| Arba Regeneration (Mansfield) Limited | Construction | 2017 |
| Arbar Ltd | Extraterritorial | 2025 |
| Arbor Tree Services Limited | Construction | 2022 |
| ARC Notts Limited | Professional & scientific | 2025 |
| Arc-Lite Ltd | Construction | 2023 |
| Arcadesystems Ltd | Wholesale & retail | 2018 |
| Arcanore Ltd | Information & communication | 2025 |
| Archie Properties Limited | Real estate | 2026 |
| Archie's Plumbing and Tiling Ltd | Construction | 2021 |
| Argent Brokers Limited | Wholesale & retail | 2013 |
| Argestes Ltd | Real estate | 2024 |
| Arigatou Consulting Limited | Professional & scientific | 2013 |
| ARJ Solutions Ltd | Wholesale & retail | 2025 |
| ARK Living LLP | | 2018 |
| ARK Measurement and Control Limited | Construction | 2001 |
| ARK Vehicles Limited | Wholesale & retail | 2026 |
| ARL Partners Global Ltd | Professional & scientific | 2025 |
| Arla Construction Ltd | Construction | 2024 |
| Armada Active Limited | Wholesale & retail | 2026 |
| Arromax Structures Limited | Manufacturing | 1988 |
| Arrow Builders Merchants (North Notts.) Limited | Extraterritorial | 1983 |
| Arrowdale Building Services Limited | Construction | 2012 |
| ARS - Asset Recovery Solutions Limited | Information & communication | 2019 |
| Art Engineering Services Ltd | Professional & scientific | 2017 |
| Art Express Ltd | Transport & logistics | 2017 |
| Arthur Flury UK Limited | Wholesale & retail | 2010 |
| Artop & Co Ltd | Professional & scientific | 2004 |
| Artur Wiktor Limited | Transport & logistics | 2024 |
| Arwa Ltd | Hospitality | 2020 |
| Aryav Ltd | Wholesale & retail | 2020 |
| Asai Dosa Ltd | Hospitality | 2026 |
| Asbestos Compliance Solutions Limited | Construction | 2013 |
| Asbestos GRP Labs Ltd | Other services | 2018 |
| ASC Hair Limited | Other services | 2021 |
| Ascent Business Advisory Ltd | Professional & scientific | 2026 |
| Ascot Pianos Ltd | Wholesale & retail | 2020 |
| ASD Contracting Mansfield Ltd | Construction | 2024 |
| Asgaad Limited | Information & communication | 2023 |
| ASH Catering Services Limited | Hospitality | 2015 |
| ASH PVT Limited | Administrative & support | 2018 |
| Ashdown Creations Limited | Construction | 2020 |
| Ashfield Brake Calipers Ltd | Wholesale & retail | 2013 |
| Ashfield Park Homes Ltd | Hospitality | 2021 |
| Ashfield Steel Limited | Wholesale & retail | 2018 |
| Ashfielddrops Ltd | Wholesale & retail | 2024 |
| Ashk North West Limited | Wholesale & retail | 2015 |
| Ashleigh Gardens Management Company Limited | Households | 2007 |
| Ashley Bellamy Furnishing Ltd | Wholesale & retail | 1996 |
| Ashlo Construction Consultants Ltd | Construction | 2022 |
| Ashlo Living Limited | Construction | 2024 |
| ASK (LA) Ltd | Health & social care | 2025 |
| ASK Heating & Maintenance Ltd | Construction | 2021 |
| ASK News Limited | Wholesale & retail | 2012 |
| ASK Nottingham Limited | Hospitality | 2025 |
| ASK Property (Notts) Limited | Real estate | 2025 |
| ASK Property Ltd | Real estate | 2018 |
| ASK2GLOBAL Ltd | Administrative & support | 2025 |
| Askara Ltd | Transport & logistics | 2017 |
| Askjd Properties Ltd | Real estate | 2024 |
| Asma’S Shine Limited | Administrative & support | 2025 |
| Asmech Systems Holdings Limited | Other services | 2024 |
| Asmech Systems Limited | Manufacturing | 1998 |
| Aspell Investments Ltd | Financial services | 2018 |
| Aspen Park Holdings Ltd | Hospitality | 2024 |
| Aspire Home Group Limited | Real estate | 2022 |
| Asra Engineering Services Ltd | Professional & scientific | 2024 |
| Assist IT LLP | | 2023 |
| Associated Heating Services Ltd | Construction | 2019 |
| Association of Competent Person Schemes Limited | Extraterritorial | 2012 |
| Asta Property Maintenance Ltd | Construction | 2019 |
| Astha Limited | Health & social care | 2003 |
| Astor Commercial Ltd | Real estate | 2005 |
| AT Model Engineering Limited | Professional & scientific | 2022 |
| AT My Place.Com Limited | Administrative & support | 2008 |
| Atay Decorations Ltd | Construction | 2021 |
| Athena 9 Ltd | Professional & scientific | 2011 |
| Athena Educational Consult Ltd | Extraterritorial | 2022 |
| Athens G Ltd | Hospitality | 2025 |
| ATK Plastering Limited | Construction | 2011 |
| Atkin & SON Limited | Extraterritorial | 2017 |
| ATM Partnership Ltd | Hospitality | 2024 |
| Atom IT Solutions Ltd | Information & communication | 2013 |
| Atomic Construction Ltd | Construction | 2025 |
| Attabros Ltd | Wholesale & retail | 2025 |
| Attwood Medical Services Limited | Education | 2019 |
| Aumecon Limited | Manufacturing | 2006 |
| Aumshiv Development Property Letting Limited | Real estate | 2025 |
| Aunty Sues Day Care Limited | Other services | 2016 |
| Aura Supported Living Ltd | Health & social care | 2020 |
| Aurora Networks Limited | Information & communication | 2021 |
| Autism and Neurodiversity Coaching Limited | Public administration | 2023 |
| Auto 200 Limited | Wholesale & retail | 2017 |
| Auto Door Solutions Limited | Professional & scientific | 2010 |
| Auto Refinishers Limited | Extraterritorial | 1991 |
| Autocentre (U.K.) Limited | Wholesale & retail | 1998 |
| Automated Works Limited | Manufacturing | 2021 |
| Automotive Lift Services Ltd | Manufacturing | 2014 |
| Available Taxi Hire Limited | Administrative & support | 2019 |
| Avalon (Mansfield) Management Company Limited | Households | 2018 |
| Avalon Autos Limited | Wholesale & retail | 2012 |