| Accu-Set Limited | Health & social care | 2013 |
| Ace Assessments Ltd | Health & social care | 2018 |
| Ace Contract Furniture Limited | Manufacturing | 2023 |
| Aced Care Services Ltd | Health & social care | 2024 |
| Acel Constructions Ltd | Construction | 2018 |
| ACF Group Holdings Limited | Financial services | 2024 |
| ACF Home Cover Limited | Other services | 2025 |
| ACF Homecare Limited | Other services | 2024 |
| ACF Plumbing and Heating Limited | Construction | 2017 |
| ACF Property Group Limited | Real estate | 2018 |
| Acgbcn Limited | Health & social care | 2014 |
| ACM Trans Courier Ltd | Transport & logistics | 2023 |
| ACM Welding Services Limited | Manufacturing | 2015 |
| Acquaint Consolidated Holdings Limited | Administrative & support | 2023 |
| Acquaint Consolidated Services Limited | Administrative & support | 2006 |
| Acquired Goods Ltd | Wholesale & retail | 2025 |
| Acredale Developments Limited | Construction | 2026 |
| Acres Information Technology Services Ltd | Information & communication | 2020 |
| Acrylic Fabrications Limited | Manufacturing | 2006 |
| Actinica Limited | Construction | 2025 |
| Activan Ltd | Transport & logistics | 2015 |
| Active Supported Living Limited | Health & social care | 2022 |
| Actnow Mortgages Ltd | Financial services | 2021 |
| Acts 2:42 Ministries | Other services | 2008 |
| Acuity Engineering Limited | Professional & scientific | 2023 |
| AD Property Atelier Ltd | Construction | 2026 |
| Adam & Sons Drive Ltd | Transport & logistics | 2025 |
| Adam Elliotts Properties Limited | Construction | 2023 |
| Adam Green Grocer Ltd | Wholesale & retail | 2022 |
| Adam.Zdunek Transport Ltd | Transport & logistics | 2025 |
| Adams Investments Limited | Financial services | 1922 |
| Adams of Northampton Limited | Real estate | 1963 |
| Adasam Limited | Information & communication | 2001 |
| ADB Transport Ltd | Transport & logistics | 2026 |
| Adedoja Limited | Health & social care | 2019 |
| Adek Repairs Limited | Wholesale & retail | 2024 |
| Adela Cleaning Corby Ltd | Administrative & support | 2026 |
| Ades Logistics Ltd | Transport & logistics | 2023 |
| ADI & Magi Trans Ltd | Transport & logistics | 2013 |
| Adidi Ltd | Transport & logistics | 2021 |
| Adlan Accountants Limited | Professional & scientific | 2021 |
| ADM Moving Ltd | Transport & logistics | 2026 |
| Admag (Dagwood) Ltd | Real estate | 2013 |
| Admedien Limited | Information & communication | 2021 |
| ADN Living Ltd | Health & social care | 2018 |
| ADR Trans Ltd | Manufacturing | 2019 |
| Adrenaline Alley | Arts & recreation | 2006 |
| Adria Foods Ltd | Wholesale & retail | 2015 |
| Adrian Bell Golf Limited | Wholesale & retail | 2009 |
| Adrian Kostyra Ltd | Wholesale & retail | 2024 |
| Adrian's Motors Ltd | Manufacturing | 2019 |
| ADS Contracting Ltd | Professional & scientific | 2015 |
| ADS Engineering Solutions Ltd | Professional & scientific | 2026 |
| ADS NO. 1 Ltd | Professional & scientific | 2021 |
| ADS NO. 2 Ltd | Professional & scientific | 2021 |
| ADS NO. 4 Ltd | Professional & scientific | 2021 |
| Adsj Real Estate Limited | Professional & scientific | 2022 |
| ADV Trans Ltd | Transport & logistics | 2015 |
| Advance Auto Car Ltd | Wholesale & retail | 2026 |
| Advanced Heat Limited | Construction | 2020 |
| Advocitude Ltd | Administrative & support | 2024 |
| ADY Quick Smart Repairs Ltd | Wholesale & retail | 2022 |
| AE Machinery Limited | Transport & logistics | 2023 |
| AEA Power Ltd | Transport & logistics | 2014 |
| Aegimuta Limited | Wholesale & retail | 2026 |
| AEM Auto Ltd | Wholesale & retail | 2025 |
| AEN Drylining Ltd | Construction | 2026 |
| Aepos UK Ltd | Extraterritorial | 2021 |
| Aeroponic Systems Limited | Agriculture & fishing | 2012 |
| Aeroworx Ltd | Professional & scientific | 2019 |
| AF Building & Maintenance Ltd | Construction | 2015 |
| Affable Accountancy Limited | Professional & scientific | 2026 |
| Affinity (UK) Limited | Professional & scientific | 2011 |
| Afisjo Ltd | Health & social care | 2024 |
| AFP Limited | Real estate | 2005 |
| Africa-Bettar Ltd | Health & social care | 2019 |
| Africonti Logistics Ltd | Transport & logistics | 2022 |
| Afriher Ltd | Professional & scientific | 2026 |
| Afrinity Productions Ltd | Professional & scientific | 2020 |
| AG Clark Group Limited | Financial services | 2026 |
| AG Fixers Limited | Construction | 2023 |
| AG Security ALL Services Ltd | Financial services | 2022 |
| Aga-Robotics Limited | Manufacturing | 2024 |
| Agency Care Staff Ltd | Professional & scientific | 2021 |
| Agenda Partnership Limited | Administrative & support | 2014 |
| Agilsafe Partners Ltd | Professional & scientific | 2025 |
| Agkiya Limited | Information & communication | 2019 |
| Aglm Ltd | Wholesale & retail | 2026 |
| Agrigoroaie Delivery Services Ltd | Transport & logistics | 2026 |
| Agrigoroaiei.Ltd.Ro Ltd | Transport & logistics | 2026 |
| AI IT Today Ltd | Information & communication | 2025 |
| AI Pro Investments Ltd | Real estate | 2025 |
| AI Thunder Limited | Information & communication | 2026 |
| Aircare (Corby) Limited | Administrative & support | 2002 |
| Aircare Compressor Services Limited | Manufacturing | 1991 |
| Airfield Training Company Limited | Professional & scientific | 2018 |
| Airs Kerblayers Limited | Construction | 2025 |
| Aist Ltd | Transport & logistics | 2021 |
| Aitop Healthcare Limited | Health & social care | 2016 |
| Aixhumans Ltd | Professional & scientific | 2025 |