| Accounting Services Taxa Ltd | Professional & scientific | 2016 |
| Accounts Payable News Ltd | Information & communication | 2008 |
| Acctax Solutions Limited | Professional & scientific | 2000 |
| Accura Consultancy Ltd | Information & communication | 2025 |
| Accurate Finance Limited | Administrative & support | 2024 |
| Accurate Instruments Ltd | Wholesale & retail | 2020 |
| Accurate Inventories Limited | Other services | 2013 |
| Accuscript Consultancy Limited | Information & communication | 2015 |
| Ace Care Services Limited | Health & social care | 2021 |
| Ace Cars Reading Ltd | Transport & logistics | 2022 |
| Ace Clvrk Entertainment Ltd | Arts & recreation | 2025 |
| Ace Conctracts Ltd | Construction | 2025 |
| Ace Disc Golf Ltd | Wholesale & retail | 2019 |
| Ace Global Management Services Ltd | Construction | 2013 |
| Ace in the Hole Ltd | Wholesale & retail | 2021 |
| Ace Investment Consulting Ltd | Administrative & support | 2016 |
| Ace Investments (London) Ltd | Construction | 2016 |
| Ace Management Consultancy Limited | Professional & scientific | 2020 |
| Ace Realty Management Limited | Real estate | 2021 |
| Ace Trade Limited | Information & communication | 2008 |
| Ace UK Engineering Consultants Ltd | Professional & scientific | 2020 |
| Ace Veterinary Supplies Ltd | Wholesale & retail | 2012 |
| Ace Wheelchair Travel Limited | Transport & logistics | 2020 |
| Acemoglu UK Ltd | Hospitality | 2015 |
| Acenseo Limited | Information & communication | 2004 |
| Acersteel Ltd | Manufacturing | 2018 |
| Aces Organisation Ltd | Administrative & support | 2019 |
| Acetech Enterprises Limited | Professional & scientific | 2001 |
| Achieve Connect | Education | 1995 |
| Achieve CTC Ltd | Professional & scientific | 2025 |
| Achieve Projects Limited | Professional & scientific | 2013 |
| Achieve Therapy Ltd | Other services | 2015 |
| Achilleos Consulting Ltd | Information & communication | 2025 |
| Achilleus DE Cruz Limited | Wholesale & retail | 1978 |
| ACI Occupational Health Limited | Health & social care | 2012 |
| Acia Aero Capital (UK) Limited | Financial services | 2017 |
| Acia Aero Leasing (UK) Limited | Financial services | 2017 |
| Acia Aero Leasing North Sea Limited | Administrative & support | 2022 |
| Acid Digital Ltd | Professional & scientific | 2024 |
| ACJ Trans Ltd | Transport & logistics | 2018 |
| Ackar Limited | Health & social care | 2026 |
| Ackender Hill (Alton) Management Company Limited | Households | 2019 |
| Acme Consulting Ltd | Information & communication | 2019 |
| Acme Packet UK Limited | Professional & scientific | 2004 |
| Acme Realty Limited | Real estate | 2024 |
| Acme Speedshop Ltd | Wholesale & retail | 2025 |
| Acoloca Limited | Manufacturing | 2004 |
| Acommerce Ltd | Wholesale & retail | 2022 |
| Aconex (UK) Limited | Information & communication | 2003 |
| Aconex Services Limited | Information & communication | 1995 |
| Acorn IT Systems Limited | Information & communication | 2010 |
| Acorn Partnership Limited | Information & communication | 2004 |
| Acorn Realty Ltd | Real estate | 2024 |
| Acorn to Oak Environmental Ltd | Administrative & support | 2022 |
| Acorn Tutors Limited | Education | 2014 |
| Acornceramics. Ltd | Manufacturing | 2017 |
| Acosy Bumpers Ltd | Wholesale & retail | 2012 |
| Acquestra (Pangbourne) Limited | Real estate | 2023 |
| Acquestra (Pell Street) Limited | Real estate | 2025 |
| Acquisition U.K. Limited | Professional & scientific | 2002 |
| Acre Housing | Hospitality | 1992 |
| Acrobyte Ltd | Information & communication | 2016 |
| Acronym Edit and Production Limited | Information & communication | 2010 |
| Across Cultures Ltd | Education | 2012 |
| ACS Hydrocarbons Limited | Mining & quarrying | 2014 |
| Acsc Transport Ltd | Transport & logistics | 2024 |
| ACT Sustainability Ltd | Professional & scientific | 2018 |
| Actibux Ltd | Information & communication | 2026 |
| Actinium CS Limited | Professional & scientific | 2005 |
| Actinium Holdings Ltd | Financial services | 2025 |
| Action B Ltd | Information & communication | 2019 |
| Action Boats Ltd | Information & communication | 2026 |
| Action Marketing Works Limited | Professional & scientific | 2024 |
| Action Stations Marketing Limited | Professional & scientific | 2000 |
| ACTION4 Limited | Other services | 1997 |
| ACTIV8 Rehab Limited | Health & social care | 2004 |
| Activate Learning Education Trust | Education | 2013 |
| Activate NOW Training Services Ltd | Education | 2024 |
| Active Business Training Limited | Information & communication | 1999 |
| Active Core Group Limited | Arts & recreation | 2026 |
| Active Defence Limited | Professional & scientific | 2018 |
| Active Domestic Appliances Ltd | Other services | 2012 |
| Active Facilities Management Ltd. | Administrative & support | 1999 |
| Active House Solutions Limited | Construction | 2020 |
| Active Investments (Reading) Limited | Financial services | 1995 |
| Active Leader Operations Limited | Arts & recreation | 2018 |
| Active Leaders Limited | Education | 2017 |
| Active Life Mobility Ltd | Wholesale & retail | 2025 |
| Active Load International Limited | Manufacturing | 2018 |
| Active Property Invest Ltd | Real estate | 2025 |
| Active Tools Limited | Manufacturing | 2003 |
| Active Value Investments Ltd | Professional & scientific | 2025 |
| Active-Pcb Solutions Limited | Manufacturing | 1997 |
| Activeops Overseas Limited | Information & communication | 2010 |
| Activeops PLC | Information & communication | 1995 |
| Actonomous Ltd | Information & communication | 2026 |
| Actsight Limited | Information & communication | 2025 |
| Acttrident Ltd. | Information & communication | 2026 |
| Actualise Law Ltd | Professional & scientific | 2020 |
| Actualizing Ltd | Health & social care | 2022 |