| Ashby Brooks LLP | | 2025 |
| Ashby Moving Group Limited | Transport & logistics | 2017 |
| Ashcroft Housing Ltd | Real estate | 2020 |
| Ashcroft Safe Housing Community Interest Company | Hospitality | 2025 |
| Ashfield Way Management Limited | Households | 1971 |
| Ashford Conway Ltd | Administrative & support | 2025 |
| Ashish & Rebecca Rama Ltd | Professional & scientific | 2020 |
| Ashki Ltd | Professional & scientific | 2017 |
| Ashlans Limited | Real estate | 2017 |
| Ashley & Harry Blinds Limited | Manufacturing | 2021 |
| Ashmead Applications Limited | Information & communication | 1992 |
| Ashmond Engraving Limited | Manufacturing | 1986 |
| Ashmond Limited | Extraterritorial | 2009 |
| Ashpark Properties Limited | Construction | 2012 |
| Ashton Park Limited | Agriculture & fishing | 2000 |
| Ashton's Build Limited | Construction | 2025 |
| Ashtons Heating Limited | Construction | 2024 |
| Ashtree House Limited | Health & social care | 2011 |
| Ashwin & Thaya Limited | Health & social care | 2024 |
| Ashwood Construction Solutions Limited | Construction | 2017 |
| Ashwood Group Limited | Hospitality | 2022 |
| Ashwood Heating Ltd | Construction | 2019 |
| Ashwood SIX RTM Limited | Households | 2008 |
| Ashwood Travel Limited | Transport & logistics | 2010 |
| ASI Traders Limited | Wholesale & retail | 2022 |
| ASJ Operations Ltd | Construction | 2022 |
| ASK Accountants HW Ltd | Professional & scientific | 2012 |
| ASK Accounts and Tax Services Limited | Professional & scientific | 2023 |
| ASK Hub Ltd | Wholesale & retail | 2025 |
| ASL Petrophysics Ltd | Professional & scientific | 2020 |
| ASN Wholesale Ltd | Wholesale & retail | 2025 |
| ASP Electrical Services Ltd | Construction | 2021 |
| Aspect Safety Performance Consulting Ltd | Professional & scientific | 2015 |
| Aspectridge Properties Limited | Real estate | 2021 |
| Aspects Home Improvements Ltd | Construction | 2021 |
| Aspeer Holdings Limited | Information & communication | 2007 |
| Aspeer Media Limited | Information & communication | 2007 |
| Aspen Stone Limited | Households | 2026 |
| Aspirar Ltd | Construction | 2011 |
| Aspirational Financial Planning Limited | Financial services | 2020 |
| Aspire Cars Beaconsfield Limited | Transport & logistics | 2024 |
| Aspire Cars G/X Limited | Transport & logistics | 2022 |
| Aspire Executive Limited | Transport & logistics | 2011 |
| Aspire for Young People | Education | 2020 |
| Aspire Pathway Support and Accommodation Ltd | Administrative & support | 2026 |
| Aspire Schools | Education | 2016 |
| Aspiring Classics Ltd | Wholesale & retail | 2020 |
| Aspiring Handz Ltd | Education | 2025 |
| Aspium Limited | Professional & scientific | 2019 |
| ASR Commercials Ltd | Wholesale & retail | 2021 |
| ASR Couriers Ltd | Transport & logistics | 2025 |
| Assembly Guys Ltd | Manufacturing | 2023 |
| Asset Logic Systems Ltd | Information & communication | 2024 |
| Asset Ltd | Wholesale & retail | 2003 |
| Asset Property Partners Limited | Real estate | 2023 |
| Assetbanc Ltd | Professional & scientific | 2006 |
| Assured Quality Care Ltd | Hospitality | 2025 |
| Assuriant Consulting Ltd | Information & communication | 2016 |
| Astintom Property Limited | Real estate | 2020 |
| Astir Super Commercial Cleaning Service Ltd | Administrative & support | 2024 |
| Astles Holdings Limited | Real estate | 2021 |
| Aston Algora Limited | Wholesale & retail | 2026 |
| Aston Gray Limited | Real estate | 2020 |
| Astral AU Pairs Ltd | Other services | 2008 |
| Astricus Ltd | Professional & scientific | 2023 |
| Astute CEE Limited | Education | 2016 |
| Astute Consulting Solutions Limited | Information & communication | 2015 |
| ASW Media Ltd | Professional & scientific | 2020 |
| ASW Repairs Limited | Wholesale & retail | 2014 |
| AT & M Brothers Limited | Wholesale & retail | 2021 |
| AT Engineering Consultancy Limited | Professional & scientific | 2018 |
| AT Ground Level Limited | Construction | 2011 |
| AT Home IT Ltd | Other services | 2002 |
| AT the Woodalls Limited | Professional & scientific | 2022 |
| Ataihq Ltd | Information & communication | 2026 |
| ATE Enterprises Ltd | Information & communication | 2015 |
| Atelier House UK Limited | Manufacturing | 2023 |
| Atenso Limited | Extraterritorial | 2019 |
| Athena Stonecare Limited | Administrative & support | 2012 |
| Atherville Management Company Limited | Households | 1964 |
| Athlete Service Limited | Wholesale & retail | 2012 |
| Atiframai Limited | Manufacturing | 2011 |
| Atlas Contractors London Ltd | Construction | 2021 |
| Atlas Global Trade Limited | Wholesale & retail | 2026 |
| Atlas Landscaping and Property Services Limited | Administrative & support | 2021 |
| Atlas Plumbers Electrical & Plumbing Ltd | Construction | 2019 |
| Atlas Studios Group Ltd | Information & communication | 2026 |
| ATO Lettings Ltd | Real estate | 2025 |
| Atom Property Services Ltd | Construction | 2018 |
| ATS Mechanical Services Limited | Energy | 2014 |
| Atsas Creation International Ltd | Wholesale & retail | 2023 |
| Attractmore Limited | Information & communication | 2015 |
| Atula Technologies Limited | Information & communication | 2020 |
| Atzs Technology Ltd | Professional & scientific | 2020 |
| Audio Vision London Ltd | Construction | 2020 |
| Audio Visual Facilities Maintenance Ltd | Manufacturing | 2011 |
| Auditel Rental and Service Limited | Manufacturing | 2008 |
| Auditel Systems Integration Limited | Manufacturing | 2011 |
| Auditel Systems Limited | Manufacturing | 2018 |
| Audny Ltd | Health & social care | 2018 |