| Amment Risk Consulting Limited | Wholesale & retail | 2013 |
| Amou Saam Ltd | Hospitality | 2020 |
| Ampy Amersham Ltd | Professional & scientific | 2025 |
| Ampy Amersham Park Ltd | Professional & scientific | 2025 |
| Amsk Technologies Limited | Information & communication | 2018 |
| AMU Holdings Limited | Information & communication | 2021 |
| AMU Properties Ltd | Real estate | 2022 |
| AN Design and Build Limited | Construction | 2018 |
| Anbukudil Ltd | Real estate | 2021 |
| Andelain Limited | Professional & scientific | 2002 |
| Ando Plumbing Ltd | Construction | 2020 |
| Andob Property Development Limited | Real estate | 2018 |
| Andrew Massey Limited | Information & communication | 2012 |
| Andrew Mold LLP | | 2012 |
| Andsow Solutions Ltd | Health & social care | 2020 |
| Angelovi Electrical Ltd | Construction | 2017 |
| Anglo Irish Property Co (A.I.P.C.) Limited | Real estate | 1972 |
| Angrez Ventures Ltd | Financial services | 2017 |
| ANJ Analytics Limited | Information & communication | 2023 |
| ANJ Housing Limited | Real estate | 2024 |
| Annamax Limited | Professional & scientific | 2020 |
| Annant Light Haulage Ltd | Transport & logistics | 2026 |
| Anne Marie Dancy Ltd | Professional & scientific | 2025 |
| Annex Infotech Limited | Information & communication | 2024 |
| Annicchiarico Digital Services Ltd | Information & communication | 2024 |
| Annks Estate Ltd | Real estate | 2013 |
| ANP Training & Consultancy Limited | Professional & scientific | 2019 |
| Antardhwani (UK) Ltd | Education | 2023 |
| Antonio C Martinez Web Limited | Wholesale & retail | 2025 |
| Anukira Limited | Wholesale & retail | 2020 |
| Anymanandvan Ltd | Transport & logistics | 2024 |
| AP Shine Ltd | Health & social care | 2023 |
| Apex Events Limited | Information & communication | 2017 |
| Apoy Properties Ltd | Real estate | 2017 |
| Appaca Ltd | Information & communication | 2013 |
| Appleyard Aviation Limited | Transport & logistics | 2023 |
| Apps Machinery Transport Ltd | Transport & logistics | 2019 |
| Apptradesolutions Ltd | Information & communication | 2015 |
| Apstech Advisors Limited | Professional & scientific | 2021 |
| Aquasar UK Limited | Information & communication | 2025 |
| ARA Dental Care Ltd | Health & social care | 2014 |
| ARA Dental Implants Ltd | Professional & scientific | 2014 |
| ARA Property Management Ltd | Real estate | 2014 |
| Arabella Rose Hair Ltd | Other services | 2024 |
| Arbora Arborists Limited | Agriculture & fishing | 2025 |
| Architecture Solutions Ltd | Information & communication | 2012 |
| Arcicon Limited | Professional & scientific | 2006 |
| ARD Medical Limited | Health & social care | 2011 |
| Ardwear Ltd | Wholesale & retail | 2024 |
| Ared (London) Limited | Construction | 2013 |
| Ares Homes Limited | Real estate | 2025 |
| Aria Healthcare Consulting Limited | Professional & scientific | 2013 |
| Aries Management Limited | Professional & scientific | 2009 |
| Arina Enterprises Ltd | Construction | 2018 |
| ARK 2024 Ltd | Real estate | 2024 |
| Armstrong Fleming Ltd | Information & communication | 2026 |
| Armstrong Technologies Ltd | Information & communication | 2024 |
| Arockia IT Solutions Limited | Information & communication | 2012 |
| Arran Gregory Ltd | Arts & recreation | 2014 |
| Artio Accountants Limited | Professional & scientific | 2016 |
| Arunar Property Ltd | Real estate | 2024 |
| Arunar PVT Ltd | Construction | 2014 |
| ARV Smile Limited | Health & social care | 2026 |
| AS & NS Consultants Ltd | Health & social care | 2023 |
| Asbestos and Environmental Consultants Ltd | Professional & scientific | 2014 |
| ASC Building Contractors Ltd | Construction | 2020 |
| Asco Foods Limited | Wholesale & retail | 2000 |
| Asco Residential Limited | Construction | 2001 |
| ASH Maguire Coaching Limited | Other services | 2019 |
| ASH Mill Amersham Court Limited | Real estate | 2016 |
| ASH Mill Boxmoor LLP | | 2014 |
| ASH Mill Developments Limited | Construction | 1996 |
| ASH Mill Northgate LLP | | 2013 |
| ASH Mill South Hams Limited | Real estate | 2011 |
| Ashford Flowers Ltd | Wholesale & retail | 2020 |
| Ashley Streather Horology Ltd | Wholesale & retail | 2021 |
| Ashmead Place Management Limited | Real estate | 2004 |
| Asianook Ltd | Hospitality | 2026 |
| Askk Real Estates Limited | Real estate | 2021 |
| ASL Digital Limited | Information & communication | 2023 |
| ASM Infotech Limited | Information & communication | 2025 |
| Asset Planning Solutions Limited | Financial services | 2009 |
| Asta Homes Ltd | Real estate | 2024 |
| Astrealm Accounting Limited | Professional & scientific | 2014 |
| Atelier Lighting Ltd | Manufacturing | 2018 |
| Athelstone Consultants Limited | Information & communication | 2011 |
| Atkinsons Consulting (UK) Limited | Professional & scientific | 2007 |
| Atlas Enterprises Ltd | Real estate | 2019 |
| Atlas Oceanway Homes Ltd | Real estate | 2026 |
| ATM Drywall Ltd | Construction | 2011 |
| Atomlink Education LLP | | 2026 |
| Atomlink Limited | Other services | 2017 |
| Atomlink Services LLP | | 2022 |
| ATP Accountants Ltd | Extraterritorial | 2020 |
| Atsd Zeyyl Ltd | Wholesale & retail | 2025 |
| Attitude Personal Management Limited | Professional & scientific | 2009 |
| ATW Enterprises Limited | Professional & scientific | 2025 |
| Aura Executive Solutions Limited | Transport & logistics | 2025 |
| Aura N Limited | Financial services | 2014 |
| Aurabella Ltd | Wholesale & retail | 2025 |