| Action Duchenne Limited | Health & social care | 2003 |
| Action for M.E. | Health & social care | 1994 |
| Action Force Pest Prevention Limited | Administrative & support | 2025 |
| Action Greater Bedminster Community Interest Company | Health & social care | 2025 |
| Action Hero | Arts & recreation | 2018 |
| Action Packed Adventures LLP | | 2025 |
| Action PAS Limited | Administrative & support | 2018 |
| Action Potential Group Ltd | Professional & scientific | 2016 |
| Action With Communities in Rural England | Other services | 1997 |
| ACTIV8 Information Security Limited | Information & communication | 2010 |
| ACTIV8 Property Management Ltd | Real estate | 2020 |
| Activate Utilities Ltd | Construction | 2017 |
| Activation Digital Ltd | Professional & scientific | 2010 |
| Active 8 Health & Fitness Limited | Health & social care | 2002 |
| Active AC Limited | Information & communication | 2018 |
| Active Analysis Limited | Administrative & support | 2016 |
| Active Case Managers Limited | Administrative & support | 1999 |
| Active CSD Ltd | Professional & scientific | 2024 |
| Active Design Solutions Limited | Manufacturing | 2012 |
| Active Employment Limited | Administrative & support | 1999 |
| Active Energy Advisers NW Ltd | Other services | 2022 |
| Active Financial Advice Ltd | Financial services | 2012 |
| Active Force Recruitment Ltd | Transport & logistics | 2009 |
| Active Giggles Bristol Limited | Arts & recreation | 2019 |
| Active Giggles Franchising Limited | Arts & recreation | 2019 |
| Active Group Media Limited | Administrative & support | 2025 |
| Active Legacy Ltd | Construction | 2022 |
| Active Medical Services Ltd | Health & social care | 2024 |
| Active Property Management Ltd | Real estate | 2025 |
| Active Travels Montenegro Ltd | Administrative & support | 2013 |
| Activebeing Limited | Other services | 2021 |
| Activity First CIC | Education | 2024 |
| Activus Limited | Professional & scientific | 1992 |
| Acton AID C.I.C. | Hospitality | 2018 |
| Acton Auto Maintenance Ltd | Wholesale & retail | 2021 |
| Acton Homes Limited | Construction | 2001 |
| Actuated Limited | Manufacturing | 2008 |
| Actuation LAB Ltd | Professional & scientific | 2018 |
| Actuatus Systems Ltd | Extraterritorial | 2023 |
| ACU Group Limited | Manufacturing | 2018 |
| Acumen and Acuity Ltd | Professional & scientific | 2015 |
| Acumet Limited | Information & communication | 2024 |
| Acute Design Windows Doors & General Builders Ltd | Construction | 2022 |
| Acute Scaffold Design Ltd | Professional & scientific | 2024 |
| ACV Electrical Ltd | Construction | 2022 |
| AD Art Design Limited | Manufacturing | 1991 |
| AD Ascent Developments Ltd | Construction | 2026 |
| AD Astra Aviation Limited | Professional & scientific | 2025 |
| AD Bookkeeping Services Limited | Professional & scientific | 2013 |
| AD Consultancy Group (Essex) Ltd | Professional & scientific | 2019 |
| AD Consultancy Group Ltd | Professional & scientific | 2019 |
| AD Consultancy Group SW Limited | Professional & scientific | 2019 |
| AD Housekeeping Ltd | Administrative & support | 2024 |
| AD LIB Holdings Limited | Administrative & support | 2004 |
| AD Nights Ltd | Real estate | 2025 |
| AD Piccadilly Ltd | Hospitality | 2022 |
| AD Premium Cars Ltd | Wholesale & retail | 2025 |
| AD Slade Enterprises Limited | Other services | 2020 |
| AD Trading Limited | Transport & logistics | 2025 |
| ADA Lena Heating Ltd | Construction | 2020 |
| Adam & Rebecca Ltd | Administrative & support | 2024 |
| Adam 20 Limited | Wholesale & retail | 2024 |
| Adam Bahadur Limited | Health & social care | 2018 |
| Adam Church Limited | Real estate | 2009 |
| Adam Finn Consultancy Limited | Professional & scientific | 2023 |
| Adam Harris ARB Limited | Professional & scientific | 2024 |
| Adam Hawkins Transport Limited | Transport & logistics | 2023 |
| Adam House (UK) Limited | Professional & scientific | 2007 |
| Adam House Property Operations Ltd | Real estate | 2025 |
| Adam M Cummings Ltd | Wholesale & retail | 2023 |
| Adam Schapiro & Co Limited | Construction | 2022 |
| Adam U.K Ltd | Wholesale & retail | 2025 |
| Adam Vincent Hair Ltd | Other services | 2019 |
| Adam's Autos Bristol Ltd | Wholesale & retail | 2024 |
| Adamant (Clevedon) Limited | Real estate | 2017 |
| Adamant (Shepton) Limited | Real estate | 2016 |
| Adamant (Triangle) Limited | Real estate | 2018 |
| Adamant (Wickwar) Limited | Real estate | 2019 |
| Adamant Building Services Ltd | Administrative & support | 2022 |
| Adamant Developments Ltd | Construction | 2007 |
| Adamant Visuals Limited | Information & communication | 2024 |
| Adamek Property Ltd | Real estate | 2017 |
| Adamfort Ltd | Real estate | 2024 |
| Adami Holdings Ltd | Financial services | 2026 |
| Adamjbarber Ltd | Information & communication | 2019 |
| Adams Digital Network Ltd | Information & communication | 2021 |
| Adams Export Limited | Administrative & support | 2025 |
| Adams Funeral Directors Ltd | Other services | 2018 |
| Adams Heritage Estates Ltd | Real estate | 2025 |
| Adams Mini Market Limited | Wholesale & retail | 2025 |
| Adams Motors & Repair Limited | Wholesale & retail | 2025 |
| Adams Root & Associates Limited | Real estate | 2003 |
| Adams Root Limited | Professional & scientific | 2023 |
| Adams Taxi Hire Limited | Administrative & support | 2023 |
| Adamscom Limited | Professional & scientific | 2026 |
| Adam’S Recovery and Storage Ltd | Wholesale & retail | 2025 |
| Adam’S Twelve Ltd | Hospitality | 2024 |
| Adapt Inc. Limited | Information & communication | 2021 |
| Adapt Planning Ltd | Professional & scientific | 2023 |
| Adapt Programme Services Ltd | Information & communication | 2024 |