| Absolute Water Tech Solutions Limited | Manufacturing | 2021 |
| Absolutely Green Limited | Construction | 2009 |
| Absolutely Property Limited | Real estate | 2022 |
| AC Independent Social Care Ltd. | Health & social care | 2020 |
| Academy Central (Trinity) RTM Company Ltd | Households | 2016 |
| Accelerateai Ltd | Information & communication | 2023 |
| Access Homelifts Limited | Manufacturing | 2016 |
| Accession Homes Limited | Construction | 2002 |
| Accountancy Practice Assistant Limited | Administrative & support | 2022 |
| Ace Medical Services Limited | Health & social care | 2016 |
| Acesellers Limited | Wholesale & retail | 2019 |
| ACG Rail Limited | Construction | 2014 |
| Achill Properties Limited | Real estate | 2010 |
| ACN Academy UK Ltd | Education | 2024 |
| Acra Payroll Services Ltd | Administrative & support | 2023 |
| Acrail Ltd | Construction | 2023 |
| ACS Window Cleaning Limited | Administrative & support | 2021 |
| Activate Educate Ltd | Administrative & support | 2026 |
| Active Journeys CIC | Education | 2026 |
| Active Life for a Healthier YOU CIC | Health & social care | 2011 |
| Active Training and Management Ltd | Health & social care | 2019 |
| Acumen Essex Ltd | Real estate | 2024 |
| Adalia Market Ltd | Professional & scientific | 2014 |
| Adam Hall Ltd. | Wholesale & retail | 1978 |
| Addiction Lifeline Ltd | Public administration | 2021 |
| Adelis Logistics Ltd | Transport & logistics | 2021 |
| Adgold Consultancy Limited | Professional & scientific | 2014 |
| Adherepro Ltd | Professional & scientific | 2025 |
| ADHPLUMBINGANDHEATING1 Ltd | Construction | 2024 |
| Admiral Court RTM Company Limited | Households | 2011 |
| Adon Holdings Ltd | Real estate | 2016 |
| Adonaya Care Services Ltd | Health & social care | 2025 |
| Adrian & Sophie Ltd | Hospitality | 2021 |
| Adrian Eves Joinery Ltd | Construction | 2015 |
| ADS Groundworks Ltd | Construction | 2009 |
| Advance Auto Centre Limited | Wholesale & retail | 1997 |
| Advance Health Limited | Health & social care | 2026 |
| Advanced Building Facilities Limited | Construction | 2007 |
| Advanced Engineering Support Services Ltd | Construction | 2004 |
| Advanced Exchanges Ltd | Wholesale & retail | 2023 |
| Advanced Project Concepts Ltd | Professional & scientific | 2025 |
| Advanced Tech Limited | Construction | 2011 |
| Advantage 999 Limited | Wholesale & retail | 2001 |
| AED Real Estate Ltd | Real estate | 2022 |
| Aeon Sourcing Limited | Real estate | 2025 |
| AEP Cleaning Services Limited | Extraterritorial | 2019 |
| Aero Partners Limited | Transport & logistics | 2000 |
| Aerotech Aircraft Services Ltd | Manufacturing | 2026 |
| Aesthetics by Siobhan Ltd | Other services | 2025 |
| Aethus Limited | Information & communication | 2026 |
| Aevora Limited | Health & social care | 2026 |
| Af&O Limited | Hospitality | 2014 |
| AFC Consultants Ltd | Information & communication | 2022 |
| Agata Orthodontic Therapist Limited | Health & social care | 2015 |
| Agile Connect Ltd | Information & communication | 2019 |
| Agile Test Solutions Ltd | Information & communication | 2015 |
| Agir Foods Ltd | Hospitality | 2026 |
| AGL Ceramics Ltd | Construction | 2021 |
| AGL International Group Ltd | Wholesale & retail | 2020 |
| Aglio, Olio E Peperoncino Ltd | Information & communication | 2025 |
| Agmi Properties Ltd | Real estate | 2024 |
| Agorium Ltd | Wholesale & retail | 2017 |
| AGR Trading & Services Ltd | Wholesale & retail | 2019 |
| Agrious Surveyors Limited | Professional & scientific | 2026 |
| AGS Hampshire Holdings Ltd | Financial services | 2022 |
| AGS People and Recruitment Ltd | Health & social care | 2022 |
| AGW Mortgage Brokers Limited | Financial services | 2015 |
| Ahmed Brothers Enterprises Ltd | Wholesale & retail | 2015 |
| AI Alchemy Ltd | Information & communication | 2025 |
| AI Business Support Ltd | Information & communication | 2025 |
| Aifa's Restaurant Exeter Ltd | Hospitality | 2025 |
| Aigt Limited | Information & communication | 2017 |
| Aila Ilana & Co Limited | Wholesale & retail | 2025 |
| Aims Education Limited | Education | 2021 |
| AIP 24X7 Ltd | Information & communication | 2021 |
| Air Falcon Limited | Transport & logistics | 2008 |
| Airborne Industries Limited | Extraterritorial | 2007 |
| Airborne Operations Limited | Professional & scientific | 2002 |
| Aircraft Component Services (2002) Limited | Professional & scientific | 2002 |
| Aircraft Component Services Limited | Wholesale & retail | 2002 |
| Aircraft Component Spares Ltd | Wholesale & retail | 2024 |
| Airrite Services Limited | Manufacturing | 2025 |
| Airsyne Limited | Information & communication | 2026 |
| Aitrion Ltd | Information & communication | 2026 |
| Aiuta Health Ltd | Health & social care | 2025 |
| AJ Wood Tech Ltd | Professional & scientific | 2025 |
| Ajaa Properties Limited | Real estate | 2024 |
| AJB Plumbing & Heating ( Essex) Limited | Construction | 2018 |
| AJH Building Design Limited | Construction | 2026 |
| Ajiish & Co Limited | Wholesale & retail | 2021 |
| Ajjw Group Ltd | Real estate | 2026 |
| AJM Building Solutions Ltd | Construction | 2015 |
| AJM IT Services Limited | Information & communication | 2015 |
| AJM Recruitment Ltd | Administrative & support | 2022 |
| AJR Eco (Group) Ltd | Financial services | 2023 |
| AJR Eco (Properties) Ltd | Real estate | 2023 |
| AJR Eco Ltd | Construction | 2001 |
| AJT Executive Search Limited | Administrative & support | 2016 |
| Akach Properties Ltd | Extraterritorial | 2024 |
| AKD Horizon Limited | Wholesale & retail | 2026 |