| Alex RAW Limited | Information & communication | 2016 |
| Alex Weeks Editing Ltd | Information & communication | 2013 |
| Alexa Co. Limited | Professional & scientific | 2003 |
| Alexander & Associates Accountants Ltd | Professional & scientific | 2008 |
| Alexander Automobiles Ltd | Wholesale & retail | 2026 |
| Alexander Electrical Services Limited | Construction | 2006 |
| Alexander Opticians Limited | Wholesale & retail | 2022 |
| Alexander Thomas Associates Limited | Other services | 2012 |
| Alexander Woolfe Commercial Agents Ltd | Real estate | 2018 |
| Alexandra Road (Enfield) Management Company Limited | Households | 1986 |
| Alexgardener 2023 Ltd | Administrative & support | 2023 |
| Alexyan Limited | Professional & scientific | 2016 |
| Alfer Consultants Ltd | Administrative & support | 2023 |
| Alford House (Management) Limited | Administrative & support | 1982 |
| Alford House Freehold Ltd | Real estate | 2020 |
| Alfrankie Limited | Construction | 2021 |
| Alfred Saxon Limited | Real estate | 1994 |
| Alfreton Fabrications Limited | Manufacturing | 2005 |
| Algomit Ltd | Information & communication | 2025 |
| ALI Amer Ltd | Construction | 2019 |
| ALI Tutor Ltd | Education | 2025 |
| Aliaj Building Ltd | Manufacturing | 2026 |
| Alice Moore Design Ltd | Professional & scientific | 2020 |
| Alice Project LAB Ltd | Manufacturing | 2026 |
| Alice Webster Interiors Limited | Other services | 2010 |
| Alicora Limited | Wholesale & retail | 2026 |
| Alim and Humairaa Limited | Hospitality | 2019 |
| Aline Leonello Ltd | Information & communication | 2021 |
| Alium Cleaning Services Ltd | Administrative & support | 2019 |
| Aljabir & Co. Ltd | Professional & scientific | 2013 |
| Aljan Group Ltd | Financial services | 2020 |
| ALK Radiology Solutions Limited | Health & social care | 2025 |
| Alkioni Holdings Ltd | Financial services | 2017 |
| Alkioni Properties Ltd | Real estate | 2020 |
| Alkor Capital Limited | Financial services | 2010 |
| ALL About Care South West Limited | Health & social care | 2008 |
| ALL Alex Ltd | Construction | 2021 |
| ALL Boxed UP Media Limited | Administrative & support | 2013 |
| ALL Business Finance Ltd | Administrative & support | 2024 |
| ALL Displays Limited | Administrative & support | 2009 |
| ALL Gone Ltd | Water & waste | 2009 |
| ALL Humanity Limited | Education | 2016 |
| ALL in Removals & Storage Limited | Transport & logistics | 1999 |
| ALL in Therapy Ltd | Health & social care | 2024 |
| ALL Metal Solutions Limited | Manufacturing | 2011 |
| ALL Store 21 Ltd | Wholesale & retail | 2018 |
| ALL Things Licensing Limited | Professional & scientific | 2007 |
| ALL Time Locksmith Limited | Wholesale & retail | 2013 |
| Allen and Brown Limited | Construction | 2012 |
| Allengrantpartners Limited | Information & communication | 2026 |
| Allergymedic Limited | Health & social care | 2016 |
| Alleyfit Ltd | Arts & recreation | 2014 |
| Allfixed Ltd | Real estate | 2018 |
| Alliance Kapital Ltd | Professional & scientific | 2021 |
| Alliance Protection and Facilities Management Ltd | Administrative & support | 2016 |
| Allied Boards Ltd | Other services | 2020 |
| Allwin Smith Consultancy Limited | Professional & scientific | 2022 |
| Alma Exchange Limited | Professional & scientific | 2024 |
| Almedalo Ltd | Professional & scientific | 2013 |
| Almend Limited | Health & social care | 2025 |
| Alminas Hands on Limited | Professional & scientific | 2016 |
| Almira Assets Holdings Ltd | Financial services | 2023 |
| Almoha Ltd | Information & communication | 2014 |
| Alora Concepts Limited | Professional & scientific | 2025 |
| Alpha Automotive Associates Limited | Extraterritorial | 2008 |
| Alpha Heat Limited | Construction | 2003 |
| Alpha Heat Servicing Ltd | Construction | 2012 |
| Alpha Home Improvements Ltd | Construction | 2021 |
| Alpha Plumbing Group Ltd | Construction | 2025 |
| Alphabet Interiors Ltd | Construction | 2014 |
| Alphacube Limited | Real estate | 2017 |
| Alphagreen Group Limited | Information & communication | 2019 |
| Alphaside Limited | Other services | 2025 |
| Alphasymbol Limited | Real estate | 1984 |
| Alpine Metals PLC | Professional & scientific | 2006 |
| Alpine Partners UK LLP | | 2014 |
| Alpri. Home Ltd | Wholesale & retail | 2024 |
| Alsamor Limited | Real estate | 2022 |
| Alston Jones Electrics Limited | Construction | 2015 |
| Alston Work Studio Ltd | Arts & recreation | 2023 |
| Altair Property Investments Limited | Real estate | 2023 |
| Alto Architecture Ltd | Professional & scientific | 2016 |
| Altus Global Consulting Limited | Administrative & support | 2020 |
| Aluminium Doors and Windows Ltd | Manufacturing | 2020 |
| AM Bespoke Construction Ltd | Other services | 2019 |
| AM Black Ltd | Professional & scientific | 2011 |
| AM Design & Build Arch Limited | Construction | 2025 |
| AM Healthcare Consultancy Ltd | Health & social care | 2017 |
| AM UK Consulting Ltd | Professional & scientific | 2015 |
| AMA IT Solutions Ltd | Information & communication | 2019 |
| Amafhhmas Limited | Manufacturing | 2017 |
| Amal Mental Health Limited | Administrative & support | 2021 |
| Amalfi P.I. Limited | Manufacturing | 2025 |
| Amara Designs (Potters Bar) Limited | | 1971 |
| Amara Investments 2023 LLP | | 2023 |
| Amas (Two) LLP | | 2015 |
| Amauk Ltd | Information & communication | 2023 |
| Amazing Grace Home Care Ltd | Health & social care | 2023 |
| Amazing Taste Ltd | Hospitality | 2025 |
| Amba Traders Ltd | Hospitality | 2021 |