| Anna Nails Maidenhead Ltd | Other services | 2024 |
| Anna Verghese Consulting Ltd | Administrative & support | 2018 |
| Annyco Holdings Limited | Wholesale & retail | 2016 |
| Annyco Ltd | Financial services | 2016 |
| Anomis Consulting Ltd | Other services | 2017 |
| Anselmi Limited | Construction | 2024 |
| Ansh Ventures Ltd | Professional & scientific | 2026 |
| Anthony Noyce Design Limited | Professional & scientific | 2018 |
| Anthony Paul Designer Goldsmith Limited | Other services | 2008 |
| Antinoro Commercials Limited | Wholesale & retail | 2022 |
| Anto Ventures Ltd | Wholesale & retail | 2021 |
| Anto&Fab Construction Ltd | Construction | 2023 |
| Anwita Limited | Information & communication | 2012 |
| ANX Distribution Ltd | Wholesale & retail | 2026 |
| ANY Freight Movements Ltd | Water & waste | 2010 |
| AOU Investments Limited | Financial services | 2024 |
| APB Consulting and Training Limited | Real estate | 2019 |
| APD Car Executive Limited | Other services | 2023 |
| Apex Design & Construction Limited | Construction | 2001 |
| Apex Electrical and Alarms Limited | Professional & scientific | 2001 |
| Apex Engineering and Controls Ltd | Construction | 2026 |
| Apex Financial Services & Wealth Management Ltd | Financial services | 2021 |
| Apex Matrix Ltd | Households | 2025 |
| Apex Quant Ltd | Information & communication | 2020 |
| Apex Services Group Limited | Construction | 2002 |
| Apex Trade London Ltd | Wholesale & retail | 2019 |
| Apexshine Ltd | Administrative & support | 2026 |
| Apmn Ltd | Wholesale & retail | 2025 |
| Apna Bridge Super Store Limited | Wholesale & retail | 2011 |
| Apnac (Pizza) Limited | Hospitality | 1992 |
| Apnac Limited | Wholesale & retail | 2004 |
| Apodi Healthcare Limited | Health & social care | 2012 |
| Apodi Limited | Administrative & support | 2006 |
| Apollo Security Ltd | Administrative & support | 2022 |
| Apple Garden Homes Ltd | Real estate | 2019 |
| Appleby Group Limited | Financial services | 1951 |
| Applegarth Care Home Limited | Health & social care | 2010 |
| Appleseed Properties Limited | Construction | 2018 |
| Appleton Commercial Services Limited | Water & waste | 2012 |
| Appleton Commercial Vehicles Limited | Wholesale & retail | 2022 |
| Appleton Landscapes Limited | Administrative & support | 2023 |
| Applied Accounting Limited | Professional & scientific | 2022 |
| Applied Heating and Cooling Limited | Construction | 2023 |
| Applied Legal Services Limited | Professional & scientific | 2017 |
| Applied Magnetics Limited | Professional & scientific | 2009 |
| Applied Medical Products Limited | | 1983 |
| Applitech Consultancy Ltd | Professional & scientific | 2013 |
| Appnovate Solutions Limited | Information & communication | 2009 |
| Appreciating Time Group Limited | Wholesale & retail | 2019 |
| Apprenticeshop CIC | Wholesale & retail | 2023 |
| Approved Fencing Limited | Construction | 2024 |
| Approved Paving and Resin Limited | Construction | 2022 |
| Apps Business IT Solutions UK Ltd | Information & communication | 2018 |
| Apptitude Coaching & Consulting Limited | Professional & scientific | 2026 |
| APQ Developments Group Limited | Construction | 2008 |
| Apraze Ltd | Information & communication | 2005 |
| APROPERJOB4U Ltd | Construction | 2022 |
| APW Asset Management Ltd | Wholesale & retail | 2002 |
| Aqua Therapy Marine Charters LLP | | 2008 |
| Aquabrite Ltd | Administrative & support | 2017 |
| Aquadrill Ltd | Manufacturing | 2002 |
| Aquapark Reading Limited | Arts & recreation | 2019 |
| Aquarius Luxury Concierge Ltd | Administrative & support | 2018 |
| AR Golf Ltd | Other services | 2018 |
| Ar&G Ltd | Construction | 2024 |
| Arabian Oryx Ltd | Wholesale & retail | 2025 |
| Arba Trading Ltd | Wholesale & retail | 2025 |
| Arbin Business Solutions Limited | Professional & scientific | 2004 |
| ARC Aggregates Limited | Professional & scientific | 1956 |
| ARC Building Limited | Professional & scientific | 1958 |
| ARC Concrete (Anglia) Limited | Professional & scientific | 1968 |
| ARC Concrete Limited | Professional & scientific | 1941 |
| ARC Holdings Limited | Professional & scientific | 1925 |
| ARC Land Holdings Limited | Professional & scientific | 1955 |
| ARC Limited | Professional & scientific | 1956 |
| ARC Property Investments Limited | Professional & scientific | 1930 |
| ARC Slimline Limited | Professional & scientific | 1920 |
| ARC South Wales Limited | Professional & scientific | 1972 |
| ARC South Wales Mortar Limited | Professional & scientific | 1935 |
| ARC South Wales Quarries Limited | Financial services | 1963 |
| ARC South Wales Surfacing Limited | Professional & scientific | 1964 |
| Arcane Motors Ltd | Wholesale & retail | 2025 |
| Arcbaygroup Ltd | Professional & scientific | 2025 |
| Arcforce Welding Ltd | Manufacturing | 2025 |
| Archanis Ltd | Information & communication | 2025 |
| Archers Rugs Limited | Wholesale & retail | 2025 |
| Archigrace Ltd | Construction | 2013 |
| Archis Solutions Limited | Information & communication | 2008 |
| Archit Pharma Innovations Limited | Wholesale & retail | 2011 |
| Architecture Development Holdings Ltd | Real estate | 2018 |
| Archum Limited | Construction | 2025 |
| Arcon Properties Limited | Administrative & support | 1996 |
| Arcturus IT Services Ltd. | Information & communication | 2015 |
| Arde Operation and Process Consultancy Ltd | Professional & scientific | 2019 |
| Ardenix Holdings Ltd | Energy | 2026 |
| Ardent Developments (Europe) Ltd | Construction | 2020 |
| Arembe Limited | Manufacturing | 2001 |
| Argofield Limited | Wholesale & retail | 1993 |
| Aria Consultancy and Trading Limited | Wholesale & retail | 2023 |
| Aria DD Ltd | Extraterritorial | 2024 |