| Agile DEV Ltd | Information & communication | 2024 |
| AGJ Property Ltd | Real estate | 2026 |
| Agri Partnership Asset Management Ltd | Administrative & support | 2016 |
| Agricore Solutions Limited | Agriculture & fishing | 2026 |
| Ahaux Holdings Limited | Financial services | 2024 |
| AHP Limited | Administrative & support | 2017 |
| AHP Photo Limited | Administrative & support | 2018 |
| AI Digital Solutions Limited | Information & communication | 2025 |
| AI Partners Limited | Information & communication | 2011 |
| AI Systems Consulting Ltd | Information & communication | 2025 |
| AIA Homes LLP | | 2017 |
| AIA Investment Limited | Real estate | 2017 |
| Aice Architecture Limited | Professional & scientific | 2008 |
| Aide Consultancy Limited | Information & communication | 2018 |
| Aiden Spackman Limited | Administrative & support | 2008 |
| Aikaja Investment Limited | Real estate | 2013 |
| Aikaja LLP | | 2013 |
| Aim-Straight Limited | Manufacturing | 2007 |
| Air Charter Miner Ltd. | Transport & logistics | 2015 |
| Air Corps Air Conditioning Ltd | Energy | 2022 |
| Air Crew Accommodation Ltd | Hospitality | 2019 |
| Aira Psychology Limited | Health & social care | 2017 |
| Airaphon Ltd | Information & communication | 2020 |
| Airblade Software Limited | Information & communication | 2006 |
| Airsonett UK Limited | Administrative & support | 2008 |
| AJ Chef Limited | Hospitality | 2026 |
| AJ DEL Mundo Ltd. | Health & social care | 2015 |
| Aj's Rustic Cafe Ltd | Hospitality | 2025 |
| Ajax Property Services Ltd | Real estate | 2024 |
| AJB Forecasting Systems Limited | Information & communication | 2015 |
| AJB Strategies Limited | Professional & scientific | 2012 |
| AJG Hospitality Limited | Hospitality | 2014 |
| AJH Advisory Ltd | Financial services | 2022 |
| AJM Consultants (UK) LLP | | 2013 |
| Akhil Tech Limited | Information & communication | 2019 |
| AKR Advisory Group Ltd | Information & communication | 2024 |
| Akwaaba Care Services Kent Limited | Administrative & support | 2018 |
| AL Amanah Group Limited | Hospitality | 2024 |
| Al-Buraq-Khan Ltd | Wholesale & retail | 2025 |
| Al-Thukair Limited | Administrative & support | 2019 |
| Alan Auld Flooring Ltd | Wholesale & retail | 2006 |
| Alan Pink Tax Offices LLP | | 2011 |
| Albarmatt Property Ltd | Real estate | 2021 |
| ALCH3MIST Limited | Administrative & support | 2008 |
| Alchemica Ltd | Manufacturing | 2025 |
| Aldea Trans 2019 Ltd | Transport & logistics | 2019 |
| Alecom Europe Ltd | Transport & logistics | 2020 |
| Aledo K9 Ltd | Other services | 2022 |
| Alex Pocock Lighting Limited | Wholesale & retail | 2011 |
| Alexander Bates Campbell Europe Limited | Financial services | 2023 |
| Alexander Bates Campbell Financial Planning Limited | Administrative & support | 2010 |
| Alexander Bates Campbell Holdings Limited | Financial services | 2021 |
| Alexander Renovations (Kent) Ltd | Construction | 2023 |
| Alexander Williams Recruitment Ltd | Administrative & support | 2022 |
| Alexandre Boyes (Maintenance) Ltd | Households | 2015 |
| Alexandre Boyes (Management) Ltd | Households | 2015 |
| Alexandre Boyes Ltd | Households | 2015 |
| Algen Limited | Administrative & support | 1985 |
| Algn Studio Ltd | Arts & recreation | 2026 |
| Algx Advisory Ltd | Professional & scientific | 2026 |
| ALH Wells Properties Ltd | Real estate | 2025 |
| Alhstede Limited | Real estate | 2021 |
| Alice Dyke Ltd | Professional & scientific | 2025 |
| Alicorn Equestrian Ltd | Wholesale & retail | 2017 |
| Alinety Ltd | Information & communication | 2025 |
| Alis Richardson Fitness Ltd | Arts & recreation | 2022 |
| Alite Tech Ltd | Wholesale & retail | 2022 |
| Alivein Tech Limited | Information & communication | 2017 |
| ALL About Building Services Ltd | Construction | 2020 |
| ALL CNC Ltd | Manufacturing | 2024 |
| ALL Fortune Limited | Hospitality | 2021 |
| ALL Road Solutions Ltd | Transport & logistics | 2024 |
| ALL Saints Consultancy Ltd | Professional & scientific | 2022 |
| ALL the Arts Theatre School Limited | Arts & recreation | 2009 |
| All-In Media Ltd | Information & communication | 2025 |
| Allen Applied Ltd | Education | 2026 |
| Allen Scott Limited | Professional & scientific | 2005 |
| Allez Limited | Construction | 1999 |
| Allkin Group Limited | Manufacturing | 2022 |
| Allport Investments York Ltd | Real estate | 2013 |
| Allport Properties York Ltd | Construction | 2014 |
| Alltap Limited | Wholesale & retail | 2023 |
| Allumno Limited | Professional & scientific | 2016 |
| Almax Advisory Limited | Construction | 2026 |
| Alpera Limited | Information & communication | 2016 |
| Alpha Cabs Ltd | Transport & logistics | 2024 |
| Alphapig Investments LLP | | 2020 |
| Alpheus Living (UK) Ltd | Real estate | 2019 |
| Alpheus Property Ltd | Real estate | 2018 |
| Alpine Actuarial Consulting Ltd | Professional & scientific | 2026 |
| Alsot Limited | Financial services | 2003 |
| ALT Nexus Ltd | Professional & scientific | 2025 |
| ALT Scale Ltd | Information & communication | 2020 |
| Alternative Asset Strategies LLP | | 2012 |
| Altimus Consulting Ltd | Professional & scientific | 2023 |
| Altion Engineering Limited | Manufacturing | 2022 |
| Altitude Works Ltd | Information & communication | 2025 |
| Altuccia Limited | Information & communication | 2024 |
| Alun Marks Limited | Professional & scientific | 2020 |
| ALW Designs Limited | Administrative & support | 2023 |