| Brentwood Recycling Services Limited | Water & waste | 2013 |
| Brera Public Relations Limited | Professional & scientific | 2013 |
| Brewblack Ltd | Wholesale & retail | 2020 |
| Brian Casal Limited | Construction | 2016 |
| Brickrock Limited | Construction | 2025 |
| Brigfort Limited | Wholesale & retail | 2024 |
| Bright Beginnings Pre-School Limited | Education | 2010 |
| Bright Boots Coaching Ltd | Education | 2021 |
| Bright Horizon Pantry Supplies Ltd | Wholesale & retail | 2023 |
| Bright Motion Limited | Information & communication | 2016 |
| Bright Stark Electrical Ltd. | Administrative & support | 2018 |
| Bright UK LED Co Limited | Wholesale & retail | 2015 |
| Brilliant Brains Ltd | Wholesale & retail | 2020 |
| Brindle Installations Limited | Administrative & support | 2000 |
| Bring the House Events Limited | Other services | 2020 |
| Briody Plumbing & Heating Limited | Construction | 2026 |
| Brisel Consult Ltd | Professional & scientific | 2013 |
| Brisket (U.K) Limited | Hospitality | 2022 |
| Brit Fried Chicken Limited | Hospitality | 2017 |
| Britannia Adhesives Limited | Manufacturing | 1986 |
| Britannia Kitchen Ltd | Hospitality | 2024 |
| Britannia Property Management & Lettings Ltd | Real estate | 2018 |
| Britannia Study Centres Limited | Education | 2011 |
| Britdure Bazaar Limited | Wholesale & retail | 2025 |
| British Ltd | Information & communication | 2026 |
| Britlink Cargo Ltd | Transport & logistics | 2013 |
| Britnell Group Ltd | Financial services | 2024 |
| Britnova Solutions Ltd | Wholesale & retail | 2024 |
| Britso Ltd | Wholesale & retail | 2020 |
| Broad Fortified Services Ltd | Wholesale & retail | 2024 |
| Broadfield Design & Build Ltd | Construction | 2023 |
| Broadfield Group Holdings Limited | Other services | 2023 |
| Broadfield Homes (Pippins Place) Limited | Construction | 2025 |
| Broadfield Homes Limited | Construction | 2018 |
| Broadfield Probate Partners Limited | Real estate | 2025 |
| Broadfield Real Estate Limited | Real estate | 2022 |
| Broadfield Rochester Development Limited | Construction | 2022 |
| Broadgate Ltd | Real estate | 2018 |
| Broadleaf Tree Surgery Limited | Agriculture & fishing | 2017 |
| Broadway Properties (Southend) Limited | Extraterritorial | 2021 |
| Brocagh Homes Ltd | Real estate | 2020 |
| Brocks Development Limited | Construction | 1999 |
| Brockwell Fencing Limited | Construction | 2019 |
| Brogan and Bailey Limited | Other services | 2025 |
| Broker Solutions Limited | Administrative & support | 2022 |
| Brokers Incorporated Limited | Financial services | 2012 |
| Broma Art Enamellers Limited | Manufacturing | 1958 |
| Bronel Group Holdings Limited | Financial services | 2016 |
| Bronel Group Limited | Transport & logistics | 1989 |
| Brook Mountain Developments Limited | Construction | 2023 |
| Brook Street Body and Paint Limited | Wholesale & retail | 2017 |
| Brooklands Medical Services Ltd | Health & social care | 2024 |
| Brooks Waste Limited | Water & waste | 2008 |
| Brothers Halal Butchers Limited | Wholesale & retail | 2020 |
| Brothers Halal Limited | Wholesale & retail | 2026 |
| Brothers in Arts Tattoo Company Limited | Other services | 2018 |
| Brown & Carroll (London) Limited | Manufacturing | 1994 |
| Brown & Co LLP | | 2006 |
| Brown & Cooke Construction Limited | Construction | 2020 |
| Brown FOX Ltd | Wholesale & retail | 2010 |
| Brown's Car Company Ltd | Wholesale & retail | 2019 |
| Browns Groundworks and Construction Limited | Construction | 2022 |
| Browns Taxation & Accountancy Group Ltd | Professional & scientific | 2025 |
| Browns Taxation & Accountancy LLP | | 2024 |
| Brows & Blends by Nikki Ltd | Other services | 2022 |
| Browz Beauty Ltd | Other services | 2015 |
| BRUCE3 Ltd | Wholesale & retail | 2021 |
| Bruno Fitness Limited | Arts & recreation | 2017 |
| Bruzas Ltd | Construction | 2025 |
| Bryants Carpentry & Construction Ltd | Construction | 2016 |
| Bryn Property Developments Ltd | Real estate | 2026 |
| Brynleigh Technology Limited | Manufacturing | 1992 |
| BS Cars Ltd | Wholesale & retail | 2015 |
| BS Contractors Ltd | Construction | 2014 |
| BS Service Company Ltd | Transport & logistics | 2024 |
| Bsbea Limited | Health & social care | 2023 |
| BSI Trinal Limited | Wholesale & retail | 2024 |
| BSK London Limited | Hospitality | 2014 |
| BSO Global Ltd | Wholesale & retail | 2026 |
| Btcm Limited | Construction | 1986 |
| BTK Bathrooms Limited | Construction | 2015 |
| BTL Essex Ltd | Real estate | 2024 |
| BTL NO.1 Ltd | Administrative & support | 2017 |
| BTM Electrical Limited | Construction | 2022 |
| BTM Properties Ltd | Real estate | 2019 |
| Btmk Financial Services Limited | Financial services | 2024 |
| Btmk LLP | | 2005 |
| Btmk Solicitors Limited | Professional & scientific | 2005 |
| BTP Automotives Ltd | Wholesale & retail | 2025 |
| BTR CA Limited | Extraterritorial | 2019 |
| BTS Communications Ltd | Construction | 2024 |
| Bubble Bliss Baby Spa Ltd | Other services | 2025 |
| Bubble Mania Winter Wonderland Ltd | Hospitality | 2025 |
| Bubble Trade Ltd | Wholesale & retail | 2020 |
| Bubby and Squirrel Ltd | Wholesale & retail | 2023 |
| Buck Design Limited | Information & communication | 2009 |
| Bucks Property Agents Limited | Real estate | 2003 |
| Bucksbury & Co Ltd | Agriculture & fishing | 2018 |
| BUD Funding Limited | Financial services | 2020 |
| Bugg Estates Ltd | Real estate | 2022 |