| Adrian Gibbons Racing Ltd | Arts & recreation | 2015 |
| Adriatica Ltd | Other services | 2023 |
| Adsaemmos Limited | Construction | 2015 |
| Adsasose Ltd | Hospitality | 2022 |
| ADT Air Conditioning Ltd | Construction | 2006 |
| Adundara Services Ltd | Health & social care | 2023 |
| Adunni & Aduki Ltd | Wholesale & retail | 2020 |
| Advance Blended Concepts Ltd | Wholesale & retail | 2025 |
| Advance Careprovider Limited | Health & social care | 2023 |
| Advance Food Limited | Manufacturing | 2005 |
| Advance Network Solutions (UK) Ltd | | 2001 |
| Advance Plumbing Solutions LLP | | 2011 |
| Advanced Biomass Solutions Limited | Manufacturing | 2017 |
| Advanced Cloud Tech Limited | Information & communication | 2012 |
| Advanced Developments by Design Limited | Real estate | 2021 |
| Advanced Glazing Systems Limited | Manufacturing | 2004 |
| Advanced Industrial Technology Corporation Limited | Other services | 1993 |
| Advanced Mechanical Services Limited | Construction | 2004 |
| Advanced Painting Contractors Ltd | Administrative & support | 2016 |
| Advancevisionco Ltd | Wholesale & retail | 2025 |
| Advent Tutors Limited | Education | 2023 |
| Adverto Healthcare Ltd. | Health & social care | 2014 |
| Advocate Finance Limited | Financial services | 2005 |
| Aegissec Ltd | Administrative & support | 2025 |
| Aejz Limited | Other services | 2018 |
| Aelegance Ltd | Wholesale & retail | 2024 |
| Aeon Clothing Limited | Wholesale & retail | 1994 |
| Aervon Ltd | Wholesale & retail | 2026 |
| Aerzen Machines Limited | Manufacturing | 1973 |
| Aesthetic Cart Ltd | Extraterritorial | 2024 |
| AF Investment Properties Ltd | Construction | 2020 |
| Afabidi Medical Enterprise Limited | Health & social care | 2025 |
| Afakhade Ltd | Health & social care | 2008 |
| Affiliate Marketing 3.0 LLP | | 2025 |
| Affwebs Limited | Information & communication | 2024 |
| Afonja Trading Company Limited | Wholesale & retail | 2025 |
| Afreen's Kitchen Ltd | Hospitality | 2025 |
| Africa & Caribbean Counter Terrorism, Security and Legislatures' Academy UK Limited | Financial services | 2019 |
| African Shop Harlow Ltd | Manufacturing | 2020 |
| Afro-Salopian Medic Ltd | Health & social care | 2024 |
| Afrobiz Network Ltd | Administrative & support | 2022 |
| Afrojem Ltd | Manufacturing | 2008 |
| Afrotrade Limited | Financial services | 2007 |
| Afshaar Ltd | Wholesale & retail | 2026 |
| Aftab Offerz Ltd | Wholesale & retail | 2026 |
| After Hours FMJ Ltd | Health & social care | 2018 |
| AG Khalsa Ltd | Construction | 2021 |
| Agam Enterprise Ltd | Administrative & support | 2007 |
| Agarwood Homes Ltd | Real estate | 2025 |
| Agarwood Property Retail Ltd | Extraterritorial | 2015 |
| Agcpdirect.Com Limited | Wholesale & retail | 2010 |
| Agenda Recruitment Limited | Administrative & support | 2003 |
| Agha Fabrics Ltd | Wholesale & retail | 2025 |
| Agham Ltd | Real estate | 2024 |
| Agim Chiro Limited | Health & social care | 2024 |
| Agostinho Estates Ltd | Real estate | 2024 |
| Agri Plant Hire Limited | Professional & scientific | 2005 |
| AHF Solutions Ltd | Information & communication | 2023 |
| Ahmad Shop Ltd | Wholesale & retail | 2025 |
| Ahmad Traders Limited | Wholesale & retail | 2026 |
| Ahsan ALI Retail Ltd | Wholesale & retail | 2025 |
| Ahype Limited | Wholesale & retail | 2026 |
| AI Optometry Limited | Health & social care | 2024 |
| AI Software Ltd | Information & communication | 2022 |
| AI1984 Limited | Information & communication | 2025 |
| Aicomin Ltd | Information & communication | 2025 |
| Aidagumini Ltd | Professional & scientific | 2025 |
| Aidata Informatics Corporate UK Ltd | Wholesale & retail | 2025 |
| Aidcare Limited | | 1976 |
| AIK Glass Co. Limited | Construction | 2006 |
| Aima Waqar Ltd | Wholesale & retail | 2025 |
| Aimarail Limited | Construction | 2024 |
| Aims IT Ltd | Information & communication | 2014 |
| Aims Technologies Limited | Administrative & support | 2025 |
| Aintree Carpentry Limited | Construction | 2007 |
| Air Care Products Limited | Manufacturing | 1991 |
| Air Exec Limited | Transport & logistics | 1994 |
| Air Tightness Assessors Limited | Construction | 2006 |
| Air Ventilations Limited | Administrative & support | 2002 |
| Airbest Limited | | 1978 |
| Aircycle Ltd | Households | 2025 |
| Airdrome Cars Ltd | Wholesale & retail | 2002 |
| Airfares Direct Ltd | Administrative & support | 1989 |
| Airtec (UK) Ltd | Construction | 2003 |
| AJ Sphere Limited | Other services | 2017 |
| AJ Wraps Limited | Hospitality | 2023 |
| AJB Accounting Services Limited | Professional & scientific | 2002 |
| AJC Consulting & Interim Management Limited | Professional & scientific | 2005 |
| AJC Global Solutions Ltd | Information & communication | 2005 |
| AJC Group Ltd | Professional & scientific | 2024 |
| Ajer Limited | Wholesale & retail | 2021 |
| Ajer Properties Limited | Real estate | 2024 |
| Ajit Contractors Ltd | Construction | 2022 |
| Ajmam Trading Ltd | Wholesale & retail | 2026 |
| AJW GAS Services Limited | Construction | 2007 |
| Ajyal Global Limited | Wholesale & retail | 2026 |
| AK Operator Ltd | Administrative & support | 2016 |
| AK Properties Management Limited | Real estate | 2014 |
| AK World Ltd | Wholesale & retail | 2025 |
| AKA Property Homes Limited | Real estate | 2020 |