| Access Design and Engineering Limited | Professional & scientific | 1988 |
| Access Homes LLP | | 2007 |
| Access Image Security Limited | Other services | 2018 |
| Access Knowledge Solutions Limited | Professional & scientific | 2016 |
| Accessible Hire and Refrigeration Limited | Administrative & support | 1993 |
| Accessories in Style Limited | Hospitality | 2019 |
| Acclaim Clinical Consulting Ltd | Professional & scientific | 2024 |
| Acclaim OT Limited | Health & social care | 2020 |
| Accountancywala Ltd | Professional & scientific | 2025 |
| Accounteam Ltd | Information & communication | 2022 |
| Accrington Plastics Ltd | Extraterritorial | 2010 |
| ACD Fletcher Holdings Ltd | Information & communication | 2025 |
| Ace of Cards Ltd | Wholesale & retail | 2021 |
| Ace of Spades Properties Limited | Real estate | 2021 |
| Ace Sports Camps Ltd | Health & social care | 2025 |
| Acedrives Tarmacadam Surfacing Contractors Limited | Wholesale & retail | 1977 |
| Acema Marketing Limited | Information & communication | 2021 |
| Acer Project Management Ltd | Extraterritorial | 2023 |
| ACF Car Finance Limited | Wholesale & retail | 2003 |
| Achiever Lims Ltd | Extraterritorial | 2025 |
| Achiever Medical Limited | Information & communication | 2007 |
| Achiever Software Limited | Professional & scientific | 2003 |
| Achill Spa Ltd | Other services | 2022 |
| Acknowledge Building Services Limited | Real estate | 2017 |
| Ackor Contracting Limited | Construction | 2023 |
| ACL Horizons Limited | Professional & scientific | 2025 |
| Acoma Property Ltd | Real estate | 2023 |
| Acorn Accounting & Bookkeeping Limited | Extraterritorial | 2018 |
| Acquiris Property Limited | Real estate | 2024 |
| Acquisitions & Alliances International Limited | Professional & scientific | 1996 |
| Acra Investment Holdings Limited | Financial services | 2025 |
| Acre Wood Housing Ltd | Health & social care | 2020 |
| Acrusis Limited | Other services | 2015 |
| Acta Solutions Ltd | Construction | 2020 |
| Actawin Ltd | Information & communication | 2017 |
| Actea Consultancy Ltd | Professional & scientific | 2026 |
| Action Dashboards Limited | Information & communication | 2023 |
| Action for Congo's Mothers and Children Ltd | Education | 2011 |
| Activ Sports Badminton Ltd | Education | 2024 |
| Activation Energy Limited | Professional & scientific | 2017 |
| Active Angels Limited | Administrative & support | 2008 |
| Active Horizons Ltd | Education | 2025 |
| Active Property Holdings Limited | Real estate | 2025 |
| Active Sports Trust Limited | Arts & recreation | 2011 |
| Activebiz Information Systems Limited | Information & communication | 2012 |
| Activities for Kidz Ltd | Wholesale & retail | 2020 |
| Acts Simply Functioning Limited | Hospitality | 2001 |
| Acumen Commercial Insights Ltd. | Professional & scientific | 2006 |
| Acurelax Centre Ltd | Other services | 2022 |
| Acute Medicine Training Ltd | Health & social care | 2024 |
| AD HOC Legal Ltd | Administrative & support | 2017 |
| AD Landscaping Ltd | Administrative & support | 2026 |
| AD LED Media Limited | Professional & scientific | 2019 |
| ADA Parmar Ltd | Wholesale & retail | 2024 |
| Adam Dyson Engineering Services Limited | Professional & scientific | 2013 |
| Adam Executive Cars Limited | Administrative & support | 2018 |
| Adam's Tree Surgery Ltd | Agriculture & fishing | 2013 |
| Adams Prescribing Ltd | Health & social care | 2025 |
| Adan Properties Ltd | Real estate | 2024 |
| Adapta Solutions Limited | Information & communication | 2015 |
| Adaptive Life Sciences Limited | Hospitality | 2023 |
| Adderley Park Ltd | Financial services | 2025 |
| Addfrost Maintenance Services Limited | Energy | 1998 |
| Additions Design Studio Ltd | Construction | 2015 |
| Addl Property Developments Limited | Construction | 2022 |
| Addo Solutions Limited | Professional & scientific | 2025 |
| Addtek Estates Ltd | Real estate | 2026 |
| Addtek Limited | Information & communication | 2024 |
| Aden Maintenance Ltd | Manufacturing | 2024 |
| Adepan Estate Limited | Real estate | 2025 |
| Adepan IT Limited | Information & communication | 2024 |
| Adept Construction Ltd | Construction | 2025 |
| Adeptus Partners Ltd | Information & communication | 2024 |
| ADH Construction Ltd | Construction | 2018 |
| Adiri Tech Ltd | Professional & scientific | 2026 |
| Adjd Business Solutions Limited | Administrative & support | 2019 |
| Adjuto Limited | Information & communication | 2009 |
| Adkins Auto Ltd | Wholesale & retail | 2025 |
| Admantex Accountancy Limited | Information & communication | 2024 |
| Admin Alliance Limited | Wholesale & retail | 2005 |
| Adoption IS 4 U CIC | Other services | 2023 |
| Ados Sightcare Limited | Health & social care | 2003 |
| ADP & Co Ltd | Extraterritorial | 2012 |
| ADP UK Investments Limited | Real estate | 2026 |
| ADR Home Services Ltd | Construction | 2025 |
| ADR Plant Hire and Repair Limited | Administrative & support | 2026 |
| Adrian Connelly Wealth Management Limited | Financial services | 2013 |
| Adrian Kettle Limited | Professional & scientific | 2013 |
| Adrian Styles Holdings Limited | Financial services | 2021 |
| Adrm Holdings Limited | Professional & scientific | 2021 |
| Adroit Automotive Limited | Transport & logistics | 2025 |
| ADS Technologies Limited | Information & communication | 2016 |
| Adsa Medical Consulting Ltd | Health & social care | 2012 |
| Adsu Medical Limited | Health & social care | 2020 |
| Advance Contracting Limited | Construction | 2004 |
| Advance Physiotherapy Group Ltd | Health & social care | 2020 |
| Advanced Communication Systems Limited | Professional & scientific | 1990 |
| Advanced Construction Systems Limited | Wholesale & retail | 2006 |
| Advanced Digital Technology (U.K.) Limited | Professional & scientific | 1983 |
| Advanced Field Applications Ltd | Information & communication | 2006 |