| ACM Acoustic Engineering Limited | Manufacturing | 1993 |
| ACM Food Trading Ltd | Hospitality | 2024 |
| Acoustica (Europe) Ltd | Professional & scientific | 2001 |
| Acquire Property Portfolio Ltd | Real estate | 2017 |
| ACR Executive Search Ltd | Administrative & support | 2023 |
| ACR Trades and Labour Ltd | Other services | 2026 |
| Acrezone Limited | Real estate | 1984 |
| ACT London Group Ltd | Wholesale & retail | 2026 |
| Acton Gardens LLP | | 2009 |
| Acuk Property Limited | Real estate | 2024 |
| Acuro Home Improvements Ltd | Construction | 2023 |
| AD Scope Limited | Professional & scientific | 2024 |
| Adagio School of Dance Limited | Education | 2014 |
| Adair Group Ltd | Financial services | 2018 |
| Adalliance Ltd | Information & communication | 2018 |
| Adam Plumbing & Construction Limited | Construction | 2025 |
| Adam Staples Ltd | Professional & scientific | 2014 |
| Adamas Telecoms Limited | Professional & scientific | 2019 |
| Adammo Limited | Professional & scientific | 2017 |
| Adapt Consulting Ltd | Administrative & support | 2005 |
| Adasdevpro Ltd | Professional & scientific | 2018 |
| Adastra Label Marketing Company Limited | Wholesale & retail | 1973 |
| Adder Digital Technology Limited | Information & communication | 1999 |
| Adebanjo Equity Holdings Ltd | Financial services | 2025 |
| Adekams Care Services Limited | Health & social care | 2016 |
| Adflex Limited | Information & communication | 1991 |
| ADI London Ltd | Construction | 2018 |
| Admd Limited | Professional & scientific | 2010 |
| Admiral Bars (Basildon) Limited | Hospitality | 2015 |
| Admiral Bars (Chelmsford) Ltd | Hospitality | 2016 |
| Admiral Bars (Hampshire) Ltd | Hospitality | 2020 |
| Admiral Bars (Herts) Ltd | Hospitality | 2020 |
| Admiral Bars (Watford) Limited | Hospitality | 2014 |
| Admiral Leisure Ltd | Hospitality | 2023 |
| Adon Film and TV Ltd | Information & communication | 2025 |
| ADP Consulting & Engineering Ltd | Professional & scientific | 2023 |
| Adrian Phillips Land Ltd | Professional & scientific | 2026 |
| Adrs Properties Ltd | Real estate | 2017 |
| ADS Events and Promotions Ltd | Information & communication | 2016 |
| ADS on Air Ltd | Information & communication | 2025 |
| Adshaya Limited | Transport & logistics | 2009 |
| ADT Rail Ltd | Construction | 2017 |
| Advanced Clinical Conferencing Ltd | Administrative & support | 2024 |
| Advanced Resin (Group) Limited | Construction | 2019 |
| Advanced Systems Management Ltd | Information & communication | 2003 |
| Advantage Sales Coaching Ltd | Professional & scientific | 2021 |
| Advantedge Limited | Professional & scientific | 2016 |
| Adventure Under Sail | Education | 2008 |
| Aedes Rivus Real Estate Ltd | Real estate | 2024 |
| Aem-Uk Ltd | Real estate | 2025 |
| Aero Travel Groups Limited | Administrative & support | 2019 |
| Aerona Clinical Limited | Wholesale & retail | 2016 |
| Aesthetics by Charlotte Limited | Other services | 2022 |
| Aesthetics by Frances Furlong Limited | Health & social care | 2011 |
| Aesthetk Ltd | Health & social care | 2024 |
| Aethr Ltd | Wholesale & retail | 2025 |
| AFB Mechanical Ltd | Construction | 2021 |
| Affiliate Squared Holdings Limited | Financial services | 2019 |
| Affiliate Squared Ltd | Information & communication | 2011 |
| Affiliate Squared Projects Ltd | Real estate | 2019 |
| Affirm Clothing Company Limited | Wholesale & retail | 2025 |
| Afflation Ltd | Real estate | 2021 |
| Affordable EV Charging Solutions Limited | Construction | 2023 |
| Africa Nouveau Investment Ltd | Wholesale & retail | 2019 |
| Africa RE Consultants Limited | Professional & scientific | 2019 |
| Afterglow Electrical Limited | Construction | 2022 |
| AG Developments (Oxfordshire) Ltd | Construction | 2022 |
| AG Essex Limited | Other services | 2021 |
| AG Herts Limited | Other services | 2020 |
| Agantis Limited | Information & communication | 2020 |
| AGC Designing Ltd | Professional & scientific | 2020 |
| AGD Electrical Limited | Construction | 2024 |
| Agee Engineering Ltd | Manufacturing | 2019 |
| Ageless Cosmetics Ltd | Professional & scientific | 2017 |
| Aggie and Sons Company Limited | Health & social care | 2012 |
| AGL Global Ltd | Extraterritorial | 2014 |
| Aglaya Nova Ltd | Administrative & support | 2016 |
| Agmr Limited | Extraterritorial | 2016 |
| Agouti Pest Control Ltd | Agriculture & fishing | 2010 |
| Agridata Limited | Information & communication | 2011 |
| Aguila Capital Limited | Information & communication | 2009 |
| AH Steel Detailing Limited | Construction | 2020 |
| AHD Accessories Ltd | Information & communication | 2019 |
| AHG Group Holdings Limited | Financial services | 2026 |
| AHS Group Ltd | Administrative & support | 2023 |
| AI Cloud Pods Ltd | Information & communication | 2020 |
| AI Digital Healthcare Limited | Health & social care | 2019 |
| AI Stepplay Limited | Information & communication | 2025 |
| AIF Enterprises Limited | Transport & logistics | 2014 |
| Ainsley Assets Limited | Real estate | 2020 |
| Air Sports Network Ltd | Arts & recreation | 2013 |
| Aircool UK Limited | Construction | 2007 |
| Aircraft Environmental Recycling Solutions Ltd | Water & waste | 2013 |
| Airport Executive Chauffeur London Limited | Transport & logistics | 2020 |
| Airport Perishable Handling Ltd | Transport & logistics | 2017 |
| Airport Runs Limited | Transport & logistics | 2025 |
| Aiscalpshading Ltd | Other services | 2025 |
| AJ Collections Ltd | Wholesale & retail | 2003 |
| AJ Logistics & Storage Ltd | Transport & logistics | 2024 |
| AJA Motors Ltd | Wholesale & retail | 2023 |