| Atlantic Seastar LP | | 2014 |
| Atlantic Supplies L.P. | | 2011 |
| Atlantic Trade LP | | 2015 |
| Atlantic Wall LP | | 2016 |
| Atlantic Yacht Management LP | | 2014 |
| Atlantics Apartments Ltd | Hospitality | 2023 |
| Atlantime Ventures LP | | 2015 |
| Atlantis Resources (Scotland) Limited | Administrative & support | 2008 |
| Atlantus L.P. | | 2016 |
| Atlas 13 Limited | Wholesale & retail | 2023 |
| Atlas 365 Solutions Ltd | Construction | 2022 |
| Atlas Alliance LP | | 2014 |
| Atlas Business Corporation L.P. | | 2011 |
| Atlas Commerce L.P. | | 2016 |
| Atlas Company Services LP | | 2016 |
| Atlas Corporation L.P. | | 2012 |
| Atlas Endurance Limited | Manufacturing | 2018 |
| Atlas Europe L.P. | | 2010 |
| Atlas Gifts Limited | Wholesale & retail | 2022 |
| Atlas Global Services L.P. | | 2012 |
| Atlas Hotels (Cambridge) Limited | Hospitality | 2002 |
| Atlas Hotels (Edinburgh Waterfront) Limited | Hospitality | 1997 |
| Atlas Hotels (Glasgow Airport) Limited | Hospitality | 1997 |
| Atlas Hotels (Hemel Hempstead) Limited | Hospitality | 2002 |
| Atlas Hotels (Luton Airport) Limited | Hospitality | 2000 |
| Atlas Hotels (Stirling) Limited | Hospitality | 1995 |
| Atlas Import/Export L.P. | | 2011 |
| Atlas Innovations LP | | 2016 |
| Atlas International Service Solutions LP | | 2016 |
| Atlas Merchants L.P. | | 2008 |
| Atlas Mile Ltd | Transport & logistics | 2026 |
| Atlas Offshore Consult Limited | Professional & scientific | 2018 |
| Atlas Organisation L.P. | | 2013 |
| Atlas Physiotherapy Edinburgh Ltd | Health & social care | 2025 |
| Atlas Processing Limited | Manufacturing | 2025 |
| Atlas Sales LP | | 2014 |
| Atlas Shipping and Logistics Company Ltd | Other services | 2018 |
| Atlas Stratton LP | | 2016 |
| Atlas Total Solutions L.P. | | 2011 |
| Atlas Trading LP | | 2016 |
| Atlas Worldwide L.P. | | 2009 |
| Atlase Ventures LP | | 2016 |
| Atlasecure Ltd | Information & communication | 2020 |
| Atmis LP | | 2014 |
| Atmos Consulting Limited | Professional & scientific | 2007 |
| Atmp Expert Ltd | Professional & scientific | 2023 |
| Atoll Investments Ltd | Real estate | 2022 |
| Atom (TPM) Limited | Professional & scientific | 2013 |
| Atom Concierge Limited | Real estate | 2024 |
| Atom Design Ltd. | Professional & scientific | 1999 |
| Atom Sales Limited | Administrative & support | 2024 |
| Atom Scotland Limited | Manufacturing | 2018 |
| Atomar LP | | 2016 |
| Atomic Mania LP | | 2017 |
| Atomic Punk Pictures Ltd | Information & communication | 2026 |
| Atomik International LP | | 2023 |
| Atomscale Ltd | Information & communication | 2019 |
| Aton Clinic Ltd | Health & social care | 2020 |
| Atoracing LP | | 2016 |
| Atos APF Scotland LP | | 2014 |
| Atos Asps Scotland LP | | 2014 |
| Atos CS Scotland LP | | 2013 |
| ATP Ventures Ltd. | Arts & recreation | 2004 |
| Atpc Consulting Ltd | Other services | 2019 |
| ATR Repairs Domestic & Commercial Ltd | Other services | 2021 |
| ATR Sawmill Limited | Manufacturing | 2016 |
| Atrex Trade LP | | 2016 |
| Atria Brokers LP | | 2014 |
| Atrium Student Accommodation Ltd | Hospitality | 2022 |
| Atrium Trading L.P. | | 2016 |
| Atropatena AZ LP | | 2015 |
| ATS Atlas Travel Solutions Scotland and Ireland Limited | Administrative & support | 2014 |
| Atsb Ltd | Wholesale & retail | 2019 |
| Atsix Limited | Professional & scientific | 2020 |
| ATT Research Consultancy Ltd | Professional & scientific | 2012 |
| Atta Restaurants Ltd | Hospitality | 2021 |
| Attacat Ltd. | Information & communication | 2000 |
| Attainmap Ltd | Information & communication | 2026 |
| Attentivics Ltd | Information & communication | 2016 |
| Attic in the Town Ltd | Hospitality | 2017 |
| Attic Rush Limited | Professional & scientific | 2019 |
| Attica Alliance LP | | 2016 |
| Attieroo Ltd | Real estate | 2026 |
| Attlinger LP | | 2015 |
| Atton Properties Limited | Construction | 2023 |
| Atuvi Limited | Wholesale & retail | 2025 |
| Atypical Solutions Ltd | Wholesale & retail | 2021 |
| AU AI Solutions Ltd | Information & communication | 2025 |
| AU Alchemist Limited | Wholesale & retail | 2014 |
| AU Gourmand Boulangerie Ltd | Manufacturing | 2018 |
| AU145 Limited | Construction | 2025 |
| Aubin Engineering | | 1994 |
| Aubrey Capital International Limited | Financial services | 2022 |
| Aubrey Capital Management EBT Limited | Professional & scientific | 2024 |
| Aubrey Capital Management Limited | Financial services | 2006 |
| Aubrey Strawberry Ltd | Hospitality | 2015 |
| Auburn Trading LP | | 2014 |
| Aubussondelpon Ltd | Financial services | 2024 |
| AUC9521 & Co Limited | Wholesale & retail | 2024 |
| Auchenblaik Ltd | Wholesale & retail | 2026 |