| Aces Property Limited | Real estate | 2013 |
| ACJ UK Limited | Real estate | 1992 |
| ACT4THEATRE Limited | Arts & recreation | 2024 |
| Active Auto Locksmith Limited | Manufacturing | 2025 |
| Acton Motors Limited | Professional & scientific | 1945 |
| Acumagic Medical Limited | Wholesale & retail | 2021 |
| Acutepoint Medical Ltd | Health & social care | 2025 |
| Acwp Ltd | Wholesale & retail | 2020 |
| AD Chef Ltd | Professional & scientific | 2024 |
| Ad.Con Europe Ltd | Professional & scientific | 2010 |
| Adam Accounts Limited | Professional & scientific | 2010 |
| Adama Consulting Limited | Professional & scientific | 2009 |
| Adapt Technology Limited | Information & communication | 1991 |
| Adara Maison Limited | Households | 2025 |
| ADD a Space Ltd. | Construction | 2012 |
| Addfluence Ltd | Professional & scientific | 2025 |
| Adendra Therapeutics Limited | Professional & scientific | 2021 |
| Adeza Care Homes Limited | Health & social care | 1997 |
| Adlee Exterior Cleaning Ltd | Administrative & support | 2025 |
| Adria Exclusive Ltd | Professional & scientific | 2014 |
| ADT Services Ltd | Professional & scientific | 2026 |
| Adtech Investments Limited | Financial services | 2020 |
| Adult Education Employment & Training Limited | Education | 2018 |
| Advanced Fleet Support Ltd | Other services | 2022 |
| Advanced Global Consulting - London Ltd | Administrative & support | 2015 |
| Adventure With Easha Ltd | Information & communication | 2023 |
| Advisory and Consulting Services LLP | | 2020 |
| Adwalker (UK) Limited | Professional & scientific | 2004 |
| AE Creative Studio Limited | Arts & recreation | 2026 |
| Aedifix Ltd | Construction | 2018 |
| Aeelo Ltd | Wholesale & retail | 2020 |
| Aegis & Trident Capital Limited | Financial services | 2021 |
| Aerocontrols Air Conditioning Ltd | Construction | 2025 |
| Aeronyte Solutions Ltd | Professional & scientific | 2025 |
| Aeterna Power Limited | Administrative & support | 2024 |
| Aether Events Limited | Hospitality | 2020 |
| Aetheria Group Ltd | Professional & scientific | 2023 |
| AEZ Properties Ltd | Real estate | 2016 |
| AFE Construction Services Limited | Construction | 2017 |
| AFE Consulting Limited | Administrative & support | 2018 |
| AFE Developments Limited | Real estate | 2017 |
| AFE Recruitment Limited | Administrative & support | 2011 |
| AFE Staffing Solutions Limited | Administrative & support | 2018 |
| Affiliate Internet Marketing Limited | Information & communication | 2017 |
| Affinity Bar Limited | Hospitality | 2003 |
| Affinity Independent Financial Solutions Ltd | Financial services | 2015 |
| Affinity Resource Group Limited | Information & communication | 2015 |
| Afocus Ltd | Information & communication | 2025 |
| Afterglow 136 Limited | Other services | 2017 |
| AG Dance Limited | Arts & recreation | 2017 |
| AG Electrical Services (London) Ltd | Construction | 2024 |
| AG Ethan Limited | Health & social care | 2020 |
| AGD Property Ltd | Real estate | 2024 |
| Agent Jones LLP | | 2019 |
| Agent X Limited | Real estate | 2002 |
| Aggies Vipooches Ltd | Other services | 2025 |
| Aggregate Movements Logistics Limited | Water & waste | 2026 |
| AGH Partners UK Ltd | Professional & scientific | 2025 |
| AGI Assets Ltd | Financial services | 2026 |
| AGJ Electrical Ltd | Construction | 2022 |
| AGL Construction & Maintenance (London) Limited | Construction | 2021 |
| AGM Bishops Limited | Transport & logistics | 2020 |
| AGM Relocation Limited | Transport & logistics | 2014 |
| AGO Holdings Ltd | Hospitality | 2020 |
| AGP Scaffold Ltd | Construction | 2022 |
| AGS Corporation Ltd | Administrative & support | 2013 |
| AH UK Holdings Ltd | Real estate | 2017 |
| AHC Promotions Ltd | Other services | 2023 |
| AI Business Consulting Ltd | Information & communication | 2023 |
| AI Made Easy Ltd | Information & communication | 2023 |
| Aida Trading Consultancy Services Limited | Administrative & support | 2020 |
| Aiex Asset Management Ltd | Real estate | 2023 |
| Aiex Ltd | Wholesale & retail | 2013 |
| Air Fusion Ltd | Administrative & support | 2017 |
| Airshow Ltd | Professional & scientific | 2023 |
| Aishvar Properties Limited | Real estate | 2021 |
| Aiskineres Ltd | Information & communication | 2026 |
| Aisleyne Limited | Arts & recreation | 2006 |
| Aisthetics Ltd | Other services | 2021 |
| AIT Connections Limited | Information & communication | 1995 |
| AJ Dental Care Ltd | Health & social care | 2023 |
| AJ Properties Investment Limited | Real estate | 2021 |
| AJC Concepts Ltd | Professional & scientific | 2025 |
| AJL Media Productions Ltd | Information & communication | 2019 |
| Ajlp Holdings Limited | Real estate | 2020 |
| Ajones IT Consulting Ltd | Information & communication | 2018 |
| Ajoshi Consultancy Ltd | Professional & scientific | 2024 |
| AJP & DJP Ltd | Real estate | 2026 |
| AJS Music Limited | Arts & recreation | 2013 |
| AK Dental and Cosmetic Services Ltd | Health & social care | 2026 |
| AK Global Solutions Limited | Information & communication | 2015 |
| AKB Tech Ltd | Information & communication | 2023 |
| AKB Tiling Limited | Construction | 2017 |
| Akhtar Professional Services Limited | Professional & scientific | 2014 |
| Akilans Limited | Wholesale & retail | 2013 |
| Akon Enterprises Ltd | Construction | 2001 |
| Alam Consultants Limited | Professional & scientific | 2017 |
| Alan & EVY Ltd | Transport & logistics | 2019 |
| Alazomer Limited | Other services | 2025 |
| Albiz Packaging Ltd | Manufacturing | 2017 |