| ADB Accountancy Limited | Professional & scientific | 2024 |
| Addelam Services Limited | Professional & scientific | 2020 |
| Adenza Solutions Limited | Professional & scientific | 2010 |
| Adisa Certification Limited | Information & communication | 2010 |
| Adisa Group Limited | Information & communication | 2020 |
| Adjusting & Management Solutions (UK) Ltd | Financial services | 2012 |
| ADM Counsel Ltd | Health & social care | 2026 |
| ADP3 Residentials Ltd | Real estate | 2025 |
| Adrian Clarke Associates Ltd | Professional & scientific | 2008 |
| Adrian Hodges Advisory Limited | Professional & scientific | 2012 |
| Advanced Automotive Technologies Limited | Financial services | 2015 |
| Advanced HR Ltd | Professional & scientific | 2025 |
| Advantage Waste and Recycling Ltd | Professional & scientific | 2020 |
| Adventure Tuition Limited | Education | 2014 |
| Advice 1ST Limited | Financial services | 2023 |
| AEP LAB Ltd | Health & social care | 2010 |
| Aequitas Capital Limited | Professional & scientific | 2026 |
| Aero-Biz UK Ltd | Professional & scientific | 2009 |
| Aerowise Services Ltd | Professional & scientific | 2021 |
| AES Equipment Services Ltd | Construction | 2015 |
| Aetha Ltd | Wholesale & retail | 2020 |
| Afridi Consulting Limited | Information & communication | 2025 |
| Afvk Consulting Ltd | Professional & scientific | 2024 |
| Agecourt Limited | Construction | 2023 |
| AGH Capital Ltd | Professional & scientific | 2023 |
| Agile Accounting Ltd | Professional & scientific | 2020 |
| Agile Interactions Ltd | Information & communication | 2017 |
| AGL Construction Services Ltd | Construction | 2015 |
| Agri Corp Limited | Agriculture & fishing | 2006 |
| AGS Real Capital Ltd | Real estate | 2025 |
| Ahmco Heating Supplies Ltd | Wholesale & retail | 2012 |
| Ailisen Limited | Wholesale & retail | 2025 |
| Ailsa ROW Management Company Ltd | Households | 2024 |
| Ainea International Limited | Wholesale & retail | 2018 |
| Aird Motors Limited | Wholesale & retail | 1989 |
| AIV Engineering Ltd | Construction | 2019 |
| Aivilo Property Management Limited | Real estate | 2022 |
| AJ Survey Limited | Real estate | 2008 |
| AJD Music Services Ltd | Information & communication | 2024 |
| AJL Financial Services Ltd | Professional & scientific | 2023 |
| AJS Sports Limited | Arts & recreation | 2023 |
| Akers Holdings Ltd | Information & communication | 2003 |
| AKH Productions Ltd | Information & communication | 2003 |
| Akrill House Limited | Households | 2004 |
| Akwatia LLP | | 2021 |
| Alan J Gardner Glazing Limited | Construction | 2024 |
| Alanowo Ltd | Real estate | 2026 |
| Alban Developments Limited | Construction | 1963 |
| Alban Financial Services Limited | Financial services | 2014 |
| Alban Perrin Limited | Professional & scientific | 2009 |
| Albany Court (Milton Road) Management Limited | Households | 1966 |
| Album Brands Ltd | Professional & scientific | 2023 |
| Alchemy AI Ltd | Information & communication | 2018 |
| Alderington Property Ltd | Real estate | 2020 |
| Aldersheff Limited | Construction | 2018 |
| Alderslade Ltd | Professional & scientific | 2005 |
| Aldwick Advisory Services Limited | Professional & scientific | 2020 |
| Aldwickbury Ltd | Real estate | 2024 |
| Aldwickbury School Trust Limited | Education | 1969 |
| Alemso Limited | Professional & scientific | 2020 |
| Alex Helsby Music Ltd | Information & communication | 2024 |
| Alex Thomas Financial Planning Limited | Professional & scientific | 2018 |
| Alexander Partners Limited | Real estate | 2000 |
| Aleyla Software Ltd | Information & communication | 2021 |
| Alford Consulting Ltd | Professional & scientific | 2019 |
| Algoritmik Limited | Information & communication | 2020 |
| Alina Sandell Consulting Ltd | Administrative & support | 2016 |
| Alinberen Software Solutions and IT Consultancy Ltd | Information & communication | 2021 |
| Allied Cycles Limited | Wholesale & retail | 2011 |
| Alltomation Limited | Construction | 2009 |
| Alpe Wealth Management Limited | Financial services | 2020 |
| Alpha Capital Group Limited | Information & communication | 2021 |
| Alpha Effect Global Limited | Financial services | 2020 |
| Alpha Futures Limited | Information & communication | 2024 |
| Alpha Group UK Holdings Ltd | Financial services | 2026 |
| Alpha Merch Ltd | Wholesale & retail | 2025 |
| Alpha Prime Markets Limited | Education | 2022 |
| Alpha Pulse Ltd | Information & communication | 2025 |
| Alpine Physiotherapy Limited | Extraterritorial | 2017 |
| Alpine Therapy Ltd | Extraterritorial | 2016 |
| Alto AI Limited | Information & communication | 2025 |
| Alukrom Developments Limited | Real estate | 2024 |
| Aluxide Ltd | Wholesale & retail | 2021 |
| Alvallio Ltd | Manufacturing | 2021 |
| Always Off-Peak Limited | Construction | 2025 |
| Always Ready Trading Limited | Wholesale & retail | 2024 |
| Amain Ltd | Wholesale & retail | 2025 |
| Amalgamated Properties Limited | Construction | 1923 |
| Amalis Consulting Ltd | Professional & scientific | 2009 |
| Amba Group One Limited | Professional & scientific | 2022 |
| Amba Group One Property Ltd | Real estate | 2023 |
| Amber REC1 Ltd | Real estate | 2026 |
| Ambers Gold Homes Limited | Real estate | 2001 |
| Ambia Renewables Limited | Other services | 2024 |
| AMD Ceramics Limited | Construction | 2019 |
| Amedev Ltd | Professional & scientific | 2025 |
| Ameleon Ltd | Professional & scientific | 2014 |
| AMEN26 Limited | Professional & scientific | 2026 |
| Amgp Consulting Limited | Information & communication | 2024 |
| Amoship Ltd | Wholesale & retail | 2023 |