| ACS Construction Midlands Limited | Construction | 2007 |
| ACS Ecommerce Ltd | Wholesale & retail | 2024 |
| ACS ED Shelf 11 Limited | Extraterritorial | 2017 |
| ACS ED Shelf 5 Limited | Extraterritorial | 2020 |
| ACS ED Shelf 7 Limited | Extraterritorial | 2020 |
| ACS ED Shelf 8 Limited | Extraterritorial | 2017 |
| ACS Global College Ltd | Education | 2024 |
| ACS Global Consultants Limited | Education | 2024 |
| ACS Technologies Ltd | Information & communication | 2011 |
| ACT Care Service Ltd | Health & social care | 2023 |
| ACT Furniture Manufacturers Limited | Financial services | 1977 |
| ACT Holdings Limited | Financial services | 2023 |
| ACT on Care Ltd | Public administration | 2018 |
| ACT on Dyslexia Ltd | Other services | 2015 |
| ACT Transact Ltd | Financial services | 2025 |
| Act-Training Ltd | Education | 2024 |
| Actant Consortium Ltd | Professional & scientific | 2025 |
| Actavo (P.D.C.) Limited | Construction | 1998 |
| Actavo (UK) Limited | Manufacturing | 2000 |
| Actavo Building Solutions (UK) Limited | Construction | 2009 |
| Actavo Events (UK) Limited | Administrative & support | 2010 |
| Actavo Holdings (UK) Limited | Administrative & support | 2008 |
| Actemium UK Limited | Construction | 1900 |
| Actimise Limited | Real estate | 2025 |
| Acting to Revive Care Limited | Health & social care | 2025 |
| Action Driveways Ltd | Construction | 2024 |
| Action International Ministries (UK) | Health & social care | 1996 |
| Action LGV PCV Training Limited | Education | 2013 |
| Action Self Drive Limited | Administrative & support | 2006 |
| Action Starter Limited | Information & communication | 2012 |
| Action Transport Group Ltd | Transport & logistics | 2024 |
| Action Yemen Limited | Extraterritorial | 2023 |
| Actionben Entertainment Ltd | Administrative & support | 2025 |
| Actitrans UK Ltd | Administrative & support | 2026 |
| Activat Ltd | Professional & scientific | 2026 |
| Activate BDM Limited | Professional & scientific | 2018 |
| Activate Care Ltd | Health & social care | 2024 |
| Activate Power Service Ltd | Construction | 2021 |
| Activating Creative Talent C.I.C. | Education | 2012 |
| Activator Nutrition Limited | Manufacturing | 2025 |
| Active Advance Training Academy Ltd | Education | 2023 |
| Active Aero Drone Services Ltd | Professional & scientific | 2025 |
| Active Alarms Ltd | Administrative & support | 2012 |
| Active Bham CIC | Education | 2023 |
| Active Building Control Service Ltd | Professional & scientific | 2025 |
| Active Carbon Filters Ltd | Manufacturing | 2023 |
| Active Clinics Ltd | Other services | 2018 |
| Active Contractors & Plant Hire Limited | Construction | 2017 |
| Active Contruction Ltd | Construction | 2024 |
| Active Courses Ltd | Arts & recreation | 2017 |
| Active Extreme Ltd | Arts & recreation | 2019 |
| Active Grocery Limited | Wholesale & retail | 2025 |
| Active Group International Ltd | Wholesale & retail | 2016 |
| Active Heat Midlands Ltd | Energy | 2023 |
| Active Humanity Ltd | Other services | 2025 |
| Active in Arts Wellbeing CIC | Arts & recreation | 2025 |
| Active Listening for Wellbeing CIC | Administrative & support | 2014 |
| Active Management Solutions (2) Limited | Transport & logistics | 2012 |
| Active Management Solutions (3) Limited | Transport & logistics | 2013 |
| Active Management Solutions (4) Limited | Transport & logistics | 2013 |
| Active Management Solutions (5) Limited | Transport & logistics | 2015 |
| Active Management Solutions (7) Limited | Transport & logistics | 2016 |
| Active Management Solutions Ltd | Transport & logistics | 2011 |
| Active Market Ltd | Wholesale & retail | 2025 |
| Active Matter Ltd | Information & communication | 2017 |
| Active Nutrition Ltd | Health & social care | 2024 |
| Active Nutrition Online Ltd | Wholesale & retail | 2025 |
| Active Professional Healthcare Ltd | Health & social care | 2016 |
| Active Property Agents Ltd | Real estate | 2006 |
| Active Recovery&Courier Service Ltd | Transport & logistics | 2026 |
| Active Sport Group Ltd | Education | 2026 |
| Active Super Stars Ltd | Education | 2017 |
| Active Taxis Limited | Transport & logistics | 2016 |
| Active UK Properties Ltd | Real estate | 2020 |
| Active UP C.I.C. | Education | 2026 |
| Active Vehicle Care Ltd | Wholesale & retail | 2026 |
| Active Wellbeing Works Limited | Hospitality | 2020 |
| Activebase Art Limited | Wholesale & retail | 2017 |
| Actively Engaged Consultancy Ltd | Professional & scientific | 2019 |
| Activepine Limited | Construction | 1986 |
| Activeu Limited | Health & social care | 2020 |
| Actiview Optics Ltd | Health & social care | 2018 |
| Activitee Group Ltd | Financial services | 2025 |
| Activity Supplies Limited | Administrative & support | 2024 |
| Activo Care Limited | Health & social care | 2018 |
| Activo Real Estate Limited | Real estate | 2020 |
| Activo Services Ltd | Households | 2022 |
| Actl Holdings Limited | Professional & scientific | 2022 |
| Actoriax Discovery Ltd | Information & communication | 2026 |
| Acts 1724 Limited | Professional & scientific | 2018 |
| Acts and Entertainment Limited | Arts & recreation | 2008 |
| Acts Traders Ltd | Professional & scientific | 2018 |
| Actual Care Services Ltd | Health & social care | 2017 |
| Actual Homes Ltd | Real estate | 2025 |
| Actualized ME Ltd. | Public administration | 2021 |
| Actuary Insure Limited | Construction | 2014 |
| Actuate Services (GB) Ltd | Wholesale & retail | 2012 |
| Acuherbs Limited | Health & social care | 1999 |
| Acuity Finance Ltd | Professional & scientific | 2025 |
| Acumapro Limited | Professional & scientific | 2018 |