| ALP Domestic Ltd | Administrative & support | 2024 |
| Alpha Arboriculture Ltd | Construction | 2022 |
| Alpha Chai Limited | Health & social care | 2025 |
| Alpha Flex 2.0 Ltd | Professional & scientific | 2024 |
| Alpha Moore Auto Limited | Wholesale & retail | 2019 |
| ALS Cleaning Solutions Ltd | Administrative & support | 2024 |
| ALS Structural Ltd | Construction | 2024 |
| Alsondesiree Ltd | Health & social care | 2014 |
| ALT WIS Limited | Transport & logistics | 2017 |
| Altonian Developments Ltd | Construction | 2025 |
| Alt’S Builders Limited | Manufacturing | 2024 |
| Alumet Tooling Limited | Financial services | 2024 |
| Alves Chapman Property Limited | Real estate | 2025 |
| Always Together Property Services Limited | Administrative & support | 2025 |
| AM Dalton Ltd | Construction | 2022 |
| AM Health & Performance Ltd | Education | 2021 |
| Amal M. Rose Solutions Ltd | Professional & scientific | 2025 |
| Amanda & Amelia Ltd | Real estate | 2020 |
| Amarisa Ltd | Real estate | 2021 |
| Amavid Property Management Ltd | Real estate | 2020 |
| AMB Glazing Ltd | Construction | 2012 |
| AMB Professional Services Ltd | Administrative & support | 2019 |
| Ambadi Tech Consultancy Services Ltd | Information & communication | 2019 |
| Amber Phillips Ltd | Professional & scientific | 2020 |
| Amberin FUR and Associates Limited | Health & social care | 2015 |
| AMD Construction and Renovation Limited | Construction | 2017 |
| American RV Club (1993) Ltd | Other services | 2023 |
| Amersham (OPS) Limited | Real estate | 2023 |
| AMF Construction Limited | Construction | 2023 |
| Amicusdan Site Services Limited | Construction | 2008 |
| Amila Autos Limited | Manufacturing | 2025 |
| Amingaon Property Company Limited | Real estate | 1959 |
| Amiow Limited | Construction | 2020 |
| Amity Developments (London) Limited | Administrative & support | 2017 |
| AMJ CTR Ltd | Construction | 2019 |
| Amrano Limited | Information & communication | 2006 |
| Amunday Electrical Ltd | Professional & scientific | 2017 |
| Amyshousechildminding Ltd | Education | 2025 |
| AN Electrical Solutions Ltd. | Manufacturing | 2020 |
| Anadolu Catering Limited | Other services | 2012 |
| ANB Business Solutions Limited | Professional & scientific | 2024 |
| Anchard Holding Ltd | Financial services | 2020 |
| Anchorpoint Investments Ltd | Real estate | 2026 |
| Ancient Genus Ltd | Financial services | 2025 |
| AND Alchemy Ltd | Health & social care | 2023 |
| Anderson Roofing Services Limited | Construction | 2008 |
| Andrew Leonard Properties Limited | Administrative & support | 2004 |
| Andy James & Sons Ltd | Wholesale & retail | 2025 |
| Andy Massey Music Services Limited | Administrative & support | 2010 |
| Angela Portelly Dentist Limited | Health & social care | 2016 |
| Angela Tina Bird Limited | Extraterritorial | 2021 |
| Angelz Aesthetics Ltd | Health & social care | 2021 |
| ANH Properties Estate Ltd | Real estate | 2025 |
| Annabro Ltd | Financial services | 2025 |
| Anne Fields Limited | Real estate | 2025 |
| Anne Mcintosh Consulting Limited | Professional & scientific | 2015 |
| Annie Davison Limited | Administrative & support | 2024 |
| Anoushka Designs Ltd | Administrative & support | 2023 |
| Anthill Housing Ltd | Real estate | 2021 |
| Anthony's Barbers Limited | Other services | 2025 |
| Anthrobotanica Limited | Health & social care | 2013 |
| Antigua Clothing Ltd | Wholesale & retail | 2024 |
| Anytime Autoglaze Ltd | Construction | 2022 |
| Aobestos Compliance Ltd | Construction | 2025 |
| AOC Site Engineering Ltd | Construction | 2026 |
| Aonwd Limited | Construction | 2016 |
| AP Firm Limited | Professional & scientific | 2024 |
| Apex CM Limited | Construction | 2018 |
| Apex Condition Ltd | Health & social care | 2014 |
| Apex Contractors Limited | Construction | 1997 |
| Apex H&S Services Limited | Professional & scientific | 2025 |
| Apex Holdings UK Limited | Financial services | 2007 |
| Apiz Ltd | Public administration | 2023 |
| App-Econ Ltd | Professional & scientific | 2019 |
| Apple & Way Limited | Health & social care | 2005 |
| Apulia Markets Ltd | Wholesale & retail | 2026 |
| Apulia Properties Limited | Administrative & support | 2017 |
| Aquakids Limited | Education | 2019 |
| Aquasan Limited | Administrative & support | 2003 |
| Aquila Community Engagement CIC | Arts & recreation | 2023 |
| Aquila Events Management Ltd | Education | 2019 |
| Aquila Sports and Education Ltd | Arts & recreation | 2019 |
| Aquila Strategic Group Limited | Real estate | 2022 |
| Aquila T.K.D Limited | Arts & recreation | 2014 |
| ARB Repairs Limited | Wholesale & retail | 2018 |
| ARC Trading Limited | Wholesale & retail | 2023 |
| Arcadd Limited | Real estate | 2011 |
| Architectural Decorators Limited | Construction | 1944 |
| Ardent Sidcup Ltd | Health & social care | 2024 |
| Arena Europe Limited | Administrative & support | 2016 |
| Arena Property Ltd | Real estate | 2018 |
| Argent Medical Ltd | Health & social care | 2025 |
| Arien Contractors Limited | Construction | 1996 |
| Arion Fire Solutions Ltd | Manufacturing | 2018 |
| Arion House International Limited | Professional & scientific | 2022 |
| Arisaviewtour Ltd | Extraterritorial | 2025 |
| ARJ Plumbing & Heating Limited | Construction | 2019 |
| ARK Automotive Storage Ltd | Transport & logistics | 2019 |
| Arli.U Limited | Construction | 2013 |
| Armour Hart Group Ltd | Construction | 1996 |