| A.M.S. (Southeast) Limited | Construction | 2011 |
| A.N.S Imports Limited | Wholesale & retail | 2025 |
| A101 Solutions (London) Limited | Manufacturing | 2008 |
| A2 Medical Services Ltd | Health & social care | 2024 |
| A3R Logistics Ltd | Wholesale & retail | 2021 |
| A3SL Limited | Professional & scientific | 2014 |
| AA Safety Group Ltd | Administrative & support | 2023 |
| AA Safety Solutions Ltd | Professional & scientific | 2019 |
| Aaleigha’S Limited | Hospitality | 2024 |
| Aarandale Lodge Limited | Health & social care | 2016 |
| AB Estates Holdings Limited | Real estate | 2018 |
| AB Flooring & SON Limited | Construction | 2007 |
| Abbacove Limited | Construction | 1992 |
| Abbot's Hill Limited | Education | 1956 |
| Abbott FM Limited | Construction | 2018 |
| Abc(Essex) Medical Ltd | Health & social care | 2016 |
| Abell Contracts Limited | Construction | 2020 |
| Abery Trade Services Ltd | Construction | 2017 |
| Above & Beyond Extensions & Renovations Limited | Construction | 2023 |
| Abraham Accords Prosperity Group Limited | Financial services | 2025 |
| Abrivia Ltd | Arts & recreation | 2018 |
| Absolute Alarms and Security Systems Limited | Administrative & support | 1996 |
| AC Electrical Essex Ltd | Construction | 2020 |
| Acacia Lodge Care Home Limited | Health & social care | 2021 |
| Acacia Lodge Limited | Health & social care | 2021 |
| Academy Estate Consultants Ltd | Professional & scientific | 2019 |
| Academy Financial Services Limited | Financial services | 2010 |
| Academy Soccer Limited | Arts & recreation | 2006 |
| Acaria Coaching & Consulting Ltd | Professional & scientific | 2019 |
| ACB Building & Maintenance Limited | Construction | 2024 |
| Access ALL Cleaning Ltd | Administrative & support | 2020 |
| Access Green Limited | Financial services | 2015 |
| Access Station Limited | Construction | 2017 |
| Acclaim Building Solutions Ltd | Construction | 2014 |
| Accounting I.T. Limited | Professional & scientific | 1998 |
| Ace Acquisition Company Limited | Administrative & support | 2007 |
| Ace Contracts (London) Holdings Ltd | Other services | 2024 |
| Ace Contracts (London) Limited | Manufacturing | 2000 |
| Ace Fabricators Limited | Manufacturing | 2004 |
| Ace Fire Group Limited | Public administration | 2002 |
| Ace Fire Protection Limited | Public administration | 1995 |
| Ace Services (Enfield) Limited | Construction | 2018 |
| Ace Taxis (Basildon) Limited | Transport & logistics | 2016 |
| Ace Vehicle Repairs Limited | Wholesale & retail | 2013 |
| Acelux Limited | Construction | 2010 |
| Acorn Window and Conservatories Limited | | 1990 |
| Acreage Property Services Limited | Real estate | 2005 |
| Acroflight Ltd | Transport & logistics | 2018 |
| ACS Cambridge Limited | Construction | 2023 |
| ACS Essex Ltd | Construction | 2023 |
| Action Designs Ltd | Information & communication | 2017 |
| Actionbrook Services Limited | Construction | 1997 |
| Active 8 Services Ltd | Information & communication | 2018 |
| Active Body Clinic Ltd | Other services | 2013 |
| Acumen Motorsport Consulting Ltd | Professional & scientific | 2026 |
| AD Money Media Ltd | Professional & scientific | 2025 |
| Adam Global Limited | Financial services | 2012 |
| Adam Global Network Limited | Administrative & support | 2026 |
| Adam Norris Dental Laboratory Limited | Health & social care | 2009 |
| Adamac Plastering Ltd | Construction | 2022 |
| Adastra Financial Ltd | Professional & scientific | 2024 |
| Additional Spaces Limited | Construction | 2020 |
| Adiel Services Ltd | Financial services | 2024 |
| Adigheo Consulting Ltd | Information & communication | 2026 |
| ADM Flooring Limited | Construction | 2007 |
| Admin Pro Limited | Administrative & support | 2025 |
| Adphare Limited | Information & communication | 2023 |
| Advance Plumbing Services Limited | Construction | 2020 |
| Advanced Taxation Solutions Limited | Administrative & support | 2019 |
| Advantaiso Limited | Information & communication | 2023 |
| AF Curcio Limited | Construction | 2015 |
| AF Kimia Limited | Health & social care | 2023 |
| AG Houses Limited | Real estate | 2025 |
| AG OIL Ltd | Mining & quarrying | 2021 |
| Aggb Mort Ltd | Financial services | 2023 |
| AGI Contracts Limited | Construction | 2003 |
| Agilion Insurance Brokers Limited | Extraterritorial | 2024 |
| Agility Physio Rehab Services Ltd | Real estate | 2023 |
| AGL Cars Limited | Wholesale & retail | 2014 |
| AGL Thetford Limited | Real estate | 2021 |
| AGP Coating Ltd | Construction | 2016 |
| Agrimec Sales & Services Limited | Wholesale & retail | 2002 |
| AGS Global Ltd. | Information & communication | 2000 |
| AH Industrial Services Europe Ltd | Professional & scientific | 2020 |
| AHC International Payments Consultancy Ltd | Professional & scientific | 2021 |
| AHJ Property Services Limited | Health & social care | 2016 |
| AIG Engineering Solutions Ltd | Professional & scientific | 2025 |
| Air Property Management Ltd | Households | 2023 |
| Air's Thai Massage Limited | Other services | 2025 |
| Airs Thai Kitchen Ltd | Hospitality | 2025 |
| Ajayi Solutions Limited | Information & communication | 1998 |
| AJB Digital Ltd | Information & communication | 2026 |
| Ajes Properties Ltd | Real estate | 2025 |
| Ajgm Financial Ltd | Financial services | 2023 |
| AJL Construction Management Limited | Real estate | 2015 |
| AJR Electrical Contractors Limited | Construction | 2019 |
| AJW Enterprises (UK) Ltd | Professional & scientific | 2011 |
| AKH Electrical Ltd | Construction | 2026 |
| AKS Wines Ltd | Wholesale & retail | 2024 |
| Akventures Brentwood Ltd | Health & social care | 2024 |