| Abacus Direct Holdings Limited | Extraterritorial | 2019 |
| Abacus Direct Limited | Extraterritorial | 2001 |
| Abacus Group (Topco) Limited | Extraterritorial | 2024 |
| Abbassi Limited | Professional & scientific | 2000 |
| Abbeydale (Newbury) Management Company Limited | Households | 2007 |
| Abbott Moody Associates Limited | Professional & scientific | 2005 |
| Abelard Management Services Limited | Professional & scientific | 2004 |
| Abgo Equipment Sales Limited | Extraterritorial | 1975 |
| ABI Llewellyn-Jones Limited | Administrative & support | 2017 |
| Abingdon Residential Properties Ltd | Real estate | 2014 |
| Abinger a Joinery Limited | Manufacturing | 2018 |
| Able Steelwork & Metalwork Ltd | Manufacturing | 2011 |
| Abode Staff Ltd | Administrative & support | 2024 |
| Abon Studio Ltd | Professional & scientific | 2026 |
| Absolute Casing Ltd. | Administrative & support | 1999 |
| Absolute Sense Learning Limited | Education | 2016 |
| Abstract Bodyworks (UK) Ltd | Arts & recreation | 2012 |
| AC Power Electric Ltd | Construction | 2023 |
| AC Walkers Ltd | Professional & scientific | 2023 |
| Academy Editions Limited | Information & communication | 2006 |
| Academy Properties Ltd | Construction | 2019 |
| Accomplish Fitness Limited | Arts & recreation | 2014 |
| Accounting & Taxation Centre Limited | Professional & scientific | 2002 |
| Accounting 24/7 Limited | Professional & scientific | 2017 |
| Accusim Ltd | Professional & scientific | 2023 |
| Ace 21 Consultancy Ltd | Professional & scientific | 2018 |
| Ace 21 Holdings Ltd | Financial services | 2018 |
| Ace 21 Property Ltd | Real estate | 2018 |
| Acies Software Limited | Information & communication | 2020 |
| ACL EOT Limited | Financial services | 2025 |
| ACN Ltd | Construction | 2025 |
| Acorn Court (Newbury) Management Company Limited | Households | 2012 |
| Acorn Development Projects Limited | Construction | 2019 |
| Acorn Health Limited | Health & social care | 2025 |
| Acorn Managed Services Ltd | Professional & scientific | 2019 |
| Acorn Removals and Storage Ltd | Transport & logistics | 2024 |
| Acorn Ridge (Newbury) Limited | Other services | 2000 |
| Acquist Limited | Financial services | 2013 |
| Acrobat Vehicle Rental Limited | Administrative & support | 1997 |
| ACS Media Limited | Wholesale & retail | 1993 |
| Actaros Consultancy Limited | Professional & scientific | 2016 |
| Action 8 Components Limited | Manufacturing | 1995 |
| Active Defence Legal Services Limited | Professional & scientific | 2017 |
| Active Heating & Cooling Services Limited | Construction | 2024 |
| Active Heating Services Ltd | Manufacturing | 1999 |
| Activetraveller Limited | Wholesale & retail | 2000 |
| Actnow House Ltd | Information & communication | 2019 |
| Acton Actuarial Limited | Other services | 2024 |
| Acute Sales Limited | Extraterritorial | 2016 |
| Acutest Test Instrument Specialists Limited | Extraterritorial | 2004 |
| Ad.Ventures London Ltd | Professional & scientific | 2012 |
| ADA Networks Limited | Information & communication | 1997 |
| Adal Studio Ltd | Administrative & support | 2026 |
| Adam Optics Ltd | Other services | 2017 |
| Adamode Optical Ltd | Health & social care | 2022 |
| Adaptive Cooling Limited | Construction | 2005 |
| Adaptive Strategies Ltd | Professional & scientific | 2022 |
| Adbury Electronics Limited | Real estate | 1987 |
| Addaesie Ltd | Professional & scientific | 2025 |
| Addison Clark Ltd | Professional & scientific | 2017 |
| Adelfas Property Group Ltd | Real estate | 2018 |
| Adept Business Systems UK Limited | Information & communication | 2015 |
| ADG Music Services Ltd | Arts & recreation | 2025 |
| ADH Installations Ltd | Construction | 2024 |
| Adhesive Specialities Limited | Manufacturing | 1969 |
| Adit Capital Advisers Limited | Other services | 2025 |
| ADJ Energy Limited | Manufacturing | 2016 |
| Adjoy Healthcare Ltd | Health & social care | 2017 |
| Adlam Associates Limited | Professional & scientific | 2013 |
| ADM91 Projects Ltd | Construction | 2026 |
| Admatica Limited | Administrative & support | 2008 |
| Adorepower Limited | Wholesale & retail | 1975 |
| ADP Forecourt Ltd | Real estate | 2025 |
| Adpp Limited | Real estate | 2019 |
| Adstar Supermart Limited | Real estate | 1995 |
| Adstock Limited | Professional & scientific | 2014 |
| Adurni Barnstaple Limited | Real estate | 2022 |
| Adurni Limited | Real estate | 2017 |
| Adurni West Limited | Real estate | 2020 |
| Advanta Internet Limited | Information & communication | 1997 |
| Advantiv Holdings Limited | Financial services | 2025 |
| Advantiv Limited | Administrative & support | 2002 |
| Advertise Limited | Information & communication | 1991 |
| Aegiscon Ltd | Information & communication | 2021 |
| Aerify Services Limited | Construction | 2014 |
| Aero Property Consultants Limited | Construction | 2020 |
| Aero Transports Ltd | Transport & logistics | 2020 |
| Aerocars Limited | Wholesale & retail | 1981 |
| Aerocropter Ltd | Information & communication | 2024 |
| Aervue Ltd | Information & communication | 2025 |
| AF Building Limited | Construction | 2021 |
| AFF Windservices UK Ltd | Energy | 2025 |
| Afon Consulting Ltd | Professional & scientific | 2023 |
| Africa Commercial Ltd | Real estate | 2014 |
| Afriera Limited | Professional & scientific | 2012 |
| Afristruct Limited | Professional & scientific | 2021 |
| AFS Consultancy Limited | Information & communication | 2008 |
| AGA Spares Limited | Extraterritorial | 2016 |
| Agentis Technologies Ltd | Financial services | 2026 |
| Agile Circuit Technology Group Ltd. | Financial services | 2024 |