
| Alex Page Ltd | Professional & scientific | 2019 |
| Alexander Court (Epping) Management Company Limited | Real estate | 2001 |
| Alexander Heights Residents Management Company Limited | Households | 2000 |
| Alexander Master Holdings Ltd | Extraterritorial | 2022 |
| Alexander Property Leasing Ltd | Real estate | 2021 |
| Alexandra House (Leigh) Limited | Wholesale & retail | 2006 |
| Alexenea Logistic Ltd | Transport & logistics | 2018 |
| Alexian Homes Limited | Construction | 2007 |
| Alexis Business Supports Limited | Administrative & support | 2006 |
| Aleye Limited | Information & communication | 2006 |
| Alfatah Logistics Limited | Transport & logistics | 2021 |
| Alfen Consultants Limited | Professional & scientific | 2005 |
| Alfred Graham Limited | Wholesale & retail | 1980 |
| ALI Baba Deals Ltd | Wholesale & retail | 2025 |
| ALI Consultants Limited | Professional & scientific | 2014 |
| ALI Firat Aydogan Ltd | Wholesale & retail | 2025 |
| ALI Veg&Fruit Ltd | Wholesale & retail | 2024 |
| Ali's Bangla Kitchen Ltd | Hospitality | 2022 |
| Ali.Ay Investments Ltd | Real estate | 2022 |
| Alice Dadson Limited | Wholesale & retail | 2025 |
| Alifu Ltd | Information & communication | 2025 |
| Alkhattab for General Trading Limited | Wholesale & retail | 2025 |
| ALL 2 C Limited | Construction | 2007 |
| ALL City Services Ltd | Administrative & support | 2025 |
| ALL Clean Services Limited | Administrative & support | 1994 |
| ALL Mechanical Solutions Limited | Construction | 2021 |
| ALL Season Vibe Limited | Wholesale & retail | 2026 |
| ALL Things Craft Beer Limited | Wholesale & retail | 2021 |
| Allegro Music Essex | | 1991 |
| Allen Bros. (Electrical Factors) Limited | Wholesale & retail | 1972 |
| Allen Brothers (Fittings) Limited | Manufacturing | 1958 |
| Allguards Safety Engineering Limited | Water & waste | 1979 |
| Alliance for Development of Tamil Language, Culture & Heritage | Education | 2021 |
| Allied Media Marketing Limited | Information & communication | 2019 |
| Allimax Tools Ltd | Wholesale & retail | 2021 |
| Allisade Limited | | 1987 |
| Alloway Technology Ltd | Wholesale & retail | 2012 |
| Allsafely IT Services Ltd | Information & communication | 2026 |
| Alltrades Group Ltd | Construction | 2019 |
| Allweathers Limited | Wholesale & retail | 2006 |
| Allwell Control Systems Limited | | 1981 |
| Allyuh Ltd | Wholesale & retail | 2026 |
| Alma Engineering Xcel Limited | Manufacturing | 2022 |
| Almaco U.K. Limited | | 1986 |
| ALN Trans Ltd | Transport & logistics | 2019 |
| Aloka Health Limited | Health & social care | 2026 |
| Alone With GOD Ministries Ltd | Education | 2019 |
| Alpha Electrical Services Limited | Wholesale & retail | 1973 |
| Alpha Garden Centre Limited | Professional & scientific | 1980 |
| Alphabeta Health Limited | Health & social care | 2025 |
| Alpi UK Limited | Transport & logistics | 1990 |
| Alpi United Kingdom Limited | Transport & logistics | 1993 |
| Alpine Taxis Limited | Transport & logistics | 1998 |
| Alsane Ltd | Wholesale & retail | 2025 |
| Alsava Limited | Information & communication | 2022 |
| Alto Nominees Limited | Professional & scientific | 1992 |
| Altstep Ltd | Education | 2025 |
| Alulie Limited | Households | 2005 |
| Alumaflex Limited | Extraterritorial | 2004 |
| Aluminium Pulleys Limited | Professional & scientific | 1969 |
| Aluuva Limited | Financial services | 2013 |
| Alvexon Ltd | Wholesale & retail | 2026 |
| ALY Construction Ltd | Construction | 2024 |
| Amaal Ltd | Wholesale & retail | 2014 |
| Amac Construction Limited | Construction | 2007 |
| Aman Media Ltd | Other services | 2025 |
| Amana Trust | Other services | 2002 |
| Amaoko Limited | Health & social care | 2026 |
| Amar Construction Ltd | Wholesale & retail | 2002 |
| Amaxus IT Ltd | Information & communication | 2013 |
| Amazing Grace Ltd | Health & social care | 2024 |
| Amazing Happiness Limited | Health & social care | 2025 |
| Amazing World Ltd | Wholesale & retail | 2024 |
| AMAZINGPLACES2B Ltd | Real estate | 2021 |
| AMB Concept Limited | Wholesale & retail | 2024 |
| AMB Global Limited | Information & communication | 2007 |
| AMB Service Solutions Ltd | Real estate | 2025 |
| Ambareen Ltd | Wholesale & retail | 2006 |