| A Joy to Work With Ltd | Administrative & support | 2024 |
| A M Nettech Limited | Information & communication | 2024 |
| A Neill Consulting Limited | Professional & scientific | 2019 |
| A P Jones & Sons Ltd | Administrative & support | 2024 |
| A Pariente Consulting Limited | Professional & scientific | 2013 |
| A Pariente Property Management Limited | Real estate | 2017 |
| A R a Rodriguez Limited | Health & social care | 2023 |
| A S a P Publishing Limited | Information & communication | 2000 |
| A S People Solutions Limited | Professional & scientific | 2008 |
| A Stevens Plant Hire Ltd | Construction | 2015 |
| A Stewart Consulting Ltd | Information & communication | 2018 |
| A&A PV Consulting Limited | Professional & scientific | 2016 |
| A&M Investment Holdings Ltd | Real estate | 2023 |
| A&M Transport & Recycling Limited | Water & waste | 2003 |
| A-Star (South) Limited | Energy | 2014 |
| A. & a. King (Property Investments) Ltd | Real estate | 2007 |
| A. & a. King Limited | Extraterritorial | 1989 |
| A. Bergen Consulting Limited | Professional & scientific | 2020 |
| A. Panarese Consultants Limited | Health & social care | 2011 |
| A.D.H. Electrical Ltd | Construction | 2003 |
| A.H. Harvey & Sons Limited | Construction | 1999 |
| A.W. Golf Limited | Information & communication | 2014 |
| A1 Aggregates Limited | Wholesale & retail | 2022 |
| A1 Budget Skips Ltd | Water & waste | 2007 |
| A1 Office Furniture Limited | Wholesale & retail | 2013 |
| A2Z King Art and Design Ltd | Wholesale & retail | 2022 |
| A3K Properties Limited | Real estate | 2020 |
| A3R Ventures Private Limited | Real estate | 2024 |
| AAA Minds Limited | Information & communication | 2018 |
| Aalto Consulting Limited | Information & communication | 2024 |
| AAM Software Limited | Information & communication | 2020 |
| Aamg UK Ltd | Administrative & support | 2022 |
| Aamir Group Enterprises Ltd | Information & communication | 2018 |
| Aangels Care Ltd | Health & social care | 2026 |
| Aarc Contracting Ltd | Information & communication | 2023 |
| Aarc Holdings Ltd | Financial services | 2023 |
| Aarc Residentials Ltd | Real estate | 2023 |
| Aardun Limited | Professional & scientific | 2021 |
| Aardvark Accounting Ltd | Professional & scientific | 2016 |
| Aardvark Creative Ltd | Professional & scientific | 2026 |
| Aarepairs Limited | Wholesale & retail | 2025 |
| Aask Consulting Ltd | Information & communication | 2017 |
| AB Digital Consultancy Ltd | Information & communication | 2023 |
| AB Forensic Accounting Services Limited | Professional & scientific | 2019 |
| Abacus Home Wessex Limited | Construction | 2019 |
| Abal Mckey Limited | Professional & scientific | 2018 |
| Abbey Business Centre Limited | Real estate | 2019 |
| Abbey Hill Medical Limited | Professional & scientific | 2018 |
| ABC (Allison Bayani Consulting) Limited | Information & communication | 2026 |
| Above and Beyond Medics Limited | Health & social care | 2016 |
| Above Digital Limited | Information & communication | 2010 |
| ABS Computer Systems Ltd | Information & communication | 1991 |
| Absnt Technologies Ltd | Information & communication | 2026 |
| Absolute Developments Building and Design Ltd | Construction | 2021 |
| Absolute Motion Limited | Information & communication | 2010 |
| Abstract Studio Partners Ltd | Professional & scientific | 2021 |
| AC Analytics Limited | Information & communication | 2020 |
| Accelerate Evolution Management Consulting Limited | Professional & scientific | 2024 |
| Accelion Ltd | Information & communication | 2026 |
| Accentuate Holdings Limited | Financial services | 2015 |
| Access Commercial Ltd | Financial services | 2013 |
| Access Lifts Limited | Construction | 1996 |
| Accessible Accounting Limited | Financial services | 2018 |
| Accountful Limited | Professional & scientific | 2023 |
| Accustar Limited | Professional & scientific | 2024 |
| Ace Retail Ventured Ltd | Wholesale & retail | 2025 |
| Ace Sustainable Futures Limited | Professional & scientific | 2024 |
| Ace Welding Structures Limited | Construction | 2020 |
| Acordos Properties Ltd | Real estate | 2018 |
| Acorn Group Management Ltd | Financial services | 2022 |
| Acorn Passive Fire Protection Ltd | Professional & scientific | 2023 |
| Acorn Plastering Contractors Limited | Construction | 2010 |
| Acquirepremises Ltd | Information & communication | 2013 |
| Acrestate Private Limited | Real estate | 2021 |
| Acrobat Trustees Ltd | Financial services | 2024 |
| Actio Recruitment Limited | Administrative & support | 2022 |
| Action Station 5 Limited | Real estate | 2024 |
| Active Paddling Ltd. | Arts & recreation | 2017 |
| Active Publishing Limited | Information & communication | 2003 |
| Active Root Nutrition Ltd | Administrative & support | 2024 |
| Activebacks Ltd | Health & social care | 2011 |
| Actu@Te Ltd | Professional & scientific | 2015 |
| Actua Risk Limited | Administrative & support | 2003 |
| Actuverse Ltd | Financial services | 2024 |
| Acuitas Communications Ltd | Professional & scientific | 2015 |
| Acvlt Limited | Professional & scientific | 2024 |
| ADA Business Solutions Ltd | Other services | 2012 |
| Adam J. Meldan Limited | Construction | 1973 |
| Adam Smith Research Consulting Ltd | Professional & scientific | 2026 |
| Adam's Web Services Limited | Information & communication | 2019 |
| Adamant Digital Limited | Information & communication | 2025 |
| Adapt Freelancer Limited | Information & communication | 2018 |
| Adaptation Station Ltd | Other services | 2011 |
| Adaptiv Mobility Ltd | Wholesale & retail | 2021 |
| Adaptiv Property Ltd | Real estate | 2025 |
| ADD Capital Finance Limited | Financial services | 2005 |
| ADD Heat Ltd | Construction | 2025 |
| ADD.4PROPERTY Ltd | Real estate | 2017 |
| Added Vision Limited | Financial services | 2020 |
| Adderley Network Consulting Ltd | Information & communication | 2014 |