| Ashley Chicken Limited | Hospitality | 2018 |
| Ashley Court Parkstone Limited | Households | 1989 |
| Ashtree Meadows Management Company Limited | Extraterritorial | 2003 |
| Asian Food Outlet Ltd | Hospitality | 2018 |
| ASK It's Done Limited | Information & communication | 2002 |
| ASL Technology Limited | Professional & scientific | 2025 |
| Aspire Architects (Christchurch) Limited | Professional & scientific | 2025 |
| Aspire Bathrooms & Kitchens Ltd | Construction | 2010 |
| Aspire UAV Ltd | Professional & scientific | 2025 |
| Asset & Capital Investments Limited | Administrative & support | 2014 |
| AST Plumbing Ltd | Construction | 2015 |
| Atch Ltd | Information & communication | 2022 |
| ATL Europe (POA) Limited | Extraterritorial | 2019 |
| ATL Europe (UK) Limited | Professional & scientific | 2019 |
| Atlantic Marine Interiors Limited | Manufacturing | 2010 |
| Atlas Contract Furniture Holdings Ltd | Financial services | 2018 |
| Atlas Contract Furniture Limited | Manufacturing | 2009 |
| Atlas Investments Ltd | Real estate | 2018 |
| Atlas Window Cleaning Ltd | Administrative & support | 2024 |
| Atorro Sports Ltd | Hospitality | 2019 |
| Audio Visual Installation Limited | Professional & scientific | 2008 |
| Aurea Tessera Holdings (Dorset) Ltd | Financial services | 2025 |
| Austin Group Ltd | Real estate | 2023 |
| Autism Unlimited Limited | Education | 1990 |
| Avalon 2015 Limited | Households | 2015 |
| Avavo Ltd | Wholesale & retail | 2015 |
| Avenue Court (Christchurch) Management Limited | Households | 2004 |
| Aviary Hospitality Limited | Hospitality | 2019 |
| Aviation Medicals in Wessex Services Limited | Health & social care | 2018 |
| Avic Cabin Systems (UK) Limited | Manufacturing | 2018 |
| Avionics Solutions Limited | Manufacturing | 2013 |
| Avon Electrical South Ltd | Construction | 2023 |
| Avon Engineering Limited | Administrative & support | 2024 |
| Avon Glade Management Company Limited | Households | 1988 |
| Avon LEE Lodge Limited | Health & social care | 2012 |
| Avon Renewables Ltd | Construction | 2020 |
| Avon Stores Limited | Wholesale & retail | 2003 |
| Avon Trading Co Ltd | Wholesale & retail | 2012 |
| Avon Tyrrell Estate Nominees (NO.1) Limited | Administrative & support | 2007 |
| Avon Tyrrell Estate Properties Limited | Real estate | 2015 |
| Avon Tyrrell Farms Limited | Agriculture & fishing | 1974 |
| Avon Wharf Management Company Limited | Households | 1979 |
| AVS Bransgore Limited | Wholesale & retail | 2024 |
| AW Partnership Ltd | Other services | 2016 |
| AW Partnership Property Limited | Real estate | 2022 |
| AXE Head Contracting Ltd | Financial services | 2016 |
| Axis Marine Solutions Ltd | Manufacturing | 2024 |
| AXLR8.COM Limited | Information & communication | 1993 |
| Aztek Developments (Alma) Ltd | Construction | 2025 |
| B & R Electrical Contractors Limited | Construction | 2008 |
| B D Catering Limited | Hospitality | 2009 |
| B J Parrett & SON Limited | Construction | 2010 |
| B&W Plumbing and Heating Ltd | Construction | 2024 |
| B.W. Ring Limited | Administrative & support | 1972 |
| B2B Creative Studio Limited | Arts & recreation | 2007 |
| Backstage Music Limited | Arts & recreation | 2025 |
| BAD Karma Consulting Limited | Information & communication | 2021 |
| BAD Karma Investments Limited | Real estate | 2024 |
| Bailey Bridge Marina Ltd | Manufacturing | 2021 |
| Bait JAM Ltd | Agriculture & fishing | 2022 |
| Baldwin Advisory Services Ltd | Professional & scientific | 2010 |
| Ball Design Ltd | Administrative & support | 2025 |
| Ballard Homes South Ltd | Real estate | 2025 |
| Balmeton Ltd | Real estate | 2024 |
| Bamboo Cocktail Bar and Restaurant Ltd | Hospitality | 2025 |
| Banana Media Ltd. | Arts & recreation | 1998 |
| Barakath Foods Limited | Hospitality | 2026 |
| Bare Necessities Refill Co Limited | Wholesale & retail | 2021 |
| Bare Skin Studio Ltd | Other services | 2024 |
| Barker & Wolf Ltd | Public administration | 2025 |
| Barlow Heating Limited | Construction | 2020 |
| Barnfield (Residents) Management Company Limited | Households | 1978 |
| Barnstomper Events Ltd | Hospitality | 2023 |
| Barons Court Flats Southbourne Limited | Households | 2003 |
| Barrack Road Tyres BH23 Ltd | Wholesale & retail | 2026 |
| Barrell Consultancy Limited | Information & communication | 2017 |
| Bartonnews Ltd | Wholesale & retail | 2022 |
| Basalt Global Limited | Energy | 2011 |
| Basalt Power Limited | Energy | 2019 |
| Bashley Park Limited | Hospitality | 1950 |
| Basingthwaighte PCS Ltd | Wholesale & retail | 2026 |
| Batten's Plumbing & Heating Ltd | Construction | 2024 |
| Bayside Ltd | Hospitality | 2022 |
| Baywood Homes Ltd | Real estate | 2024 |
| BC Autos (Christchurch) Ltd | Wholesale & retail | 2019 |
| BC Bookkeeping Limited | Professional & scientific | 2011 |
| BCP Competitions Ltd | Arts & recreation | 2025 |
| BCP Connect Limited | Other services | 2020 |
| BCP Exterior Cleaning Limited | Administrative & support | 2026 |
| Bcpr Technologies Ltd | Information & communication | 2023 |
| BD Spence Consulting Limited | Manufacturing | 2018 |
| Beachcomber Cafe (Barton on Sea) Limited | Hospitality | 2009 |
| Beachtide Limited | Hospitality | 1976 |
| Beagle Aerospace Limited | Manufacturing | 2011 |
| Beagle Aircraft Ltd | Manufacturing | 2020 |
| Beagle Composites Limited | Manufacturing | 2011 |
| Beagle MRO Limited | Manufacturing | 2011 |
| Beagle Precision Limited | Manufacturing | 2011 |
| Beagle Treatments Limited | Manufacturing | 2011 |
| Bearbelle Limited | Construction | 2010 |