| Animal Impact Ltd | Administrative & support | 2018 |
| Animal Ventures Ltd | Administrative & support | 2017 |
| Animashaun Printing Concept Limited | Manufacturing | 2022 |
| Animating Education CIC | Education | 2023 |
| Anitha Mahender Reddy Limited | Wholesale & retail | 2026 |
| Annas Legacy Holdings Ltd | Real estate | 2026 |
| Antenna Industries Limited | Information & communication | 2008 |
| Antica Roma Restaurant Limited | Hospitality | 2012 |
| Anton Smith Academy (ASA) Ltd | Education | 2017 |
| Antonelahazizi Limited | Hospitality | 2026 |
| Antonia Dinca Limited | Wholesale & retail | 2025 |
| Anuki Properties Ltd | Real estate | 2024 |
| ANW Decorations Ltd | Wholesale & retail | 2025 |
| Anytime Care Solutions Limited | Health & social care | 2017 |
| AO Auto Car Sale Ltd | Wholesale & retail | 2025 |
| Aovihair Limited | Other services | 2025 |
| Ap&C Limited | Health & social care | 2015 |
| Apex Amari Consultancy Ltd | Administrative & support | 2022 |
| APEX4 Limited | Hospitality | 2026 |
| APF Group Limited | Construction | 2021 |
| Apfl Services Limited | Hospitality | 2020 |
| Apip Limited | Real estate | 2021 |
| APJ Financial Services Limited | Professional & scientific | 2012 |
| Apollo Architecture Ltd | Professional & scientific | 2020 |
| Apollo FP Limited | Construction | 2024 |
| Apollo Kitchens Ltd | Wholesale & retail | 2013 |
| Apostle Shoes Limited | Wholesale & retail | 2018 |
| Appans Cash & Carry Ltd | Wholesale & retail | 2023 |
| Applyarc Ltd | Information & communication | 2025 |
| Approved Electrical Installations Ltd | Other services | 2017 |
| April Steggles Consultancy Ltd | Professional & scientific | 2025 |
| Aprt Service Limited | Wholesale & retail | 2017 |
| Aqua Cleanse Essex Ltd | Administrative & support | 2026 |
| Aqua Resonance Wellness Ltd | Health & social care | 2026 |
| Aqua Tech Pressure Washing Ltd | Administrative & support | 2026 |
| Aqua Zone Swim School Ltd | Arts & recreation | 2025 |
| Aquablue Pools Limited | Administrative & support | 2004 |
| AR Photomaking Ltd | Professional & scientific | 2025 |
| Aras a Properties Limited | Real estate | 2026 |
| Arberia Construct Limited | Construction | 2020 |
| ARC Broadcasting Limited | Arts & recreation | 2019 |
| ARC Medical Design Limited | Manufacturing | 2008 |
| Arcaniia Labs Ltd | Information & communication | 2026 |
| Archangel Michael Holding Limited | Financial services | 2021 |
| Archelon Investigations Limited | Administrative & support | 2018 |
| Archers Law (Chelmsford) Ltd | Administrative & support | 2008 |
| Architectural Projects (Land & Securities) Limited | Real estate | 1971 |
| Arcpro Consultancy Ltd | Public administration | 2021 |
| Ardleigh Langham Limited | Financial services | 2015 |
| Ardleigh PUB Company Ltd | Hospitality | 2019 |
| Area F1 (Kings Hill) Management Company Limited | Households | 2015 |
| ARG Group Essex Limited | Construction | 2025 |
| Argyle Accounting Ltd | Professional & scientific | 2018 |
| ARI B Limited | Professional & scientific | 2015 |
| ARK Tech Services Ltd | Information & communication | 2015 |
| ARM Commercial Limited | Real estate | 2015 |
| Armin Holdings Limited | Financial services | 2024 |
| Armin Properties Limited | Real estate | 2024 |
| Armson Property Ltd | Real estate | 2019 |
| ARO Express Ltd | Transport & logistics | 2025 |
| Aroma House Takeaway Limited | Hospitality | 2019 |
| Art DE VIE SOS Ltd | Wholesale & retail | 2022 |
| Artec Fabrications Limited | Wholesale & retail | 1985 |
| Arterial House Limited | Administrative & support | 2026 |
| Arthouse Retreat Studio Ltd | Education | 2023 |
| Arthur KCM Ltd | Construction | 2023 |
| Arthurich Healthcare Services Ltd | Health & social care | 2023 |
| Artisan Cellars Limited | Construction | 2021 |
| Artisan People Beauty Ltd | Administrative & support | 2011 |
| Artistic Signs Limited | Administrative & support | 2003 |
| Arvelle Developments Limited | Construction | 2017 |
| Arya's Inclusive Care Limited | Health & social care | 2020 |
| Asgoodasitgets Limited | Administrative & support | 1998 |
| Ash-Lee Entertainment Ltd | Arts & recreation | 2021 |
| Ashingdon Gardens (Block B) Management Company Limited | Households | 1991 |
| Ashingdon Gardens (Block H) Management Company Limited | Households | 1992 |
| Ashingdon Gardens (Block N) Management Company Limited | Households | 1993 |
| Ashington Valeting Ltd | Other services | 2012 |
| Ashley Burley Ltd | Professional & scientific | 2023 |
| Ashora Ltd | Wholesale & retail | 2025 |
| Ashrie Property Ltd | Real estate | 2019 |
| Ashton Wallace Limited | Professional & scientific | 2024 |
| Asia Palace Rental Limited | Transport & logistics | 2019 |
| Asmr Traders Limited | Wholesale & retail | 2026 |
| Aspire Care London Ltd | Health & social care | 2018 |
| Aspire Strength & Conditioning Limited | Arts & recreation | 2024 |
| Associated Diamond Drilling Limited | Administrative & support | 2013 |
| Assured Care and Pharmaceuticals Limited | Health & social care | 2023 |
| Astral Apartments Limited | Households | 2010 |
| Astéri Aesthetics Limited | Other services | 2022 |
| Aswara Construction Ltd | Construction | 2019 |
| AT Aroga Ltd | Other services | 2014 |
| AT Seven Bar Ltd | Hospitality | 2026 |
| Atharveer Ltd | Wholesale & retail | 2025 |
| Athena Land & Property Limited | Real estate | 2015 |
| Athuj Ltd | Real estate | 2024 |
| Atkins Estates Ltd | Real estate | 2019 |
| Atkinson Aero Services Ltd | Manufacturing | 2025 |
| Atlantas Metalwork Installations Ltd | Construction | 2014 |
| Atlantic Scents Ltd. | Wholesale & retail | 2012 |