| Antica Transport Ltd | Transport & logistics | 2025 |
| Antonio Transport Ltd | Transport & logistics | 2021 |
| Antony Neal Ltd | Information & communication | 2013 |
| Antu Mobility Ltd | Wholesale & retail | 2025 |
| AP Boston Ltd | Wholesale & retail | 2020 |
| AP Energy Ltd | Energy | 2026 |
| Apex Plastics Ltd | Construction | 2025 |
| Apex Property Partners Limited | Real estate | 2026 |
| Apexmesh Ltd | Information & communication | 2026 |
| Apple & Tree Limited | Health & social care | 2022 |
| APS Boston Ltd | Other services | 2022 |
| Arbor Club Boston Limited | Hospitality | 2025 |
| Arco Travel LT Limited | Transport & logistics | 2017 |
| Aree Ltd | Wholesale & retail | 2013 |
| Arga Solutions Ltd | Transport & logistics | 2021 |
| Argyle Street Management Company Limited | Households | 2015 |
| ARK Biomass Limited | Extraterritorial | 2017 |
| ARK Fabricators Limited | Extraterritorial | 2011 |
| Arlette Properties Ltd | Real estate | 2024 |
| Armada Couture Ltd | Wholesale & retail | 2025 |
| Armaroof Ltd | Construction | 2026 |
| ARN Architectural Ltd | Professional & scientific | 2023 |
| Aron's Transport Ltd | Transport & logistics | 2018 |
| Aronia (UK) Ltd | Wholesale & retail | 2014 |
| Arslan Catering Limited | Hospitality | 2015 |
| Art Camp UK Ltd | Health & social care | 2019 |
| Art of Circus Limited | Arts & recreation | 2003 |
| Artisan Bakery 1 Ltd | Hospitality | 2025 |
| Arundell Hotel (Boston) Limited | Hospitality | 2014 |
| Arvid Ltd | Transport & logistics | 2015 |
| Arvyveza. Ltd | Transport & logistics | 2021 |
| ASC Rental Properties Ltd | Real estate | 2021 |
| Ashlie's Aesthetics Ltd | Health & social care | 2024 |
| Ashton Escapes Limited | Hospitality | 2019 |
| Asia Market Limited | Wholesale & retail | 2023 |
| ASL Group Holdings Ltd | Financial services | 2023 |
| Aslat Limited | Hospitality | 2024 |
| ASM UK Motors Limited | Wholesale & retail | 2016 |
| Asperton Management Company Limited | Real estate | 2012 |
| Aspire Counselling Services Ltd | Health & social care | 2017 |
| ASR Garden Services Ltd | Administrative & support | 2025 |
| Astalija Ltd | Transport & logistics | 2026 |
| Astar Badminton Ltd | Wholesale & retail | 2026 |
| AT Dent Limited | Health & social care | 2009 |
| Atalaya Lincs Limited | Real estate | 2015 |
| ATC Installations Limited | Construction | 2007 |
| ATD Agricultural Ltd | Agriculture & fishing | 2023 |
| Atlas Inflatable Services Ltd | Professional & scientific | 2017 |
| ATM Driver Ltd | Transport & logistics | 2022 |
| Attenova Ltd | Health & social care | 2026 |
| Audrugita Ltd | Transport & logistics | 2022 |
| Augmented Tech Services Ltd | Information & communication | 2019 |
| Aureum Aesthetics Ltd | Arts & recreation | 2025 |
| Aurora Adventure Associates Limited | Construction | 2013 |
| Auto CIP Services Ltd | Wholesale & retail | 2024 |
| Auto Port Car Services Ltd | Wholesale & retail | 2022 |
| Auto Repairs and Rent a Ramp Ltd | Wholesale & retail | 2022 |
| Auto Spa Club Limited | Administrative & support | 2025 |
| Auto VMV Ltd | Transport & logistics | 2019 |
| Auto-Tec Boston Ltd | Wholesale & retail | 2024 |
| Autokesta Ltd | Transport & logistics | 2019 |
| Automarket Pro Limited | Wholesale & retail | 2026 |
| Autotruck Ltd | Wholesale & retail | 2020 |
| AV Permanent Make UP Academy Ltd | Real estate | 2025 |
| Avax Holdings Limited | Real estate | 2021 |
| Avenzoar Ltd | Health & social care | 2014 |
| Aviway Limited | Professional & scientific | 2002 |
| Avlon Investments Limited | Real estate | 2023 |
| Avlon Leisure Limited | Financial services | 2023 |
| Avoda Housing CIC | Hospitality | 2026 |
| AWS MOT and Repair Centre (Boston) Ltd | Wholesale & retail | 2025 |
| Ayan Trans Ltd | Transport & logistics | 2016 |
| AZ Building Limited | Real estate | 2021 |
| Aztec Drives Limited | Construction | 2005 |
| Aztech Designs Limited | Professional & scientific | 2007 |
| Azymuth Ltd | Wholesale & retail | 2019 |
| B & a Services Ltd | Wholesale & retail | 2025 |
| B & F Electrical Ltd | Manufacturing | 2018 |
| B & L Engineering Ltd | Manufacturing | 2016 |
| B & L Rylott Limited | Extraterritorial | 2008 |
| B & ST Transport Limited | Transport & logistics | 2003 |
| B Bush & Sons Limited | Agriculture & fishing | 2010 |
| B Cole SON & Daughters Ltd | Transport & logistics | 2022 |
| B S Medical Limited | Health & social care | 2003 |
| B&L Autorepair Ltd | Wholesale & retail | 2023 |
| B&W Infra Services Ltd | Professional & scientific | 2026 |
| B.I.G Recovery & Transport Ltd | Transport & logistics | 2026 |
| Babi T&C Limited | Construction | 2019 |
| Babs Medical Limited | Health & social care | 2024 |
| Baby MOO Limited | Wholesale & retail | 2018 |
| Bain & Company United Kingdom LLP | | 2023 |
| Ballantyne Robinson Ltd | Financial services | 2025 |
| Baltic Food & Grocery Ltd | Wholesale & retail | 2005 |
| Baltic Food Park, Boston Ltd | Wholesale & retail | 2014 |
| Baltic Road Limited | Transport & logistics | 2019 |
| Baltic Shop Limited | Wholesale & retail | 2010 |
| Bandeja Clothing Limited | Wholesale & retail | 2026 |
| Baolu Global Consulting Limited | Professional & scientific | 2025 |
| Bar and Away Ltd | Hospitality | 2022 |
| Bar-Ren Ltd | Transport & logistics | 2022 |