| Astisor Limited | Real estate | 2017 |
| Astk Ltd | Wholesale & retail | 2017 |
| Astolfi UK Ltd | Construction | 2017 |
| Aston Stacey Consulting Limited | Administrative & support | 2020 |
| Astor (Bristol) Limited | Wholesale & retail | 2001 |
| Astra Biotech Ltd | Administrative & support | 2016 |
| Astra Design and Build Ltd | Construction | 2011 |
| Astra Developments (Bristol) Ltd | Construction | 2025 |
| Astra Electrical Contractors Limited | Construction | 1986 |
| Astra Software Development Limited | Information & communication | 2025 |
| Astral Consulting Services Limited | Professional & scientific | 2015 |
| Astral Neutronics Ltd | Manufacturing | 2021 |
| Astral Radio Ltd | Information & communication | 2025 |
| Astreahill Derivatives Ltd | Administrative & support | 2011 |
| Astro Enterprises Ltd | Wholesale & retail | 2023 |
| Astro Salus Education Limited | Administrative & support | 2013 |
| Astro Surveys Ltd | Professional & scientific | 2016 |
| Astron Fire and Security Limited | Wholesale & retail | 2010 |
| Astropulvis Limited | Financial services | 2021 |
| Astroserendipity Ltd | Extraterritorial | 2023 |
| Astrotrac Limited | Manufacturing | 2006 |
| Astroz Limited | Wholesale & retail | 2023 |
| Astrum Consulting Limited | Information & communication | 2013 |
| Asts Bristol Limited | Hospitality | 2020 |
| Astute Management Solutions Ltd | Construction | 2009 |
| Astute Technologies Ltd | Information & communication | 2007 |
| Asurus Limited | Professional & scientific | 2025 |
| ASV Emerson Bristol Limited | Wholesale & retail | 2022 |
| ASV Gloucester Limited | Wholesale & retail | 2022 |
| ASZ Architetti LLP | | 2014 |
| AT Design UK Limited | Information & communication | 2026 |
| AT Events Limited | Administrative & support | 2016 |
| AT Home With Hemmings Limited | Real estate | 2023 |
| AT Land Projects Ltd | Real estate | 2025 |
| AT Marketing Y.K Limited | Wholesale & retail | 2023 |
| AT Ortho Limited | Professional & scientific | 2014 |
| AT South West Ltd | Construction | 2025 |
| AT the Heart of Health Ltd | Extraterritorial | 2015 |
| AT Your Cost Limited | Hospitality | 2019 |
| At&T Istel Pension Trustee Limited | Other services | 1989 |
| Atalakit Ltd | Information & communication | 2019 |
| Atalara Ltd | Real estate | 2022 |
| Atalaygoctattoo Limited | Arts & recreation | 2025 |
| Atamis Ltd | Information & communication | 2009 |
| Ataye Systems Ltd | Professional & scientific | 2016 |
| ATB - Folio Print & Packaging Solutions Limited | Manufacturing | 2020 |
| ATB Contracting Limited | Construction | 2021 |
| ATB Industrial Ltd | Professional & scientific | 2011 |
| ATC Systems (International) Limited Partnership | | 2009 |
| ATD Designs Ltd | Professional & scientific | 2010 |
| ATD Geoscience Ltd | Mining & quarrying | 2020 |
| ATD Training Ltd | Education | 2025 |
| Atech Industries Bristol Limited | Professional & scientific | 2024 |
| Atelier Ellis Ltd | Manufacturing | 2021 |
| Atelier Form Ltd | Professional & scientific | 2021 |
| ATELIER29 Ltd | Information & communication | 2024 |
| Atex Media Limited | Information & communication | 1980 |
| Atfi Consulting Ltd | Professional & scientific | 2026 |
| ATG Haus Ltd | Wholesale & retail | 2019 |
| Atgl International Limited | Wholesale & retail | 2023 |
| Atgp (Bristol) Ltd | Wholesale & retail | 2024 |
| Athelai Edge (Down Hatherley) Management Company Limited | Households | 2023 |
| Athena Cards Ltd | Wholesale & retail | 2025 |
| Athena Neurology Limited | Health & social care | 2020 |
| Athena Projects Limited | Real estate | 2019 |
| Athena Suites Ltd | Hospitality | 2025 |
| Atherton Medical & Legal Ltd | Health & social care | 2019 |
| Atherton Rowe Ltd | Professional & scientific | 2012 |
| Athletes Journey Home UK Ltd | Health & social care | 2024 |
| Athraa Limited | Health & social care | 2011 |
| Athugala Ceylon Ltd | Hospitality | 2023 |
| Athusoft Ltd. | Information & communication | 2025 |
| ATK Gardens Limited | Extraterritorial | 2018 |
| ATK Homes Limited | Real estate | 2024 |
| ATK Removals Ltd | Transport & logistics | 2024 |
| Atkins Walters & Webster Limited | Professional & scientific | 1998 |
| Atkinson's Spa Limited | Other services | 2024 |
| Atlanta Designs Ltd | Manufacturing | 2023 |
| Atlantic Airlines Limited | Professional & scientific | 2008 |
| Atlantic Bridge Partners Limited | Professional & scientific | 2020 |
| Atlantic Consulting Group Ltd | Professional & scientific | 2026 |
| Atlantic Drylining & Painting Ltd | Construction | 2025 |
| Atlantic Forest Conservation CIC | Health & social care | 2025 |
| Atlantic Group International Limited | Transport & logistics | 2016 |
| Atlantic Linen Services Limited | Other services | 2004 |
| Atlantic Roller Consulting Ltd | Professional & scientific | 2018 |
| Atlanticpond Ltd | Wholesale & retail | 2020 |
| Atlantis Diffusion Ltd | Financial services | 2013 |
| Atlantis Voyage Ltd | Real estate | 2026 |
| Atlas & Chilli Ltd | Professional & scientific | 2025 |
| Atlas at Cars Ltd | Wholesale & retail | 2024 |
| Atlas Audio Ltd. | Extraterritorial | 2022 |
| Atlas Automation Controls Limited | Professional & scientific | 2025 |
| Atlas Court Estate Management Limited | Real estate | 2016 |
| Atlas Digital Media Ltd | Professional & scientific | 2025 |
| Atlas Global Software Limited | Administrative & support | 2015 |
| Atlas Heating (Bristol) Limited | Construction | 2013 |
| Atlas Industrial Removals Limited | Construction | 1988 |
| Atlas Investment Group Ltd | Construction | 2019 |
| Atlas Morse Limited | Administrative & support | 2019 |