| Athena Forte Ltd | Wholesale & retail | 2023 |
| Athena Gesda Ltd | Professional & scientific | 2026 |
| Athena Nottingham Limited | Real estate | 2023 |
| Athena Transformation Limited | Professional & scientific | 2023 |
| Athi-Sihle Limited | Health & social care | 2016 |
| Athletic Academy CIC | Education | 2025 |
| Athletic Movement Ltd | Wholesale & retail | 2020 |
| Athlevo Ltd | Health & social care | 2025 |
| Athmac Holdings Limited | Construction | 2025 |
| Atholl House Residents Company Limited | Real estate | 2009 |
| Atia K9 Security Limited | Administrative & support | 2024 |
| Atilgan Limited | Hospitality | 2023 |
| Atilinic Ltd | Transport & logistics | 2020 |
| Atim Consulting Ltd | Other services | 2015 |
| ATIMES2 Limited | Hospitality | 2008 |
| Atis IT Consultancy PVT Ltd | Information & communication | 2007 |
| Atjb Services Limited | Manufacturing | 2022 |
| ATK Goody's Ltd | Hospitality | 2025 |
| ATK Pops Ltd | Hospitality | 2026 |
| Atka Ltd | Transport & logistics | 2023 |
| Atkins Residential Ltd | Real estate | 2022 |
| Atkinson & Affiliates Ltd | Professional & scientific | 2013 |
| Atkinsons Engineering Ltd | Professional & scientific | 2023 |
| ATL Building Services Limited | Construction | 2018 |
| ATL Luggage Ltd | Wholesale & retail | 2024 |
| ATL Payments Limited | Administrative & support | 2011 |
| ATL Security Holdings Ltd | Administrative & support | 2011 |
| Atlantic Fish Bar (Tamworth) Limited | Hospitality | 2024 |
| Atlantic Services & Supplies Ltd | Wholesale & retail | 2017 |
| Atlantis Land Developments Limited | Construction | 2003 |
| Atlas Business Centre Ltd | Real estate | 2012 |
| Atlas Electricals Nottingham Ltd | Construction | 2021 |
| Atlas Fine Wines Limited | Wholesale & retail | 2010 |
| Atlas Group Service Ltd | Construction | 2024 |
| Atlas Home Nottingham Ltd | Construction | 2026 |
| Atlas LES Ltd | Administrative & support | 2019 |
| Atlas Renewable Energy Solutions Limited | Professional & scientific | 2010 |
| Atlas School of Training Ltd | Education | 2022 |
| Atlas Testing Services Ltd. | Information & communication | 2015 |
| Atlas View Limited | Professional & scientific | 2026 |
| Atlas Worldwide Trading Ltd | Wholesale & retail | 2020 |
| ATM Lead Generation Limited | Professional & scientific | 2026 |
| ATM Window Cleaning Ltd | Administrative & support | 2018 |
| Atma Skin Ltd | Other services | 2026 |
| Atmiya Enterprise Ltd | Wholesale & retail | 2019 |
| Atmos Atelier Ltd | Wholesale & retail | 2025 |
| Atmos Vapes Limited | Wholesale & retail | 2018 |
| ATO Travel N Shipping Consultancy Ltd | Administrative & support | 2025 |
| Atom Landscapes Ltd | Administrative & support | 2026 |
| Atom Machines Limited | Manufacturing | 2025 |
| Atom Solutions (Environmental) Limited | Professional & scientific | 2008 |
| Atom Ventures 2 Limited | Hospitality | 2023 |
| Atom Ventures Ltd | Hospitality | 2017 |
| Atomic (UK) Limited | Real estate | 2001 |
| Atomic Consultancy Ltd | Professional & scientific | 2021 |
| Atomic EOT Limited | Financial services | 2023 |
| Atomic MC Limited | Financial services | 2015 |
| Atomic Multimedia Consultants Limited | Information & communication | 1998 |
| Atos Medical UK Limited | Wholesale & retail | 2001 |
| ATP Creative Ltd | Professional & scientific | 2025 |
| Atpaas Limited | Information & communication | 2016 |
| Atrium & Facade Consultancy Ltd | Professional & scientific | 2023 |
| Atrium Developments Limited | Construction | 2007 |
| ATT Group Limited | Administrative & support | 2019 |
| Attach Patch Ltd | Health & social care | 2023 |
| Attam Limited | Extraterritorial | 2008 |
| Attenborough Brush Limited | Manufacturing | 2000 |
| Attenborough Dental Laboratories Ltd | Manufacturing | 2000 |
| Attenborough Direct Ltd | Manufacturing | 2001 |
| Attenborough Heating Services Limited | Construction | 2013 |
| Attenborough Industrial Doors Limited | Financial services | 1997 |
| Attenborough Limited | Manufacturing | 1935 |
| Attenborough Medical Limited | Manufacturing | 2021 |
| Attenborough Software Limited | Information & communication | 1994 |
| Attento Security Solutions Ltd | Administrative & support | 2026 |
| Attero Projects Limited | Water & waste | 2017 |
| Attic Theatre School Ltd | Arts & recreation | 2021 |
| Atticus Building and Construction Ltd | Construction | 2020 |
| Attilas Group Ltd | Hospitality | 2024 |
| Attlock PUB Co Ltd | Hospitality | 2021 |
| Attmo Ltd | Health & social care | 2022 |
| Attract Limited | Information & communication | 2019 |
| Attributed Marketing Ltd | Professional & scientific | 2023 |
| Attuned Psychology and Consulting Ltd | Education | 2026 |
| Attur Sound and Production Ltd | Manufacturing | 2023 |
| ATU Consultants Limited | Information & communication | 2017 |
| ATW Ltd | Administrative & support | 2015 |
| ATW Signs Limited | Construction | 2020 |
| ATW Travel Marketing Ltd | Administrative & support | 2015 |
| AU Executives Ltd | Wholesale & retail | 2023 |
| AU Fait Consultancy Limited | Professional & scientific | 2003 |
| AU Private Ltd | Wholesale & retail | 2024 |
| Aubd Limited | Information & communication | 2007 |
| Aubea Limited | Professional & scientific | 2025 |
| Aubergine IT Consultants Ltd | Information & communication | 2015 |
| Auction Estates Limited | Real estate | 2016 |
| Audacity Leisure Ltd | Hospitality | 2010 |
| Audio Boost Ltd | Administrative & support | 2018 |
| Audio Electrical Limited | Wholesale & retail | 2007 |
| Audio Integer Limited | Arts & recreation | 2000 |