| Arivian Property Group Ltd | Real estate | 2026 |
| Armanacasa Ltd | Real estate | 2025 |
| Armour Transport Limited | Transport & logistics | 2018 |
| Arnhem Architectural Services Limited | Construction | 2008 |
| Arno Business Communications Limited | Professional & scientific | 2003 |
| Arose Finance Limited | Financial services | 2021 |
| Arpanet Limited | Manufacturing | 1991 |
| Arresting Enterprises Limited | Hospitality | 2015 |
| Arrigonfrutta Limited | Real estate | 1973 |
| Arrowsgate Ltd | Administrative & support | 2022 |
| ARS Letting Agents Limited | Households | 2024 |
| Artisan Candles Ltd | Manufacturing | 2008 |
| Arvo Electrical Limited | Construction | 2023 |
| Asante and Canadas Ltd | Real estate | 2026 |
| Asbestos Management Limited | Professional & scientific | 2005 |
| Asbestos Management Services Group Ltd | Other services | 2022 |
| Ascott ETC Ltd | Professional & scientific | 2015 |
| Ashmart Ltd | Administrative & support | 2009 |
| Ashridge Grange Limited | Construction | 2021 |
| Ashwells Reclaimed Timber Ltd | Water & waste | 2018 |
| ASK Learn & Develop Limited | Education | 2006 |
| ASL Vets Limited | Professional & scientific | 2015 |
| ASM Housing Ltd | Real estate | 2024 |
| Asmatt Limited | Construction | 2004 |
| Aspen Joinery & Design Ltd | Manufacturing | 2021 |
| Aspley Law Limited | Professional & scientific | 2009 |
| Asserve Limited | Administrative & support | 2015 |
| Assetpro Management Group Ltd | Real estate | 2024 |
| Assured GAS UK Ltd | Construction | 2018 |
| Assured Properties and Investments Limited | Construction | 1992 |
| Astar Space Ltd | Arts & recreation | 2026 |
| Astraa Ltd | Construction | 2015 |
| Astral Lodge Limited | Health & social care | 2016 |
| Astro Connections Limited | Information & communication | 2025 |
| Atan RAD Limited | Health & social care | 2021 |
| Atcost Ltd | Construction | 2020 |
| Atelier M3 Ltd | Professional & scientific | 2020 |
| Athp Solutions Ltd | Construction | 2024 |
| ATL Prop Ltd | Construction | 2022 |
| Atlantis Quality Homes Ltd | Construction | 2014 |
| Atlantis Quality Housing Ltd | Real estate | 2019 |
| Atlantisrealm Limited | Other services | 2012 |
| Atlas Roofing Services Ltd | Construction | 2022 |
| ATS Global Logistics Limited | Transport & logistics | 2025 |
| Attawa Properties Ltd | Households | 2024 |
| ATW Plumbing and Heating Ltd | Construction | 2024 |
| Au-Hmh Limited | Health & social care | 2019 |
| Aurelia London Limited | Wholesale & retail | 2022 |
| Aurora 88 Limited | Professional & scientific | 2016 |
| Ausonia Nurseries Limited | Agriculture & fishing | 1998 |
| Austen Company Limited | Real estate | 2025 |
| Auto JET Limited | Administrative & support | 2009 |
| AV Skyline Limited | Construction | 2026 |
| Aventura Ebooks Limited | Information & communication | 2011 |
| Avenue Windows Ltd | Construction | 2020 |
| Avery Electrical Limited | Construction | 2007 |
| Avitar Services Limited | Mining & quarrying | 2001 |
| AVK Group Ltd | Financial services | 2021 |
| AWE Smithfield Ltd | Financial services | 2023 |
| AWJ Resourcing Limited | Administrative & support | 2008 |
| Axiom Management Team Limited | Information & communication | 2014 |
| Axometa Retail Trading Ltd | Wholesale & retail | 2026 |
| Axon Physio Limited | Health & social care | 2018 |
| Ayumi Ltd | Information & communication | 2019 |
| AZ Transport(Uk) Ltd | Transport & logistics | 2017 |
| AZZ Global Ltd | Transport & logistics | 2026 |
| B Construction Planning Limited | Administrative & support | 2012 |
| B Curtis & Partners LLP | | 2011 |
| B Kaylor Ltd | Education | 2011 |
| B M Vehicle Maintenance Limited | Wholesale & retail | 2008 |
| B Smash Ltd | Wholesale & retail | 2020 |
| B Walsh Solutions Limited | Construction | 2007 |
| B-Squared IT Consulting Ltd | Information & communication | 2025 |
| B-Tec Limited | Construction | 2009 |
| B.Per Consulting Ltd | Professional & scientific | 2015 |
| B3G (Build) Ltd | Construction | 2021 |
| B3G (Group) Ltd | Construction | 2020 |
| B3G (Mgmt) Ltd | Construction | 2021 |
| B3TA Living Ltd | Real estate | 2021 |
| Baba Lucia Limited | Other services | 2024 |
| Baker's Installations Limited | Construction | 2019 |
| Bakers Court (Ramsden Heath) Essex Limited | Administrative & support | 2009 |
| Balanced Personal Training Solutions Limited | Health & social care | 2014 |
| Bancroft Nominees Limited | Real estate | 2023 |
| Bandedge Limited | Construction | 1990 |
| Barleylands Glassworks Ltd. | Manufacturing | 1997 |
| Barnway Consultants Ltd | Professional & scientific | 2013 |
| Bartlett Financial Services Limited | Professional & scientific | 2010 |
| Basildon Business Leaders CIC | Other services | 2024 |
| Basildon Garden & Mower Centre Ltd | Other services | 2020 |
| Basildon United Football, Sports & Leisure Limited | Arts & recreation | 2025 |
| Basildon UTD Football Club Ltd | Arts & recreation | 2023 |
| Basse Solutions Ltd | Administrative & support | 2019 |
| Battersea Engineering Ltd | Construction | 2021 |
| BAW Property Limited | Real estate | 2018 |
| Bay Tree Garden Group Limited | Agriculture & fishing | 2020 |
| BBE MAC Solutions Limited | Information & communication | 2018 |
| BBM Capital Limited | Financial services | 2017 |
| BBM Homes Ltd | Real estate | 2025 |
| BBQ Butcher Limited | Wholesale & retail | 2024 |