| AC & C Shipping Ltd | Transport & logistics | 2016 |
| Acacias Lodge Residents Company Limited | Households | 1993 |
| Academy of Cake Decorating Ltd | Education | 2015 |
| Accelerate Trade Ltd | Wholesale & retail | 2026 |
| Accord Management Ltd | Real estate | 2019 |
| Ace Web Solutions Ltd | Professional & scientific | 2024 |
| Aced Properties Ltd | Real estate | 2015 |
| Achu Ltd | Administrative & support | 2026 |
| ACLER8 Ltd | Professional & scientific | 2025 |
| ACS Utility Services Limited | Administrative & support | 2017 |
| Action CAM Limited | Other services | 2018 |
| Active B Ltd | Construction | 2026 |
| Actt Ltd | Information & communication | 2025 |
| Adam Brett Winkler Retail Ltd | Wholesale & retail | 2025 |
| Adam Properties Investments Limited | Real estate | 2025 |
| Adams Land and Planning Ltd | Professional & scientific | 2023 |
| Adaption Services Limited | Construction | 2016 |
| Adaptis Solutions Limited | Information & communication | 2004 |
| Adazs Ltd | Wholesale & retail | 2025 |
| Adcom International | | 1974 |
| ADD Trans Ltd | Transport & logistics | 2022 |
| ADF Trans Ltd | Transport & logistics | 2026 |
| ADI Aayu Limited | Real estate | 2024 |
| ADJ Properties Limited | Real estate | 2009 |
| ADL Electrics Limited | Construction | 2024 |
| ADM Vehicle Solutions Limited | Wholesale & retail | 2026 |
| Adonis Motor Group Ltd | Wholesale & retail | 2023 |
| Adrian Danila Limited | Transport & logistics | 2018 |
| Adrian Serv Ltd | Transport & logistics | 2019 |
| ADV Construction Limited | Construction | 2017 |
| Advanced Car Care (Welwyn) Limited | Wholesale & retail | 2011 |
| Advanced Collection Systems Limited | Information & communication | 2000 |
| ADY F Ltd | Construction | 2015 |
| Adzosha Ltd | Information & communication | 2025 |
| Affinity Water Capital Funds Limited | Financial services | 1991 |
| Affinity Water East Limited | Financial services | 1991 |
| Affinity Water Finance (2004) PLC | Financial services | 2004 |
| Affinity Water Finance PLC | Financial services | 2018 |
| Affinity Water Holdco Finance Limited | Financial services | 2017 |
| Affinity Water Holdings Limited | Financial services | 2013 |
| Affinity Water Limited | Water & waste | 1990 |
| Affinity Water Pension Trustees Limited | Financial services | 2012 |
| Affinity Water Southeast Limited | Professional & scientific | 1992 |
| Affordable Cleaning Services Ltd | Administrative & support | 2011 |
| Afnan Dawood Ltd | Wholesale & retail | 2025 |
| African Art for Spaces Ltd | Wholesale & retail | 2020 |
| Afro Portuguese Cuisine Ltd | Hospitality | 2024 |
| Afrorganic Foods Limited Limited | Hospitality | 2014 |
| Afta Nadeem Ltd | Wholesale & retail | 2023 |
| After Alice Limited | Wholesale & retail | 2015 |
| Aftermap Ltd | Professional & scientific | 2022 |
| AGH Consultants Services Ltd | Construction | 2022 |
| Agogo's Limited | Hospitality | 2012 |
| Agrippal Limited | Professional & scientific | 2011 |
| Ahmed Capital Investments Ltd | Real estate | 2025 |
| AI Education & Tech (UK) Ltd | Professional & scientific | 2020 |
| Ailey Investments Limited | Financial services | 2022 |
| Air Business Limited | Transport & logistics | 1986 |
| Air Luxury Store Ltd | Wholesale & retail | 2024 |
| Airah Enterprise Ltd | Hospitality | 2024 |
| Aircraft Engineering Ltd | Professional & scientific | 2018 |
| Airstone Limited | Real estate | 2014 |
| Airstone Properties Limited | Real estate | 2020 |
| Ajjc Accountancy Ltd | Professional & scientific | 2026 |
| AJP Accountancy Ltd | Professional & scientific | 2013 |
| Akharsha Properties Ltd | Real estate | 2021 |
| Akin Bravura Ltd | Professional & scientific | 2013 |
| AKK Consultants Limited | Professional & scientific | 2000 |
| Akmb Ltd | Wholesale & retail | 2024 |
| Akountin Professionals Ltd | Professional & scientific | 2025 |
| Aksa Design Ltd | Administrative & support | 2015 |
| Akson Lilah Ltd | Wholesale & retail | 2025 |
| AL Appliance Repairs Ltd | Other services | 2023 |
| AL Communications Ltd | Information & communication | 2009 |
| AL Madina Halal Ltd | Wholesale & retail | 2024 |
| Al,S Specialist Cleaning Services Limited | Administrative & support | 2025 |
| AL1 Construction Services Limited | Construction | 2023 |
| AL10 Property Management Limited | Real estate | 2024 |
| Alapanla Ltd | Administrative & support | 2013 |
| Alar Construction Ltd | Construction | 2019 |
| Alatede Snacks and Foods Limited | Manufacturing | 2019 |
| Alaw Technologies Limited | Information & communication | 2022 |
| Alaya PVT Limited | Information & communication | 2022 |
| Alban Court Management Company Limited | Households | 2015 |
| Albans Motors Ltd | Wholesale & retail | 2025 |
| Aldermans Close (Dixons Hill Road) Management Limited | Other services | 1970 |
| Aledya Ltd | Transport & logistics | 2017 |
| Aleksandar P&Y Ltd | Manufacturing | 2024 |
| Alex Delivery Services UK Limited | Transport & logistics | 2024 |
| Alexander Green Offices Limited | Wholesale & retail | 2019 |
| Alexandra Court (Oakwood) Property Management Co Limited | Households | 1963 |
| Alexandra Sampson Limited | Health & social care | 2025 |
| Alfa Omega Cars Ltd | Wholesale & retail | 2020 |
| Alfie Watts Ltd | Other services | 2024 |
| Alian Property Management Ltd | Real estate | 2020 |
| Alimardee Limited | Real estate | 2016 |
| Alio Forte Limited | Construction | 2019 |
| Alio Limited | Transport & logistics | 1985 |
| Alivan Transport Ltd | Professional & scientific | 2019 |
| ALL Activity Ltd | Transport & logistics | 2026 |