| Blue Shadows Films Ltd. | Information & communication | 2013 |
| Blue Sky Building Project Management Limited | Construction | 2012 |
| Blue Sky Interiors Limited | Construction | 2023 |
| Bluefern Developments Limited | Construction | 2024 |
| Bluegrove Financial Solutions Ltd. | Information & communication | 2007 |
| Bluegrove Wealth Limited | Financial services | 2015 |
| Blueprint Foundation | Other services | 2017 |
| Bluestone Lodge Holdings Ltd | Financial services | 2026 |
| BOB Weston Projects Limited | Professional & scientific | 2009 |
| Body by B Ltd | Arts & recreation | 2021 |
| Body by Hollie Ltd | Education | 2025 |
| Body Mechanix Osteo Limited | Other services | 2016 |
| Boeberry Limited | Real estate | 1973 |
| Bold by Design Limited | Professional & scientific | 2019 |
| Bolide Technology (UK) Limited | Professional & scientific | 2025 |
| Bondmason Client Ltd | Professional & scientific | 2015 |
| Boom Inc. Technologies UK Ltd | Information & communication | 2025 |
| Boom Vang Ltd | Professional & scientific | 2024 |
| Borodale Residents Association Limited | Administrative & support | 1984 |
| Bossyboss Limited | Professional & scientific | 2022 |
| Boston Medical Billing Limited | Real estate | 2014 |
| Both Worlds Clothing Limited | Wholesale & retail | 2025 |
| Bound Engineering Limited | Construction | 2025 |
| Bourne Retail Limited | Wholesale & retail | 2010 |
| Bowden Mayes Limited | Professional & scientific | 2009 |
| Bower Heath Partners Limited | Professional & scientific | 2012 |
| Bowers House Property Limited | Real estate | 2024 |
| Bowers Walk Management Company Limited | Real estate | 1992 |
| Bowers Way Surgery Ltd | Health & social care | 2018 |
| Bowline Tide Limited | Professional & scientific | 2021 |
| Boxer EOT Limited | Other services | 2026 |
| Boxer Systems Limited | Administrative & support | 1990 |
| BPH Wealth Management LLP | | 2007 |
| Brackenbury Futures Ltd | Professional & scientific | 2023 |
| Brad and Dills Ltd | Hospitality | 2020 |
| Bradells Co. 2 Ltd | Arts & recreation | 2025 |
| Bradley Tax and Consulting Ltd | Professional & scientific | 2019 |
| Bragg Life Sciences Ltd | Administrative & support | 2026 |
| Bramble Estates (Land) Limited | Real estate | 2018 |
| Bramble Estates Limited | Other services | 1994 |
| Bramble Estates Property Investments Limited | Construction | 2018 |
| Brand Consulting Ltd | Professional & scientific | 2025 |
| Branksome Dene Gardens Management Company Limited | Households | 2000 |
| Bratic Integrated Solutions Ltd | Information & communication | 2021 |
| Brave Minds Project Ltd | Professional & scientific | 2020 |
| Bravo Group Limited | Hospitality | 2000 |
| Braybourne END Management Company Limited | Households | 2020 |
| Brazmuz Ltd | Professional & scientific | 2017 |
| Brenna Supported Living Care Ltd | Health & social care | 2025 |
| Brew & CRU Ltd | Hospitality | 2018 |
| Breww Ltd | Information & communication | 2018 |
| BRG Construction Services Ltd | Construction | 2019 |
| Brian Shaw Consulting Limited | Professional & scientific | 2008 |
| Bright Mind Tutoring & Coaching Ltd | Education | 2026 |
| Brightad Limited | Administrative & support | 1981 |
| Brighter Later Ltd | Professional & scientific | 2023 |
| Brindloy Ltd | Wholesale & retail | 2021 |
| Briorestaurantbar Ltd | Hospitality | 2024 |
| British South America Trading Company Ltd | Professional & scientific | 2023 |
| Broad Street Communications Limited | Professional & scientific | 2006 |
| Broad Street Place Developments Limited | Construction | 1964 |
| Broadfields 12 Ltd | Professional & scientific | 2021 |
| Broadlake Close Management Company (6-29) Limited | Households | 1988 |
| Broadoak Advisory Ltd | Professional & scientific | 2022 |
| Broken Lens Productions Limited | Information & communication | 2014 |
| Brookhouse Associates Limited | Information & communication | 2022 |
| Brooklands Court RTM Co Ltd | Households | 2018 |
| Brookmead Kennels Limited | Other services | 2023 |
| Broomco (4296) Limited | Construction | 2017 |
| Broomcraig Limited | Information & communication | 2014 |
| Broster Buchanan EBT Limited | Administrative & support | 2024 |
| Broster Buchanan Ltd | Administrative & support | 2015 |
| Broster Buchanan NO. 1 Limited | Administrative & support | 2017 |
| BRS Advisory Ltd | Professional & scientific | 2025 |
| Bryant Court Limited | Households | 2004 |
| Brynmor Lettings Limited | Real estate | 2019 |
| Brynmor Limited | Wholesale & retail | 2010 |
| BSB Alliance Ltd | Real estate | 2025 |
| BSB Construction Limited | Construction | 2011 |
| BSB Group Holdings Ltd | Financial services | 2025 |
| BSD Property Group Limited | Real estate | 2022 |
| Bsheard Ltd | Professional & scientific | 2026 |
| Bsmn Padel Tours Ltd | Information & communication | 2016 |
| Bssb Limited | Financial services | 2019 |
| BTK Consulting Ltd | Hospitality | 2019 |
| BU Spice Limited | Hospitality | 2026 |
| Buchan Limited | Wholesale & retail | 2024 |
| Buddyboo & Bean Limited | Professional & scientific | 2011 |
| Buecker Interiors Ltd | Construction | 2025 |
| Building Compliance Certificate Ltd | Professional & scientific | 2024 |
| Building Dispute Advice Services Limited | Professional & scientific | 2005 |
| Built UP (UK) Limited | Professional & scientific | 2025 |
| Burdock Investments Limited | Financial services | 2013 |
| Burgess Architectural Products Limited | Manufacturing | 1973 |
| Burgess Metal Limited | Manufacturing | 2020 |
| Burke Geophysical Consultancy Ltd | Mining & quarrying | 2025 |
| Business Measures Limited | Information & communication | 2021 |
| BW Alliance Limited | Wholesale & retail | 2023 |
| Bwsco Ltd | Financial services | 2026 |
| BXC Building and Property Surveyors Ltd | Professional & scientific | 2025 |