| Actit Holdings Limited | Professional & scientific | 2025 |
| Active MED Supplies Ltd | Administrative & support | 2020 |
| Activlives | Health & social care | 2011 |
| Acunova Acupuncture Limited | Education | 2025 |
| Acuro Snagging Limited | Construction | 2022 |
| Acutax Limited | Professional & scientific | 2026 |
| Acutebeauty Limited | Other services | 2024 |
| ACW Electrical Suffolk Ltd | Manufacturing | 2013 |
| AD Busu Ltd | Hospitality | 2022 |
| AD Entertainment LAB Limited | Information & communication | 2021 |
| AD Service Holbrook Ltd | Health & social care | 2023 |
| Ad-Ex Group Ltd | Construction | 2026 |
| Adaben TS Ltd | Transport & logistics | 2025 |
| Adal Seco Limited | Manufacturing | 1996 |
| Adam & EVE (Hairdressers) Limited | Other services | 2017 |
| Adam Cars Ipswich Ltd | Wholesale & retail | 2026 |
| Adam Gemili Limited | Arts & recreation | 2012 |
| Adam Green Windows Ltd | Wholesale & retail | 2022 |
| Adamben TS Ltd | Transport & logistics | 2025 |
| Adamou Ltd | Professional & scientific | 2011 |
| Adams Ellis Ltd | Information & communication | 2021 |
| Adapt Limited | Professional & scientific | 1997 |
| Adbh Advisory Limited | Professional & scientific | 2021 |
| ADC Leisure Ltd | Hospitality | 2019 |
| Adderley Freight Management Ltd | Transport & logistics | 2026 |
| Aden UK Property Limited | Real estate | 2025 |
| Adjustable Polymers Ltd | Water & waste | 2018 |
| Adler & Oak Limited | Real estate | 2019 |
| ADM Accountants Limited | Professional & scientific | 2012 |
| ADM Developments Ltd | Real estate | 2007 |
| ADM Property Co 1 Limited | Real estate | 2019 |
| ADM Transport Ltd | Transport & logistics | 2018 |
| Admedtransport Ltd | Transport & logistics | 2025 |
| Administer Limited | Administrative & support | 2012 |
| Admiral Home Improvements Ltd | Construction | 2022 |
| Admiralty Pier Management Company Limited | Households | 2019 |
| ADO Consulting Ltd | Professional & scientific | 2020 |
| Adore Nature Limited | Wholesale & retail | 2019 |
| Adored Sports & Entertainment Ltd | Administrative & support | 2017 |
| Adri Hoxhalli Ltd | Transport & logistics | 2023 |
| Adrian & Iwona Ltd | Water & waste | 2017 |
| Adrian Fagg Holdings Limited | Financial services | 2025 |
| Adrian Hart Cars Limited | Wholesale & retail | 2012 |
| Adrian Haulage Ltd | Transport & logistics | 2023 |
| Adrian Nebunu Ltd | Administrative & support | 2017 |
| Adrian Peck Limited | Administrative & support | 2024 |
| Adrian Saunders Decorators Limited | Construction | 2002 |
| Adrian Williams Transport Limited | Transport & logistics | 2009 |
| Adroit Accountants Limited | Professional & scientific | 2018 |
| Adroit Assets Limited | Real estate | 2020 |
| Adroit Careplus Ltd | Health & social care | 2024 |
| ADS Plumbing Ltd | Construction | 2016 |
| Adsar Limited | Information & communication | 2009 |
| Adusoby Ltd | Health & social care | 2021 |
| ADV Digital Solutions Ltd | Professional & scientific | 2022 |
| Advance Digital Graphics Limited | Administrative & support | 1980 |
| Advance Edification Ltd | Professional & scientific | 2020 |
| Advance Heating Limited | Manufacturing | 2016 |
| Advanced Dent Repairs Limited | Wholesale & retail | 2003 |
| Advanced Distribution Logistics Limited | Transport & logistics | 2011 |
| Advanced Marketing (Europe) Limited | Financial services | 1997 |
| Advanced Water Services Limited | Construction | 2025 |
| Advantage Angels Care Limited | Health & social care | 2020 |
| Advantage Angels Ltd | Health & social care | 2017 |
| Adventine Ltd | Information & communication | 2025 |
| Adventure Medix Limited | Education | 2015 |
| Advion Ltd | Manufacturing | 2001 |
| Advised Executive Ltd | Professional & scientific | 2019 |
| ADW Studios Limited | Professional & scientific | 2024 |
| Adzilla Ltd | Professional & scientific | 2025 |
| AE Diagnostics Ltd | Health & social care | 2019 |
| AE Markovc Limited | Arts & recreation | 2022 |
| AE Residential Investments Limited | Real estate | 2023 |
| AE Site Products Ltd | Construction | 2014 |
| Aegisra UK Ltd | Administrative & support | 2026 |
| AEJ Property Ltd | Real estate | 2026 |
| AEL Homes Ltd | Real estate | 2023 |
| Aera Healthcare Limited | Health & social care | 2023 |
| Aero Dynamic Consulting Limited | Administrative & support | 2016 |
| Aero Friend Ltd | Wholesale & retail | 2017 |
| Aerocore Innovations Ltd | Manufacturing | 2025 |
| Aerofinity Ltd | Information & communication | 2020 |
| Aerographic UK Ltd | Professional & scientific | 2023 |
| Aeroguard Consulting Ltd | Professional & scientific | 2026 |
| Aeronautical Consulting and Valuation Limited | Wholesale & retail | 2003 |
| Aerotech (Suffolk) Limited | Manufacturing | 2017 |
| AES National Limited | Construction | 2011 |
| Aeset Ltd | Health & social care | 2020 |
| Aesthetics Collective Limited | Extraterritorial | 2020 |
| Aesthetics SOC Ltd | Other services | 2026 |
| Aether Universal Ltd | Information & communication | 2025 |
| Aetheris Trading Limited | Wholesale & retail | 2026 |
| Aetrex Company Ltd | Wholesale & retail | 2025 |
| AF Assets Limited | Arts & recreation | 2025 |
| Afazmart Limited | Wholesale & retail | 2025 |
| Afenoid International (UK) Ltd | Information & communication | 2023 |
| Affinity PR Limited | Administrative & support | 2011 |
| Affy Films Ltd | Information & communication | 2018 |
| AFL Cosmetic Solutions Limited | Wholesale & retail | 2016 |
| Aflh Fish and Chips Ltd | Hospitality | 2024 |