| Arbis Consulting Ltd | Professional & scientific | 2022 |
| Arbonne Group Ltd | Administrative & support | 2019 |
| Arbor Creative Ltd | Information & communication | 2023 |
| Arbora Homes (Braiswick) Limited | Construction | 2018 |
| Arbora Homes (Castle Camps) Limited | Construction | 2018 |
| Arbora Homes (Fordham) Limited | Construction | 2018 |
| Arbora Homes (Gosfield) Limited | Construction | 2022 |
| Arbora Homes (Harpers Hill 2) Limited | Construction | 2018 |
| Arbora Homes (Harpers Hill) Limited | Construction | 2018 |
| Arbora Homes (Westleton) Limited | Construction | 2022 |
| Arbora Homes Limited | Construction | 2015 |
| Arbora Rent (Nayland) Limited | Real estate | 2023 |
| Arbora Rent Limited | Real estate | 2021 |
| ARC Alignment Ltd | Professional & scientific | 2026 |
| ARC Express Ltd | Transport & logistics | 2011 |
| ARC Legal Assistance Limited | Financial services | 2003 |
| ARC of Life Limited | Real estate | 2018 |
| Arcad Ltd | Professional & scientific | 2026 |
| Arcadia IT Solutions Ltd | Information & communication | 2023 |
| Arcadia JEJ Ltd | Public administration | 2020 |
| Arcaria Financial Solutions Ltd | Financial services | 2012 |
| Arcem.Io Limited | Information & communication | 2020 |
| Archer Carpentry & Renovations Ltd | Manufacturing | 2022 |
| Archer Carpentry Ltd | Construction | 2018 |
| Archer Distribution Limited | Wholesale & retail | 2013 |
| Archer Property Limited | Real estate | 2018 |
| Archer Windows Holdings Limited | Financial services | 2024 |
| Archers Court (South Ockendon) Management Company Limited | Households | 1991 |
| Archies Forge Limited | Professional & scientific | 2021 |
| Archimedes Software Consultants Limited | Information & communication | 1995 |
| Architectura Ltd | Construction | 2025 |
| Architectural Steel Fabrications Ltd | Manufacturing | 2011 |
| Architecture One Suffolk Ltd | Professional & scientific | 2025 |
| Archor LLP | | 2020 |
| Arcos Structures Limited | Professional & scientific | 2008 |
| Arcyon Ltd | Health & social care | 2020 |
| Ardc (UK) Limited | Financial services | 2013 |
| Ardeca Limited | Real estate | 2025 |
| Ardleigh Building Supplies Limited | Wholesale & retail | 2020 |
| Ardleigh Court Residents' Association Limited | Real estate | 1974 |
| Ardleigh Garage Services Ltd | Wholesale & retail | 2014 |
| Ardleigh Limited | Administrative & support | 2007 |
| Ardleigh Sands Limited | Professional & scientific | 2009 |
| ARG Catering Solutions Ltd | Hospitality | 2024 |
| Argent Berry Group Limited | Administrative & support | 2015 |
| Argent By-Products Group Limited | Extraterritorial | 1932 |
| Argent Desserts Limited | Financial services | 2026 |
| Argent Europe Limited | Extraterritorial | 1996 |
| Argent Foods Group Limited | Extraterritorial | 2016 |
| Argent Foods Limited | Professional & scientific | 2009 |
| Argent Group Europe Limited | Professional & scientific | 2006 |
| Argent Holdings Limited | Professional & scientific | 1997 |
| Argent Meat Traders Limited | Manufacturing | 1941 |
| Argent Roofing Limited | Construction | 2022 |
| Argo Mail Ltd | Transport & logistics | 2013 |
| Aria 3D Consulting Ltd | Professional & scientific | 2019 |
| Ariel Patisserie Limited | Manufacturing | 2025 |
| Arinami Ltd | Professional & scientific | 2025 |
| Ario Dog Ltd | Agriculture & fishing | 2025 |
| Arja Ltd | Health & social care | 2019 |
| Arjun Traders Limited | Wholesale & retail | 2017 |
| ARK Homes Builders & Developers Limited | Construction | 2002 |
| ARK Marketing Limited | Professional & scientific | 2010 |
| ARK Roofing & Building Limited | Construction | 2020 |
| Arkham Automotive Ltd | Professional & scientific | 2023 |
| Arlington Investment Management Limited | Financial services | 2007 |
| Arlo Storage (Ilkeston) Ltd | Administrative & support | 2025 |
| Arma Europe Limited | Financial services | 2015 |
| Arma Karma Limited | Financial services | 2019 |
| Armay Accounting Services Ltd | Professional & scientific | 2024 |
| Armeg Plumbing Services Ltd | Construction | 2018 |
| Armis Design Limited | Professional & scientific | 2025 |
| Armoury Autos Limited | Wholesale & retail | 2011 |
| Armtranservices Ltd | Transport & logistics | 2023 |
| ARMZ-2024 Limited | Wholesale & retail | 2024 |
| Arnold Electrical Ltd | Construction | 2015 |
| Arnold Total Flooring Limited | Construction | 2010 |
| Arnold's Designs Ltd | Wholesale & retail | 2021 |
| Arnull's Ltd | Construction | 2024 |
| ARO Electrical Limited | Construction | 2025 |
| Aromak Limited | Hospitality | 2023 |
| ARP Consulting Services Limited | Professional & scientific | 2024 |
| Arrow VAT Limited | Professional & scientific | 2024 |
| Arrowclouds Business Solutions Ltd | Wholesale & retail | 2024 |
| Arsalanz Ltd | Health & social care | 2025 |
| Arslan Associates Limited | Wholesale & retail | 2025 |
| Arteq Design Consultants Ltd | Professional & scientific | 2012 |
| Arteseal Ltd | Wholesale & retail | 2023 |
| Arthouse Direct Holdings Ltd | Extraterritorial | 2015 |
| Arthur Cock and Sons Limited | Wholesale & retail | 2002 |
| Artisaine Limited | Health & social care | 2012 |
| Artizan Global Ltd | Professional & scientific | 2020 |
| Artizart C.I.C. | Education | 2026 |
| Artless Wealth Ltd | Financial services | 2020 |
| Arts Capital Limited | Professional & scientific | 2021 |
| Artsy Image Limited | Professional & scientific | 2017 |
| Artura Holdings Ltd | Financial services | 2025 |
| Artura Tech Solutions Ltd | Information & communication | 2025 |
| Arulampalam Services Limited | Health & social care | 2008 |
| ARV Services Ltd | Manufacturing | 2016 |