| Affinity South East Ltd | Health & social care | 2025 |
| Afristar BIO Limited | Other services | 2019 |
| Aftd Ltd | Wholesale & retail | 2017 |
| Agency August Ltd | Hospitality | 2021 |
| Agency Bell Ltd | Administrative & support | 2011 |
| Agile Integrator Ltd | Information & communication | 2018 |
| AGM Plumbing Solutions Limited | Construction | 2026 |
| AGZ Property Investment Limited | Real estate | 2020 |
| AH Drylining Ltd | Construction | 2025 |
| Ahmad Clinical Services Limited | Health & social care | 2026 |
| AI Boost Ltd | Information & communication | 2023 |
| Ai-Bility.Io Ltd | Information & communication | 2026 |
| AIB International-Uk, Ltd | Administrative & support | 2009 |
| AIJ London Construction and Joinery Ltd | Construction | 2025 |
| AIM Internet Investments Limited | Administrative & support | 2000 |
| Air Traffic Management Consultancy Ltd | Transport & logistics | 2026 |
| Aircom International Limited | Information & communication | 1995 |
| Aircon Installations Limited | Manufacturing | 1992 |
| Aitch Care Homes (London) Limited | Administrative & support | 2004 |
| AJ Strength Ltd | Health & social care | 2023 |
| Ajca Ltd | Arts & recreation | 2025 |
| Akanbi Consulting Limited | Professional & scientific | 2022 |
| Akerns Limited | Real estate | 2024 |
| Akins Business Services Limited | Administrative & support | 2013 |
| AL Builders U.K. Limited | Construction | 2025 |
| AL Mortgage Services Ltd | Financial services | 2025 |
| Al-Basit Foods Ltd | Hospitality | 2024 |
| Alan Friend Limited | Arts & recreation | 2008 |
| Alan Thomson Couriers Limited | Transport & logistics | 2015 |
| Alboa Limited | Information & communication | 2024 |
| Albury Mill Management Company Limited | Households | 2008 |
| ALC Ultrasound Limited | Health & social care | 2026 |
| Alchemy Development Ltd | Real estate | 2026 |
| Alderbury Limited | Real estate | 2024 |
| Alderwood L.L.A. Limited | Health & social care | 1999 |
| Alex Scaffolding Ltd | Construction | 2015 |
| Alexander Kent Limited | Professional & scientific | 2008 |
| Alexandra Lodge (Guildford) RTM Co Ltd | Households | 2004 |
| Alfred Norman Limited | Information & communication | 2023 |
| Ali's Grill Limited | Hospitality | 2016 |
| Aligned for Life Limited | Health & social care | 2011 |
| Alimonjeel Limited | Hospitality | 2024 |
| Alina Care Holdings Limited | Professional & scientific | 2013 |
| Alina Care Limited | Health & social care | 2014 |
| Alina Homecare Barnet Limited | Health & social care | 2008 |
| Alina Homecare Bromsgrove Ltd | Health & social care | 2007 |
| Alina Homecare Ltd | Health & social care | 2013 |
| Alina Homecare Services Ltd | Health & social care | 2018 |
| Alina Homecare Stevenage Ltd | Health & social care | 2001 |
| Alistair Bromhead Limited | Professional & scientific | 2009 |
| ALL Fired UP Ceramics Ltd | Wholesale & retail | 2020 |
| ALL in One Maintenance Services Limited | Construction | 1998 |
| ALL Stars Cafe Community Interest Company | Hospitality | 2009 |
| ALL Things Green Landscapers Limited | Administrative & support | 2013 |
| Allan Williams Limited | Wholesale & retail | 2025 |
| Allenium Consultants Limited | Extraterritorial | 2008 |
| Allium Pubs Ltd | Hospitality | 2023 |
| Allosterica Limited | Professional & scientific | 2021 |
| Almanac House Management Company Limited | Households | 1997 |
| Almay Getaway Limited | Households | 2026 |
| Aloysious Limited | Real estate | 2017 |
| Altaclara Aviation Limited | Administrative & support | 2018 |
| Alternative Fuels Incorporated Limited | Professional & scientific | 2015 |
| Alternative Technology Limited | Water & waste | 1982 |
| Alwyne Court Owners Limited | Households | 2002 |
| Alyne Ecology Ltd | Professional & scientific | 2019 |
| Aman Services Ltd | Information & communication | 2018 |
| Amata Integrity Engineering Limited | Information & communication | 2021 |
| Amaze Finance Limited | Professional & scientific | 2015 |
| Amber Works Studios Ltd | Manufacturing | 2025 |
| AMC Cafe Ltd | Hospitality | 2017 |
| AMC Robotics Ltd | Professional & scientific | 2025 |
| Amelia Maya Miah Ltd | Hospitality | 2019 |
| AMF Furniture Ltd | Wholesale & retail | 2021 |
| Amfa Trading Ltd | Wholesale & retail | 2025 |
| AMR Plumbing & Heating Limited | Construction | 2008 |
| AN Services(Uk) Ltd | Administrative & support | 2020 |
| ANA Construction (Southern) Ltd | Construction | 2013 |
| Anacy Global Ltd | Professional & scientific | 2011 |
| Anavo Capital Limited | Real estate | 2019 |
| Anavo Care (Brampton) Limited | Health & social care | 2022 |
| Anavo Care (Crewe) Ltd | Health & social care | 2021 |
| Anavo Care (Havant) Ltd | Health & social care | 2024 |
| Anavo Care (Hove) Ltd | Health & social care | 2022 |
| Anavo Care (Lancing) Limited | Health & social care | 2021 |
| Anavo Care (Surbiton) Limited | Health & social care | 2021 |
| Anavo Care (Whitchurch) Limited | Health & social care | 2021 |
| Anavo Care Elevation II Limited | Health & social care | 2025 |
| Anavo Care Elevation Ltd | Health & social care | 2024 |
| Anavo Care Ltd | Health & social care | 2020 |
| Anavo Care Scot Ltd | Health & social care | 2023 |
| Anavo Developments Ltd | Construction | 2020 |
| Anavo Propco (Hove) Limited | Health & social care | 2025 |
| Anchor Bookham Ltd | Hospitality | 2023 |
| Ancient Replicas Ltd | Wholesale & retail | 2020 |
| Andas Consulting Limited | Mining & quarrying | 2021 |
| Andean Rose Trading Limited | Wholesale & retail | 2016 |
| Anderson Sinclair & Co LLP | | 2004 |
| Andersons of London Limited | Construction | 2015 |
| Andrew Noble Consulting Ltd | Professional & scientific | 2024 |