| Anton Rentals Ltd | Real estate | 2015 |
| Antony Haylock Studios Limited | Arts & recreation | 2003 |
| ANY Legal Problem Limited | Professional & scientific | 2000 |
| ANY Problems Ltd. | Real estate | 1999 |
| AP8 Healthcare Solutions Limited | Administrative & support | 2016 |
| Apatura Insights Limited | Information & communication | 2023 |
| Apax Properties Ltd | Real estate | 2005 |
| APE DEE Events Ltd | Arts & recreation | 2024 |
| Apex First Response Ltd | Other services | 2024 |
| Appetites for Europe Ltd | Information & communication | 2004 |
| Applied Engineering Solutions Limited | Professional & scientific | 2001 |
| Appsora Limited | Information & communication | 2007 |
| APS Investments (UK) Limited | Administrative & support | 2014 |
| APS Mechanical Services Limited | Construction | 1994 |
| Aquatech Plumbingheating and GAS Ltd | Construction | 2004 |
| Arandi Limited | Professional & scientific | 2007 |
| Arcadia Printing Limited | Administrative & support | 2008 |
| Archi-Tone Ltd | Professional & scientific | 2003 |
| Arctic Air (UK) Limited | Administrative & support | 2005 |
| Ardentinny Management Company Limited(The) | Real estate | 1971 |
| Area Office Cleaners Limited | Administrative & support | 1964 |
| Argonaut Investments Limited | Real estate | 2021 |
| Ariadne Designs Limited | Information & communication | 2001 |
| Arion Show Jumpers Limited | Agriculture & fishing | 2007 |
| Aristo Films Limited | Arts & recreation | 1973 |
| Arji Property UK Limited | Real estate | 2020 |
| Arkinbutler Ltd | Professional & scientific | 2007 |
| Arnold & Sharp Limited | Hospitality | 1992 |
| Arnolds Osteopathy Acupuncture & Herbs Limited | Health & social care | 2002 |
| Articulates Limited | Arts & recreation | 2008 |
| Artworld United Limited | Arts & recreation | 2004 |
| ASH & Oak Limited | Other services | 2003 |
| Ashlee Accountancy Limited | Professional & scientific | 2007 |
| Ashregal Limited | Real estate | 2002 |
| Ashuranli Ltd | Wholesale & retail | 2019 |
| Ashvale Technology Ltd | Construction | 1997 |
| Ashworth Homes Limited | Construction | 1973 |
| Asli Meva Limited | Hospitality | 2026 |
| Asnu (UK) Limited | Wholesale & retail | 1990 |
| Asnu Corporation Europe Limited | Manufacturing | 1997 |
| Aspden Engineering Services Limited | Construction | 2006 |
| Asset Wealth Management Limited | Financial services | 2003 |
| Asset Wealth Management LLP | | 2003 |
| Association of Event Venues Limited | Other services | 2004 |
| Aston Grange Bengeo Management Limited | Households | 2003 |
| Astonridge Limited | Construction | 2000 |
| Astrobloomjewels Ltd | Wholesale & retail | 2025 |
| Atech Limited | Manufacturing | 1982 |
| Ategri Ltd | Education | 2005 |
| Atlas Composites Limited | Professional & scientific | 1986 |
| Atlas Distribution Services Limited | Transport & logistics | 2002 |
| Atlas Road Markings Limited | Arts & recreation | 2007 |
| Atlasim Limited | Real estate | 2017 |
| Attractive Management Limited | Real estate | 1990 |
| AU Investments Limited | Financial services | 2011 |
| Audhdefacto Ltd | Information & communication | 2026 |
| Augustus Electrical Contractors Limited | Construction | 2002 |
| AUK Investments Holdings Limited | Financial services | 2020 |
| AUK Investments Limited | Wholesale & retail | 1967 |
| Aurora Smile Studio Ltd | Real estate | 2007 |
| Austin RAY Limited | Construction | 1999 |
| Austin Trueman Checking Services Limited | Professional & scientific | 1992 |
| Austin Trueman Consulting Engineers Limited | Professional & scientific | 1991 |
| Austin Trueman Health and Safety Limited | Professional & scientific | 1995 |
| Austin Trueman International Limited | Professional & scientific | 1978 |
| Austin Trueman Limited | Professional & scientific | 1998 |
| Austin Trueman Projects Limited | Professional & scientific | 1994 |
| Austin Trueman Specialist Surveys Limited | Professional & scientific | 1992 |
| Austral Consulting Services Ltd | Professional & scientific | 2026 |
| Autobright Limited | Wholesale & retail | 2006 |
| Automotive Art Limited | Wholesale & retail | 2002 |
| Avante Healthcare Limited | Hospitality | 2007 |
| Avanti Corporation Limited | Real estate | 1996 |
| Avco Motors Limited | Wholesale & retail | 1999 |
| Avente Limited | Construction | 2004 |
| Avenue Investment Company Ltd | Extraterritorial | 1972 |
| Avgas Worldwide Limited | Wholesale & retail | 2000 |
| AVR Holdings Group Ltd | Financial services | 2025 |
| Avrmobiles.Co.Uk Limited | Wholesale & retail | 2006 |
| AWG Air Conditioning Ltd | Energy | 2017 |
| AWM Rail Ltd | Construction | 2017 |
| Axiom Force Ltd | Professional & scientific | 2021 |
| Axminster RD Limited | Real estate | 2014 |
| AY Catering Ltd | Hospitality | 2020 |
| Aybel Services Ltd | Other services | 2021 |
| Aykn Holdings Ltd | Financial services | 2024 |
| Aylett Nurseries Limited | Wholesale & retail | 1954 |
| Azlan Homes Ltd | Construction | 2005 |
| Aztec Flooring Limited | Construction | 2002 |
| Aztec Maintenance Limited | Administrative & support | 1991 |
| Azure Contracting Limited | Construction | 2022 |
| Azure Demolition Limited | Construction | 2022 |
| Azure Holdings Herts Limited | Financial services | 2022 |
| Azure Projects London Limited | Construction | 2023 |
| Azure Property Investments Limited | Construction | 2023 |
| B F Roofing & Property Maintenance Ltd | Construction | 2024 |
| B GEE Limited | Professional & scientific | 2003 |
| B Impressed Limited | Other services | 2017 |
| B J Engravers Limited | Professional & scientific | 2006 |
| B.J.R. Systems Limited | Manufacturing | 1997 |