| B R Mellor Roofing & Property Maintenance Ltd | Construction | 2025 |
| B Salt Holdings Limited | Households | 2025 |
| B Smart Properties Ltd | Construction | 2015 |
| B Twenty Two Ltd | Financial services | 2024 |
| B W Capital Limited | Professional & scientific | 2010 |
| B W Dawes Plumbing & Maintenance Limited | Construction | 2021 |
| B&A Care Ltd | Administrative & support | 2019 |
| B&C Taxi Limited | Transport & logistics | 2025 |
| B&D Consulting Limited | Information & communication | 2011 |
| B&H Holdings Limited | Professional & scientific | 2016 |
| B&K Shakers Ltd | Hospitality | 2025 |
| B&M Building and Maintenance Ltd | Construction | 2017 |
| B&M Painting and Decorating Ltd | Construction | 2019 |
| B&N UK Property Management Ltd | Real estate | 2021 |
| B-Pak Limited | Real estate | 2019 |
| B. a. a. Group Ltd | Transport & logistics | 2024 |
| B.B.Y. Limited | Professional & scientific | 1995 |
| B.P. Plumbing, Heating and GAS Ltd | Construction | 2025 |
| B1 Direct Ltd | Professional & scientific | 2013 |
| B3B Enterprises Limited | Real estate | 2012 |
| B84 Global Trading Desk Limited | Information & communication | 2025 |
| B84 Systems Limited | Information & communication | 2026 |
| BA Specialised Systems Ltd | Professional & scientific | 2016 |
| Baan Design Studio Ltd | Professional & scientific | 2023 |
| Baan Thai Massages Limited | Other services | 2021 |
| Baba Sharwarma Limited | Hospitality | 2024 |
| Babkky Limited | Health & social care | 2025 |
| Baby Moo's Inc Ltd | Wholesale & retail | 2021 |
| BAC Building Services Ltd | Construction | 2023 |
| Baccello Cicchetti Limited | Hospitality | 2026 |
| Baccello Wine Limited | Hospitality | 2026 |
| Back & Neck Care Centre Limited | Health & social care | 2016 |
| Back on Track Mentoring Limited | Education | 2024 |
| Backruns Limited | Information & communication | 2024 |
| Backwell Solutions Limited | Professional & scientific | 2023 |
| Backyard Barbers (Dorset) Limited | Other services | 2024 |
| Bacon & Birdies Limited | Information & communication | 2025 |
| BAD Hand Coffee Limited | Hospitality | 2018 |
| Badassretro Ltd | Wholesale & retail | 2025 |
| Baddow Estates Limited | Construction | 2019 |
| Badger Heating Limited | Construction | 2008 |
| Badger Philatelics Limited | Wholesale & retail | 2010 |
| Baildon Lodge Freehold Limited | Real estate | 2023 |
| Bailey Hall Freehold Limited | Households | 2008 |
| Bakeer Ltd | Health & social care | 2019 |
| Bakeer Properties Ltd | Real estate | 2022 |
| Baker Love Jones Ltd | Financial services | 2026 |
| Baker Property Consultants Limited | Real estate | 2011 |
| Bakery Mews (Development) Limited | Households | 2016 |
| Baks Menswear Ltd | Wholesale & retail | 2019 |
| Balade Limited | Administrative & support | 2019 |
| Balanced Books Bookkeeping Ltd | Professional & scientific | 2026 |
| Balatoni Management Company Limited | Households | 1988 |
| Balcombe Court Residents Limited | Households | 2004 |
| Balcombe Tower Management Company Limited | Households | 1988 |
| Bald Drylining Ltd | Construction | 2026 |
| Bali Tanning Rooms Ltd | Other services | 2019 |
| Balloonific Ltd | Wholesale & retail | 2020 |
| Ballroom Reloved Limited | Wholesale & retail | 2023 |
| Balmoral Court (Bournemouth) Limited | Real estate | 2004 |
| Balmoral Court (Highcliffe) RTM Company Limited | Households | 2019 |
| Balmoral Court Parkstone Limited | Households | 1987 |
| Baltic Heritage CIC | Administrative & support | 2025 |
| Bambara Limited | Extraterritorial | 2012 |
| Bambrey Bodyshop Ltd | Wholesale & retail | 2011 |
| Bambuu Asia Ltd | Hospitality | 2026 |
| Bamm Lettings Ltd | Real estate | 2025 |
| Banana & Fish Estates Limited | Real estate | 2021 |
| Bang Tidy Cleaning South Ltd | Other services | 2013 |
| Bani Property Limited | Real estate | 2024 |
| Banks Capital Limited | Financial services | 2020 |
| Bankside Press Ltd | Information & communication | 2016 |
| Banq Bars Limited | Hospitality | 2025 |
| Banridge Limited | Households | 1985 |
| Bar Republiq Limited | Hospitality | 2021 |
| Bar South Ltd | Hospitality | 2024 |
| Baraka Property Ltd | Real estate | 2020 |
| Barb's Free From Cakes Limited | Manufacturing | 2025 |
| Barbara Walden Glass Engraving Limited | Arts & recreation | 2014 |
| Barbs Galore Ltd | Professional & scientific | 2018 |
| Barclay Court RTM Company Limited | Households | 2009 |
| Bare Perfection Limited | Other services | 2024 |
| Barents Project Management LLP | | 2016 |
| Bargates Houses Management Limited | Households | 2016 |
| Bargates Property Ltd | Real estate | 2022 |
| Barham Close Management Limited | Households | 2007 |
| Barker and Barker Pets Limited | Wholesale & retail | 2011 |
| Barking Road Properties Limited | Real estate | 1964 |
| Barkinmad Property Ltd | Real estate | 2022 |
| Barnacle's Fish and Chips Ltd | Hospitality | 2025 |
| Barnes Aerial Company Limited | Construction | 2009 |
| Barnes Andrew Accountancy Limited | Professional & scientific | 2019 |
| Barnes Ingram and Associates LLP | | 2013 |
| Barnes Ingram Limited | Financial services | 2012 |
| Barney Couch Technical Services Limited | Professional & scientific | 2023 |
| Barnwell Gate Limited | Construction | 2020 |
| Barolo Limited | Real estate | 2002 |
| Barolo Properties Limited | Construction | 2025 |
| Baron Construction (UK) Limited | Real estate | 1993 |
| Barons Court Freehold Limited | Households | 2017 |