| Apnea-Tech Limited | Manufacturing | 2020 |
| APO Stores Limited | Wholesale & retail | 2018 |
| Apollo ONI Ltd | Health & social care | 2023 |
| Apollo Trade Limited | Information & communication | 1999 |
| App Code Limited | Information & communication | 2011 |
| Appelle Consultants Limited | Administrative & support | 2011 |
| Appla Ltd | Education | 2017 |
| Apple Vending & Catering Services Limited | Administrative & support | 2009 |
| Applecross Property Co Ltd | Construction | 2024 |
| Applecross Safety Assessments Limited | Professional & scientific | 2008 |
| Applejacks Farm Ltd | Professional & scientific | 2018 |
| Applepark Limited | Information & communication | 2004 |
| Apples & Oranges Data Solutions Ltd | Administrative & support | 2013 |
| Appleton Accounting Limited | Professional & scientific | 2008 |
| Appleton Agencies Limited | Wholesale & retail | 2024 |
| Appleton Builders Limited | Construction | 2019 |
| Appleton Electrics Ltd | Construction | 2020 |
| Appleton Engineering Services Limited | Professional & scientific | 2022 |
| Appleton Hall Veterinary Clinic Limited | Professional & scientific | 2013 |
| Appleton Harvey Ltd | Real estate | 2023 |
| Appleton Print Ltd | Manufacturing | 2021 |
| Appleton Rifle Club Limited | Arts & recreation | 1964 |
| Appleton Utility Consultancy Ltd | Administrative & support | 2009 |
| Applied Computing Limited | Professional & scientific | 2011 |
| Applied Engineering Consultants Limited | Information & communication | 2019 |
| Applied Focus Marketing Solutions Limited | Administrative & support | 2016 |
| Applied Machinery Limited | Administrative & support | 2013 |
| Applied Metrology Solutions Ltd | Professional & scientific | 2026 |
| Appraisd Ltd | Information & communication | 2004 |
| Approved Installation Specialists Limited | Transport & logistics | 2013 |
| Approvol Limited | Information & communication | 2019 |
| Appserve Ltd | Professional & scientific | 2025 |
| Appspec Limited | Administrative & support | 2015 |
| Appsserve Solution Limited | Information & communication | 2014 |
| APR Payroll Limited | Administrative & support | 2023 |
| Apres Life Limited | Wholesale & retail | 2022 |
| Apricus Limited | Administrative & support | 2024 |
| APT Social Care Ltd | Health & social care | 2022 |
| APT Squirrel Designs Ltd | Professional & scientific | 2024 |
| APX Consulting Ltd | Professional & scientific | 2019 |
| AQ Engineering Services Limited | Professional & scientific | 2018 |
| Aq-Tec Limited | Wholesale & retail | 2023 |
| Aqua-Pro Engineering Ltd | Professional & scientific | 2020 |
| Aquacut Limited | Manufacturing | 1998 |
| Aquaheat Heating Ltd | Construction | 2025 |
| Aquaheat Heating Services Limited | Construction | 2019 |
| Aquaprintuk Limited | Manufacturing | 2021 |
| Aquatec Contracts Limited | Financial services | 1999 |
| Aquila Defence Consultancy Ltd | Professional & scientific | 2019 |
| Aquila Heating and Plumbing Ltd | Construction | 2012 |
| Aquila Medical Services Limited | Health & social care | 2015 |
| AR Electrical & Building Services Ltd | Administrative & support | 2023 |
| AR Livingstone Ltd | Real estate | 2022 |
| AR Mcardle Consulting Limited | Professional & scientific | 2024 |
| Araceli Lopes Ltd | Information & communication | 2024 |
| Aran Engineering Limited | Administrative & support | 2012 |
| Arapeerally Limited | Administrative & support | 2023 |
| Arase Consult Ltd | Professional & scientific | 2017 |
| Arbitrium Associates Limited | Administrative & support | 2024 |
| Arbitrium Consultancy Ltd | Administrative & support | 2020 |
| Arboriculture 1 Limited | Other services | 2017 |
| ARC Window Films Ltd | Construction | 2011 |
| Arc-A Engineering Solutions Limited | Administrative & support | 2011 |
| Arcade Office Refurbishments Ltd | Construction | 2006 |
| Arcane Consultancy Ltd | Other services | 2019 |
| Arch Construction Limited | Construction | 1988 |
| Arch Electrical Installations Limited | Construction | 2016 |
| Archer Engineering Solutions Ltd | Administrative & support | 2025 |
| Archer Projects Limited | Construction | 2024 |
| Archibliss Limited | Information & communication | 2018 |
| Archie RAO Consulting Ltd | Health & social care | 2019 |
| Archipode Limited | Arts & recreation | 2016 |
| Archyoung Ltd | Wholesale & retail | 2013 |
| Arclight Engineering Services Ltd | Other services | 2018 |
| Arclin UK Holdings Limited | Manufacturing | 2025 |
| Arcon Construction Supplies Ltd | Wholesale & retail | 2018 |
| ARD Consultancy Services Ltd | Professional & scientific | 2024 |
| Arden Rede Limited | Information & communication | 2025 |
| Ardis Ltd | Health & social care | 2019 |
| Ardoch Engineering Limited | Professional & scientific | 2020 |
| Arena Housing Group Pension Trustees Limited | Financial services | 1997 |
| Arena Learning Limited | Administrative & support | 2022 |
| Arendelle Consultants Limited | Professional & scientific | 2014 |
| Ares&Zeyn Construction Limited | Construction | 2026 |
| Arete Synthetic Limited | Arts & recreation | 1994 |
| ARF Van Sales Limited | Wholesale & retail | 2013 |
| Arfreight Ltd | Transport & logistics | 2018 |
| ARG Projects Ltd | Real estate | 2021 |
| Argent Air Conditioning Limited | Construction | 2023 |
| Argent Consultant Ltd | Professional & scientific | 2022 |
| Argus Capital Ltd | Other services | 2015 |
| ARH Design Engineering Ltd | Professional & scientific | 2019 |
| ARH Property Management Limited | Real estate | 2024 |
| Arial AI Ltd | Information & communication | 2025 |
| Ariarch Limited | Other services | 2017 |
| Aries Cleans Limited | Administrative & support | 2026 |
| Aries Marquee Hire Ltd | Administrative & support | 2024 |
| Arikos Limited | Professional & scientific | 2019 |
| ARK Aerotek Ltd | Administrative & support | 2021 |
| ARK Luxury Limited | Wholesale & retail | 2025 |