| Activeis Limited | Information & communication | 1997 |
| Actmac Limited | Professional & scientific | 2019 |
| Actuary Limited | Real estate | 2013 |
| Acute Management Limited | Administrative & support | 2021 |
| Acute Trustees Limited | Professional & scientific | 2004 |
| AD Astra Consultants Private Ltd | Information & communication | 2021 |
| AD Contract Cleaning Ltd | Administrative & support | 2006 |
| Adam White Landscapes Limited | Administrative & support | 2023 |
| Adamarc Group Limited | Real estate | 2019 |
| Adamsrill Close (Management) Limited | Households | 1968 |
| Adaptev Ltd | Construction | 2021 |
| Addison Scaffolding Ltd | Construction | 2018 |
| Addler Limited | Administrative & support | 2016 |
| Adeevo Limited | Professional & scientific | 2005 |
| Adevious Limited | Information & communication | 2013 |
| Adeyemi Fitness Limited | Arts & recreation | 2021 |
| Adgenz Limited | Real estate | 2020 |
| ADI Aviation Ltd | Wholesale & retail | 2023 |
| Aditiya Services Ltd | Wholesale & retail | 2023 |
| ADJ Builders Limited | Construction | 2021 |
| Adjk Property Limited | Real estate | 2023 |
| Adjk Real Estate Ltd | Real estate | 2021 |
| ADK Car Club Ltd | Administrative & support | 2021 |
| Adler Instrument Limited | Wholesale & retail | 2015 |
| Adlil Limited | Health & social care | 2021 |
| Admacro Ltd | Financial services | 2016 |
| Admin & Event Solutions Limited | Professional & scientific | 2012 |
| Adonai Caring Limited | Administrative & support | 2014 |
| Adonis Property Co. Ltd | Real estate | 2006 |
| Adonisav Ltd | Wholesale & retail | 2020 |
| Adorable Decorators and Builders Ltd | Construction | 2026 |
| Adorn and Revel Ltd | Wholesale & retail | 2023 |
| Adrian and Sons Group Limited | Construction | 2025 |
| ADS Support Limited | Administrative & support | 2016 |
| ADT Cars Limited | Wholesale & retail | 2016 |
| ADV Assets Ltd | Real estate | 2021 |
| Advanced Analytics Limited | Information & communication | 2022 |
| Advanced Cell Technologies Ltd | Professional & scientific | 2018 |
| Advanced Dental Care Limited | Administrative & support | 2012 |
| Advanced School of Management Limited | Education | 2025 |
| Advent Advocacy Limited | Professional & scientific | 2007 |
| Advent Medical Services Limited | Health & social care | 2001 |
| Advik OFF License Ltd | Wholesale & retail | 2026 |
| Advisory Prime Limited | Real estate | 2024 |
| ADZ Homes Limited | Real estate | 2024 |
| AE Group (Europe) LLP | | 2020 |
| AE Group Ltd | Real estate | 2022 |
| AEA Portmanteau Ltd | Health & social care | 2013 |
| Aedis Heating Ltd | Construction | 2020 |
| Aedis Security Systems Ltd | Administrative & support | 2016 |
| Aegis Healthcare Services Ltd | Administrative & support | 2019 |
| Aegz Franchising - SW London Limited | Hospitality | 2019 |
| Aembase Limited | Other services | 2015 |
| AEO Capital Ltd | Administrative & support | 2025 |
| AEO Investments Limited | Administrative & support | 2018 |
| AEO Property Ltd | Real estate | 2022 |
| Aeonn Ltd | Professional & scientific | 2024 |
| Aephoros Ltd | Wholesale & retail | 2023 |
| Aerial Ventures Limited | Information & communication | 2018 |
| Aerolease Services Limited | Administrative & support | 2009 |
| Aesgs Investments Ltd | Real estate | 2022 |
| Aesthetic 24 Ltd | Wholesale & retail | 2026 |
| Aesthetics-Pro Limited | Other services | 2024 |
| Aestheticus Limited | Health & social care | 2007 |
| Aesthetiva Beauty Ltd | Other services | 2020 |
| Aethra Logistics Limited | Transport & logistics | 2015 |
| AF Contractors Ltd | Construction | 2022 |
| AFC Systems Limited | Information & communication | 2008 |
| Afcc International Ltd | Other services | 2025 |
| Affectionate Care Home Limited | Health & social care | 2019 |
| Affectionate Healthcare Limited | Health & social care | 2018 |
| Affinity Global Services Ltd | Professional & scientific | 2017 |
| Affinity Twin Limited | Information & communication | 2021 |
| Afflecto Limited | Real estate | 2019 |
| AFG Investment Ltd | Real estate | 2021 |
| Afrelib Community Interest Company | Education | 2021 |
| African Enterprise UK Limited | Other services | 1979 |
| Afterset Limited | Extraterritorial | 1989 |
| Afyacore Limited | Health & social care | 2016 |
| AG & M Construction Ltd | Construction | 2021 |
| AG Contractors (London) Limited | Construction | 2019 |
| AG Novis Ltd | Administrative & support | 2026 |
| AGB Partners Ltd | Wholesale & retail | 2016 |
| Agentsx Ltd | Information & communication | 2025 |
| AGF Project Management Limited | Construction | 2021 |
| Agfan Design Limited | Wholesale & retail | 2026 |
| Aggy's INK Ltd | Arts & recreation | 2014 |
| Agileserv Ltd | Information & communication | 2023 |
| AGL Project Management Ltd | Manufacturing | 2008 |
| AGR Commercial Ltd | Professional & scientific | 2015 |
| Agrimquant Limited | Information & communication | 2026 |
| Agron Properties Ltd | Real estate | 2024 |
| Agtc Investments Ltd | Real estate | 2019 |
| Agvesto Finance Limited | Financial services | 2021 |
| Ah-R Fasades Ltd | Construction | 2020 |
| Ahara Consulting Ltd | Health & social care | 2019 |
| Ahascragh Limited | Other services | 2016 |
| Ahead of Time Global Events Limited | Arts & recreation | 2017 |
| Ahinsa Limited | Wholesale & retail | 2025 |
| Ahmet&Alya Properties Limited | Real estate | 2024 |