| Anish IT Services Limited | Information & communication | 2024 |
| Anita Ayoola Health Ltd | Health & social care | 2025 |
| Anju Logistics Limited | Transport & logistics | 2022 |
| Anlaby Road Management Limited | Extraterritorial | 2016 |
| ANN Barthorpe Limited | Health & social care | 2023 |
| ANN Holmwood Ltd | Health & social care | 2023 |
| Anne Burton Limited | Professional & scientific | 2013 |
| Annesley Harris Ltd | Professional & scientific | 2019 |
| Annuity Advisers Limited | Professional & scientific | 2002 |
| Antcliff Mortgages & Protection Ltd | Financial services | 2016 |
| Antelope Interiors Ltd | Professional & scientific | 2011 |
| Antiaccident Limited | Professional & scientific | 2023 |
| Antony Fawbert Limited | Professional & scientific | 2013 |
| Anu's Grab 'a' Bite Ltd | Hospitality | 2026 |
| Anxietystop Limited | Professional & scientific | 2025 |
| Anze Limited | Manufacturing | 2019 |
| Aogl Limited | Construction | 2024 |
| AP Contracting (Chesterfield) Limited | Construction | 2015 |
| AP Mortgage Solutions Ltd | Financial services | 2019 |
| Apartment (Chesterfield) Limited | Hospitality | 2015 |
| APC Electrical Engineers Ltd | Construction | 2006 |
| Apex Enterprises (Europe) Limited | Administrative & support | 2003 |
| Apex Home Rentals Ltd | Real estate | 2024 |
| Apex Industrial Coatings Ltd | Manufacturing | 2021 |
| Apex Physiotherapy Mansfield Ltd | Health & social care | 2024 |
| APG Security Solutions Limited | Administrative & support | 2014 |
| APH Property Investment Ltd | Real estate | 2025 |
| API Tech Smart Solutions Ltd | Manufacturing | 2019 |
| Aplus Medical Services & Training Ltd | Education | 2022 |
| Aplus Security Services & Training Ltd | Administrative & support | 2023 |
| Apollo Distribution Solutions (Doncaster) Limited | Transport & logistics | 2004 |
| Appaaro Investments One Limited | Financial services | 2026 |
| Appleby Property Management Limited | Professional & scientific | 2003 |
| Applegarth Day Nurseries Limited | Education | 2004 |
| Applied Pumps Ltd | Wholesale & retail | 2000 |
| Applied Service Management Global Limited | Information & communication | 2000 |
| Appnin Group Ltd | Other services | 2016 |
| Apprentice Team Ltd | Education | 2013 |
| Approved Business Communications Limited | Information & communication | 2015 |
| Appy Diner Ltd | Information & communication | 2020 |
| APS GB Limited | Manufacturing | 2009 |
| Apsele Properties Ltd | Real estate | 2022 |
| Aptus Environmental & Electrical Control Ltd | Construction | 2025 |
| Aptus Home Improvements Limited | Construction | 2007 |
| Aptus Plumbing & Heating Limited | Extraterritorial | 2013 |
| APW Heating and Building Services Ltd | Construction | 2020 |
| AQ Media Services Limited | Information & communication | 2020 |
| AQG Traders Ltd | Administrative & support | 2022 |
| Aqua Drainage Solutions Limited | Water & waste | 2021 |
| Aqua Plumbing & Heating Solutions Ltd | Construction | 2019 |
| Aquadabra Ltd | Hospitality | 2018 |
| Aquaheat PH Ltd | Construction | 2014 |
| Aquarium Limited | Agriculture & fishing | 2024 |
| Aquila Minerals Limited | Professional & scientific | 2015 |
| ARB Access Group Limited | Administrative & support | 2012 |
| Arborlow Limited | Construction | 2024 |
| ARC Engineering and Management Limited | Professional & scientific | 2026 |
| ARC Occupational Health Limited | Health & social care | 2025 |
| ARC Retail Technology Limited | Information & communication | 2026 |
| Arcashar Limited | Hospitality | 2019 |
| Architectural Metal and Glass Ltd | Manufacturing | 2019 |
| ARD Construction Ltd | Construction | 2013 |
| Ardane Limited | Real estate | 2003 |
| Arden Coffee Sales Limited | Wholesale & retail | 2009 |
| Area 51 Martial Arts & Tricking Academy CIC | Education | 2020 |
| Ariel Plastics Limited | Manufacturing | 1988 |
| Aristocat Holdings Ltd | Hospitality | 2022 |
| ARK Sales and Promotions Ltd | Real estate | 2018 |
| ARK Specialist Healthcare LLP | | 2011 |
| Arker Therapies Ltd | Health & social care | 2026 |
| Arkouda Property Limited | Real estate | 2021 |
| Arkwright Consultancy Ltd | Administrative & support | 2025 |
| Arkwright Consulting Ltd | Professional & scientific | 2026 |
| Arkwright Miners Welfare Social Club Limited | Hospitality | 2003 |
| Armco Group Limited | Construction | 2025 |
| Armoto Ltd | Manufacturing | 2015 |
| Armour Plated Handbags Limited | Wholesale & retail | 2019 |
| Armstrong Contracts (Chesterfield) Limited | Transport & logistics | 1988 |
| Arnze Limited | Information & communication | 2019 |
| ARO Valeting Centre Ltd | Wholesale & retail | 2025 |
| ARR Rail Solutions Ltd | Professional & scientific | 2013 |
| Arrow Butler Castings Limited | Manufacturing | 1989 |
| Arsha Holdings Limited | Financial services | 2026 |
| Art Avens Care Limited | Health & social care | 2019 |
| Arte Nova Beauty Ltd | Other services | 2022 |
| Artisan (UK) Developments Limited | Construction | 1994 |
| Artisan (UK) Land Limited | Construction | 2016 |
| Artisan (UK) PLC | Professional & scientific | 1998 |
| Artisan (UK) Projects Limited | Construction | 2000 |
| Artisan (UK) Properties Limited | Real estate | 1999 |
| Artisan Contracting Limited | Construction | 1997 |
| Artisan Financial Limited | Financial services | 2015 |
| Artisan Mortgages Limited | Financial services | 2023 |
| Artizan Baits Ltd | Wholesale & retail | 2025 |
| Arundel Hair & Beauty Ltd | Other services | 2025 |
| Arya Sharif Ltd | Hospitality | 2020 |
| Aryal's Catering Limited | Hospitality | 2024 |
| AS Local Express Ltd | Wholesale & retail | 2026 |
| AS Luxury Estates Ltd | Real estate | 2026 |
| ASB Business Services (UK) Limited | Professional & scientific | 2008 |