| Actseum International Limited | Wholesale & retail | 2016 |
| Actseum Limited | Wholesale & retail | 2006 |
| Actus Compliance LLP | | 2020 |
| Acumen Designers & Architects Limited | Professional & scientific | 2002 |
| Acyapinsa Limited | Information & communication | 2011 |
| AD Astra Training Ltd | Education | 2023 |
| AD Locums Ltd | Health & social care | 2016 |
| AD Manum Property Ltd | Real estate | 2016 |
| AD Retailing Limited | Wholesale & retail | 2026 |
| Ad.Plasterers Ltd | Manufacturing | 2025 |
| ADA (Hudds) Ltd | Wholesale & retail | 2019 |
| ADA Management Ltd | Financial services | 2019 |
| Adagio Systems Limited | Information & communication | 2013 |
| Adam and Co. Holdings Limited | Real estate | 2024 |
| Adam and Co. Investments Limited | Financial services | 2021 |
| Adam Daniels Pet Orthopaedics Ltd | Professional & scientific | 2024 |
| Adam Fire Surrounds Limited | Extraterritorial | 2003 |
| Adam Gill Studio Ltd | Arts & recreation | 2012 |
| Adam Target Properties Ltd | Real estate | 2018 |
| Adam's Home Store Ltd | Wholesale & retail | 2020 |
| Adams BIA Assessments Ltd | Health & social care | 2022 |
| Adams Properties Investment Ltd | Real estate | 2023 |
| Adapt My Ride Ltd | Manufacturing | 2024 |
| Adaptchain Ltd. | Manufacturing | 2020 |
| Adcam Electromotive Ltd | Arts & recreation | 2017 |
| Addington Manor Estates Limited | Agriculture & fishing | 2018 |
| Addventure Awards Limited | Education | 2008 |
| Addy Engineering Services Ltd | Water & waste | 2014 |
| Adeel Pharms Ltd | Health & social care | 2018 |
| Adelitran Ltd. | Transport & logistics | 2018 |
| Adelpha Limited | Health & social care | 2023 |
| Adenzai Healthcare Ltd | Health & social care | 2022 |
| Adeps Lanae Limited. | Extraterritorial | 1972 |
| Adept Design Ltd | Professional & scientific | 2022 |
| Adept Live Limited | Professional & scientific | 2018 |
| Adept Yorkshire Ltd | Manufacturing | 2017 |
| Adeptclub Ltd | Arts & recreation | 2022 |
| ADG Engineering Limited | Professional & scientific | 2001 |
| ADH Electrical Projects Ltd | Construction | 2014 |
| Adhd Assessment and Medication Limited | Health & social care | 2025 |
| Adil Ahmed Ltd | Health & social care | 2021 |
| ADM Residential Limited | Real estate | 2017 |
| Admin & Financial Controls Ltd | Administrative & support | 2011 |
| Admiral Labels and Print Limited | Manufacturing | 1999 |
| Admtech Ltd | Information & communication | 2022 |
| Adndigital Limited | Professional & scientific | 2016 |
| Adnen Ltd | Wholesale & retail | 2023 |
| Adon Financial Planning Limited | Professional & scientific | 2011 |
| Adrian Birkhead Plumbing & Heating Ltd | Construction | 2011 |
| Adroni Ltd | Professional & scientific | 2020 |
| ADS Kitchen Fitters Limited | Construction | 2021 |
| Adson Heating Services Limited | Construction | 2020 |
| Adtrailers Limited | Professional & scientific | 2019 |
| ADV Data Holding Limited | Financial services | 2023 |
| ADV Technical Services Limited | Administrative & support | 2012 |
| Advance Claims UK Ltd | Professional & scientific | 2008 |
| Advanced Agri-Tech Solutions Ltd | Information & communication | 2020 |
| Advanced Doors Limited | Extraterritorial | 1997 |
| Advanced Flooring Limited | Professional & scientific | 1997 |
| Advanced Professional Projects Limited | Construction | 2020 |
| Advanced Wires Ltd | Manufacturing | 2018 |
| Advani Properties LLP | | 2011 |
| Advantage Computers Limited | Information & communication | 2004 |
| Adventoris Ltd | Information & communication | 2012 |
| ADW Electrical Solutions Limited | Construction | 2017 |
| Adwest Steering Ltd | Extraterritorial | 2025 |
| ADY KO Ltd | Hospitality | 2021 |
| AE Interiors Ltd | Manufacturing | 2022 |
| AED Transformation and Consulting Limited | Professional & scientific | 2016 |
| Aeep Ltd | Administrative & support | 2017 |
| Aegb Ltd | Health & social care | 2021 |
| Aegis 48 Limited | Extraterritorial | 2018 |
| Aegis Eagles Security Services Ltd | Financial services | 2021 |
| Aerd Ltd | Professional & scientific | 2022 |
| Aerobox Ltd | Professional & scientific | 2024 |
| Aerobox Technologies Ltd | Professional & scientific | 2024 |
| Aesop Therapy Ltd | Public administration | 2026 |
| Aesthetics and Beauty Limited | Other services | 2025 |
| Aesthetics by Sabina Ltd | Other services | 2026 |
| Aesthetics by Sarah Williams Ltd | Other services | 2019 |
| Aesthetics Lounge by Sana Ltd | Other services | 2024 |
| AESTHETICS365 Wholesale Ltd | Wholesale & retail | 2024 |
| AET Holdings Limited | Administrative & support | 2009 |
| Aether Wear Ltd | Wholesale & retail | 2025 |
| AF Medical Ltd | Health & social care | 2019 |
| AFC Huddersfield Town Limited | Arts & recreation | 2003 |
| Afcz MC Holdings Ltd | Wholesale & retail | 2026 |
| Aferion Global Ltd | Wholesale & retail | 2026 |
| Affleck Care Limited | Health & social care | 2014 |
| Affordable Roofing & Property Maintenance Ltd | Construction | 2022 |
| Affordablestairlifts Limited | Manufacturing | 2017 |
| Affy Financial Limited | Health & social care | 2012 |
| AFH Logistics Ltd | Wholesale & retail | 2022 |
| AFH Management & Consulting Ltd | Real estate | 2021 |
| AFK Property Solutions Ltd | Real estate | 2026 |
| AFK Software Ltd | Information & communication | 2025 |
| Aflex Hose Limited | Manufacturing | 1972 |
| Afrimarket Group Ltd | Wholesale & retail | 2026 |
| Afro-Jireh Foodstore Ltd | Wholesale & retail | 2023 |
| Afrosouq Ltd | Wholesale & retail | 2025 |