| Access in Dudley | Health & social care | 2007 |
| Access Made Simple Limited | Construction | 2005 |
| Accessafe UK Ltd | Manufacturing | 2022 |
| Accessible Payment Solutions Ltd | Financial services | 2020 |
| Accomplish Acquico Ltd | Financial services | 2022 |
| Accomplish Group (Eilat) Limited | Health & social care | 2016 |
| Accomplish Group Bidco Limited | Financial services | 2014 |
| Accomplish Group Care Limited | Health & social care | 2006 |
| Accomplish Group Contract Management Limited | Health & social care | 2003 |
| Accomplish Group Cymru Lifestyles South Limited | Health & social care | 2007 |
| Accomplish Group Employee Limited | Health & social care | 2015 |
| Accomplish Group Holdco Limited | Financial services | 2014 |
| Accomplish Group Interco Limited | Financial services | 2014 |
| Accomplish Group Lifestyles (South West) Limited | Health & social care | 2006 |
| Accomplish Group Lifestyles Limited | Health & social care | 2003 |
| Accomplish Group Limited | Health & social care | 1987 |
| Accomplish Group Midco Limited | Financial services | 2014 |
| Accomplish Group Property Limited | Health & social care | 2003 |
| Accomplish Group Residential Care Limited | Health & social care | 2007 |
| Accomplish Group Specialist Care Limited | Health & social care | 2011 |
| Accomplish Group Support Limited | Health & social care | 1987 |
| Accomplish Mipco Limited | Financial services | 2022 |
| Accounts & Tax Simplified Ltd | Professional & scientific | 2025 |
| Accralite Limited | Extraterritorial | 2003 |
| Accredited AV Limited | Information & communication | 2010 |
| Ace Networks Solutions Ltd | Construction | 2022 |
| Ace of Bladez Ltd | Other services | 2021 |
| Ace Paving and Patios Ltd | Construction | 2022 |
| Ace Paving Ltd | Construction | 2018 |
| Ace Projects Ltd | Construction | 2023 |
| Ace Wealth & Developments Ltd | Professional & scientific | 2022 |
| Acgfreight Ltd | Transport & logistics | 2021 |
| Acme Professionals Limited | Professional & scientific | 2017 |
| Acorn Blackcountry Developments Limited | Construction | 1999 |
| Acorn Joinery Services Limited | Construction | 2004 |
| Acorn Maintenance Systems Limited | Wholesale & retail | 2002 |
| Acren Catering Services Limited | Hospitality | 2022 |
| Acren Services Limited | Real estate | 2018 |
| Acsys Lasertechnik UK Limited | Manufacturing | 2012 |
| Action Sports Events Ltd | Professional & scientific | 2016 |
| Action Sports Timing Ltd | Professional & scientific | 2016 |
| Active Black Country Limited | Other services | 2022 |
| Acuity HR Limited | Administrative & support | 2023 |
| AD 2000 Computing Limited | Administrative & support | 1997 |
| AD Financial Services Limited | Financial services | 2021 |
| AD Squared Leisure Ltd | Hospitality | 2026 |
| Adam Jones Investments Limited | Professional & scientific | 2005 |
| Adam Jones Properties Limited | Real estate | 2004 |
| Adam Nash Limited | Real estate | 2019 |
| Adam Philipson Limited | Professional & scientific | 2018 |
| Adams Assessors Limited | Professional & scientific | 2008 |
| Adaptable Finance Limited | Professional & scientific | 2018 |
| ADHD360 Limited | Information & communication | 2018 |
| ADP Carpet Distribution Limited | Financial services | 2020 |
| ADP Distribution Limited | Transport & logistics | 2005 |
| ADP Fulfilment Limited | Hospitality | 2018 |
| Adroit Commercial Limited | Extraterritorial | 2024 |
| Adroit Group Limited | Real estate | 1953 |
| ADS Ortho Limited | Health & social care | 2023 |
| ADS Properties Limited | Construction | 2012 |
| Adsash Health Care Ltd | Health & social care | 2026 |
| ADT Partners Limited | Financial services | 2021 |
| Advance Beyond Community Interest Company | Education | 2023 |
| Advanced Maintenance Supplies Limited | Wholesale & retail | 1998 |
| Advanced Verification Monitoring Limited | Real estate | 2003 |
| Advent IM Limited | Information & communication | 2002 |
| Adventureready Ltd | Information & communication | 2025 |
| Advocult Motorsport Limited | Wholesale & retail | 2019 |
| Aega Plus Ltd | Construction | 2024 |
| Aerohire Flight Training Limited | Education | 2025 |
| Aerohire Limited | Administrative & support | 1991 |
| Aesthetically YOU by Hayley Ltd | Other services | 2025 |
| Aesthetics by Beauty Essentials Ltd | Other services | 2022 |
| Affordable Essential Ltd | Wholesale & retail | 2025 |
| Afonso Films Ltd | Information & communication | 2026 |
| Afreco Tours Ltd | Administrative & support | 2006 |
| AG First Contractors Ltd | Other services | 2018 |
| AGA Management Ltd | Real estate | 2006 |
| AGE Care Technologies Limited | Information & communication | 2018 |
| Agency Disrupt Ltd | Professional & scientific | 2024 |
| Agentertainers Limited | Arts & recreation | 2024 |
| Agility Health Limited | Wholesale & retail | 2024 |
| Agricova Limited | Wholesale & retail | 2018 |
| Agrivalve Ltd | Wholesale & retail | 2024 |
| AGS and Daughters Limited | Wholesale & retail | 2022 |
| AGW Electrical (Services) Limited | Construction | 2006 |
| AH Plant LLP | | 2010 |
| Ahhfox Limited | Health & social care | 2018 |
| AHZ Holding Limited | Financial services | 2025 |
| Ai&Mu Limited | Wholesale & retail | 2025 |
| AIC Properties Limited | Real estate | 2017 |
| Aiden Zagros Ltd | Other services | 2026 |
| AIJ Land Limited | Real estate | 2017 |
| Air Brake Direct Ltd | Administrative & support | 2010 |
| Air Force Pro Ltd | Wholesale & retail | 2024 |
| Aireasetravel Limited | Administrative & support | 2026 |
| Airtool Sales and Services Limited | Manufacturing | 2008 |
| Aisi Integrations Ltd | Administrative & support | 2024 |
| AJ Automotive Ltd | Wholesale & retail | 2020 |
| AJ Lacey Project Management Ltd | Construction | 2025 |