| ADV Lendco UK Limited | Financial services | 2022 |
| Advance Xtra Ltd | Professional & scientific | 2011 |
| Advanced Air Hygiene Ltd | Construction | 1996 |
| Advanced Biotechnologies Limited | Manufacturing | 1989 |
| Advanced Pest Control Limited | Administrative & support | 2000 |
| Advanced Xtracts Ltd | Manufacturing | 2018 |
| Advances Against Aspergillosis Ltd | Education | 2022 |
| Advantage Projects Limited | Professional & scientific | 2015 |
| Advention Consulting Limited | Professional & scientific | 2023 |
| Adventure IS Ours C.I.C. | Education | 2025 |
| Adventures Begin Ltd | Professional & scientific | 2018 |
| Advia Therapeutics UK Limited | Professional & scientific | 2024 |
| Advisertech Ltd | Information & communication | 2019 |
| Advocating Together Ltd | Other services | 2025 |
| Advorto UK Limited | Information & communication | 2010 |
| Adwin Tech Ltd | Information & communication | 2025 |
| ADX Electrical Limited | Construction | 2026 |
| AE BIA Assessments Limited | Administrative & support | 2016 |
| AEJ Pro Ltd | Professional & scientific | 2023 |
| AEL - Limassol Limited | Administrative & support | 2015 |
| Aenigma Solutions Ltd | Construction | 2022 |
| Aequitas Estate Management Limited | Real estate | 2021 |
| AER Testing Solutions Limited | Professional & scientific | 2022 |
| Aerospace Reliance Limited | Administrative & support | 2017 |
| Aerospheres (UK) Limited | Wholesale & retail | 1990 |
| Aerovect UK Limited | Information & communication | 2026 |
| Aesa Group Limited | Administrative & support | 2025 |
| Aesop Bidco Limited | Financial services | 2024 |
| Aesop Holdco Limited | Financial services | 2024 |
| Aesthetica Medical (Cheshire) Ltd | Health & social care | 2016 |
| Aeva Medical Ltd | Health & social care | 2025 |
| AF Active Limited | Professional & scientific | 2018 |
| AF Group Holdings Limited | Financial services | 2023 |
| AF24 Ltd | Health & social care | 2022 |
| Afast Aero Limited | Manufacturing | 2018 |
| Affable Enterprises Limited | Wholesale & retail | 2020 |
| Afford Ability Limited | Professional & scientific | 2025 |
| Affymetrix, UK Ltd. | Administrative & support | 1998 |
| Afinno Solutions Limited | Professional & scientific | 2024 |
| AFK Executive Ltd | Financial services | 2026 |
| AFN Rentals Limited | Real estate | 2019 |
| Aforza Limited | Information & communication | 2019 |
| AFS Biomass Ltd | Manufacturing | 2012 |
| After Web DEV Ltd | Administrative & support | 2026 |
| Afterpark Limited | Households | 1989 |
| Afyx Therapeutics UK Ltd. | Wholesale & retail | 2024 |
| AG Global Ltd | Wholesale & retail | 2020 |
| AGA Mortlock Photography Ltd | Professional & scientific | 2019 |
| Agass Holdings Ltd | Financial services | 2020 |
| AGC Aerospheres Holdings Limited | Wholesale & retail | 2015 |
| AGE Friendly Culture CIC | Education | 2025 |
| Ageha Conseil Ltd | Information & communication | 2020 |
| Agemo AI Ltd | Information & communication | 2023 |
| Agency Consultancy Services Limited | Professional & scientific | 2020 |
| Agentlease Ltd | Manufacturing | 2026 |
| Aggyabode Limited | Real estate | 2021 |
| Aggytech Consultancy Services Limited | Administrative & support | 2017 |
| Aghoco 1442 Limited | Real estate | 2016 |
| Aghoco 1630 Limited | Extraterritorial | 2017 |
| Agile Cohort Limited | Professional & scientific | 2021 |
| Agilearc Limited | Administrative & support | 2025 |
| Agilepath Genius Limited | Information & communication | 2025 |
| Agilesource Limited | Information & communication | 2025 |
| Agkn Property Investments Ltd | Real estate | 2022 |
| Agon Gaming Ltd | Professional & scientific | 2019 |
| Agouti Limited | Information & communication | 2025 |
| Agriaccel Limited | Professional & scientific | 2025 |
| AH ALI Ltd | Health & social care | 2019 |
| AH Import and Export Limited | Wholesale & retail | 2021 |
| AH Project (UK) Ltd | Professional & scientific | 2014 |
| AHA Housing Limited | Real estate | 2022 |
| Ahead DB UK Limited | Wholesale & retail | 2023 |
| Aherne Brothers Limited | Real estate | 2012 |
| Aheto Professional Services Limited | Professional & scientific | 2023 |
| Ahfs Holdings Limited | Financial services | 2013 |
| Ahmed Kais Ltd | Real estate | 2023 |
| AHR Retail Ltd | Hospitality | 2025 |
| Ahsl Healthcare Ltd | Health & social care | 2017 |
| AI Interims Limited | Administrative & support | 2025 |
| AI Perfect Ltd | Other services | 2025 |
| AI Side Quest Limited | Information & communication | 2026 |
| AI Tech Xperts Ltd | Information & communication | 2025 |
| AIA Data Solutions Limited | Professional & scientific | 2026 |
| Aifos Limited | Professional & scientific | 2025 |
| Ailogica Limited | Other services | 2016 |
| AIM 4 Hope CIC | Education | 2022 |
| AIM Academy Limited | Administrative & support | 1994 |
| AIM Commercial Limited | Professional & scientific | 2024 |
| AIM High Cheshire Ltd | Arts & recreation | 2024 |
| AIM Imports Ltd | Wholesale & retail | 2020 |
| Aimee Balcombe Limited | Professional & scientific | 2022 |
| Aiming Limited | Real estate | 2021 |
| Aimée B Beauty Aesthetics Limited | Other services | 2019 |
| Aina Consulting Ltd | Administrative & support | 2013 |
| Ainsworth Property Assets Limited | Real estate | 2016 |
| Aintree Plastics (Holdings) Limited | Professional & scientific | 2016 |
| Ainur Limited | Administrative & support | 2025 |
| Aionex Technologies Ltd. | Information & communication | 2024 |
| Air Consultancy Ltd | Transport & logistics | 2016 |
| Air Control Concepts European Holdings Ltd | Wholesale & retail | 2025 |