| A2B Plumbing & Bathrooms Limited | Construction | 2025 |
| A6144 Self Storage Limited | Transport & logistics | 2025 |
| AA MCR Limited | Health & social care | 2025 |
| AA Smiles Ltd | Health & social care | 2022 |
| AA Tooth Holdings Ltd | Health & social care | 2024 |
| AA1 Medical Services Ltd. | Health & social care | 2013 |
| AA9 Properties Ltd | Real estate | 2024 |
| AAA23 Ltd | Hospitality | 2025 |
| Aanitec Ltd | Information & communication | 2018 |
| Aarambh Investments (AI) Ltd | Real estate | 2022 |
| Aarnis Ltd | Real estate | 2023 |
| AB Consultants (ABC) Ltd | Professional & scientific | 2021 |
| AB Home Textiles Ltd | Wholesale & retail | 2017 |
| Abakua Construction Ltd | Construction | 2024 |
| Abbey Change Solutions Ltd | Information & communication | 2019 |
| Abby Carm Ltd | Health & social care | 2024 |
| Abdaldayim Neuroscience Services Ltd | Health & social care | 2023 |
| Abihealth Enterprises Ltd | Health & social care | 2019 |
| Abihome Properties Limited | Real estate | 2020 |
| Abihomes Ltd. | Real estate | 2018 |
| Abimed Support Services Ltd | Health & social care | 2015 |
| Abiw Property Limited | Real estate | 2016 |
| Able Thai Kitchen Ltd | Hospitality | 2025 |
| ABODE360 Ltd | Real estate | 2024 |
| ABODE4 Ltd | Real estate | 2022 |
| Abridge Technologies Ltd | Information & communication | 2015 |
| ABS Brymar Floors (UK) Limited | Construction | 2001 |
| ABS Brymar Floors Limited | Construction | 1984 |
| Absalute Garments Design Ltd | Wholesale & retail | 2025 |
| Absolute Granite Care Limited | Administrative & support | 2009 |
| Absolute North West Limited | Construction | 2019 |
| Abushamah Medics Ltd | Health & social care | 2016 |
| AC Leisure Ltd | Other services | 2012 |
| Academy SBI Limited | Information & communication | 2026 |
| Accel Software Services Limited | Information & communication | 2013 |
| Acceloron Limited | Information & communication | 2017 |
| Accessory Emporium Ltd | Wholesale & retail | 2019 |
| Accountancy & Tax Services (UK) Limited | Professional & scientific | 2015 |
| Accountancy Anywhere Limited | Professional & scientific | 2013 |
| Accountancyplace Ltd | Professional & scientific | 2023 |
| Ace Aluminium & Architectural Services Ltd | Construction | 2011 |
| Ace Compliance Group Ltd | Construction | 2021 |
| Ace Spaces Property Ltd | Real estate | 2024 |
| Ace Supply Company Limited(The) | Manufacturing | 1986 |
| Acelab Tutors Ltd | Education | 2025 |
| ACK Properties (NW) Ltd | Real estate | 2024 |
| ACM Partnership Limited | Professional & scientific | 2013 |
| ACM Studios Limited | Other services | 2022 |
| Acquiesce Technical Solutions Limited | Mining & quarrying | 2015 |
| Acra Developments Limited | Construction | 2019 |
| Acre Wood Nursery School Ltd | Education | 2011 |
| ACS Thermal Engineers Limited | Professional & scientific | 1990 |
| ACS4U Limited | Professional & scientific | 2008 |
| ACT Digital Ltd | Information & communication | 2014 |
| ACT NOW Consultancy Limited | Professional & scientific | 2012 |
| Action International (Manchester) Limited | Transport & logistics | 2002 |
| Action Productions Ltd | Information & communication | 2014 |
| Actis Recruitment Limited | Administrative & support | 2003 |
| Activate Sports Therapy Ltd | Health & social care | 2018 |
| Activelyoutdoors Ltd | Information & communication | 2018 |
| Acuhealth Clinic Ltd | Health & social care | 2018 |
| Acute GPS Ltd | Health & social care | 2018 |
| AD Line Entertainment Limited | Information & communication | 1999 |
| AD Line Partners Limited | Arts & recreation | 2023 |
| AD Lumina Consulting Ltd | Health & social care | 2026 |
| Adam Lyne Limited | Information & communication | 2015 |
| Adamoli Consulting Limited | Professional & scientific | 2023 |
| Adams-Edwards Property Solutions Limited | Households | 2021 |
| Addictive Digital Ltd | Professional & scientific | 2024 |
| Addmee Transport Ltd | Other services | 2021 |
| ADE Recruitment Group Limited | Extraterritorial | 2020 |
| ADE Recruitment Limited | Administrative & support | 1999 |
| Ade-Oye UK Enterprises Ltd | Administrative & support | 2014 |
| Adelphi Castle Limited | Professional & scientific | 1999 |
| Adelphi Wharf One Management Ltd | Real estate | 2019 |
| Adepto Technical Recruitment Limited | Administrative & support | 2015 |
| Adhd Rentals Limited | Real estate | 2026 |
| Adhikari Ltd | Hospitality | 2023 |
| Adimus Limited | Financial services | 2011 |
| Adlexandra Limited | Real estate | 2023 |
| Administrative Services International Limited | Financial services | 2015 |
| Adurisoft Limited | Administrative & support | 2016 |
| Advance Building & Window (UK) Limited | Construction | 2022 |
| Advanced GAS and Heating Limited | Construction | 2009 |
| Advanced Motors Ltd | Wholesale & retail | 2023 |
| Advantage Media Consulting Ltd | Professional & scientific | 2024 |
| Adynaton Asset Management LLP | | 2016 |
| Adynaton Partners LLP | | 2016 |
| Aegismb Limited | Health & social care | 2025 |
| AEM House Ltd | Real estate | 2025 |
| Aesh Marketing Solutions Ltd | Wholesale & retail | 2023 |
| AF Car Sales Ltd | Wholesale & retail | 2024 |
| Affordable Hairs Ltd | Wholesale & retail | 2025 |
| AG Facades Limited | Construction | 2009 |
| Agai Business Solutions Limited | Transport & logistics | 2023 |
| Agency PSI Limited | Professional & scientific | 2019 |
| Agenzia 14 National Limited | Wholesale & retail | 2017 |
| Agenzia 14 Northern Limited | Construction | 2016 |
| Agga Investments Limited | Real estate | 2021 |
| AGH Management Limited | Construction | 2024 |