| Blackstar Property Partners Ltd | Real estate | 2025 |
| Blackwater Baling Limited | Agriculture & fishing | 2012 |
| Blackwater Commodities Ltd | Information & communication | 2025 |
| Blackwater Country Events Limited | Other services | 2013 |
| Blackwater Developments Limited | Construction | 2024 |
| Blackwater Fabrications Ltd | Administrative & support | 2004 |
| Blackwater Partners Limited | Extraterritorial | 2013 |
| Blackwater Property Solutions & Investments Ltd | Real estate | 2020 |
| Blackwater Quay Limited | Hospitality | 2023 |
| Blackwater Surveyors Limited | Professional & scientific | 2025 |
| Blackwater Wealth Management Limited | Financial services | 2012 |
| Blades & Scissors Ltd | Other services | 2018 |
| Blakdog Ltd | Professional & scientific | 2022 |
| Blake Financial Planning Ltd | Financial services | 2016 |
| Blakes DRY Cleaners Limited | Other services | 2006 |
| Blakes FM Ltd | Administrative & support | 2025 |
| Blakes Resourcing Ltd | Administrative & support | 2026 |
| Blakeswood Consulting Limited | Professional & scientific | 2019 |
| Blancheco Limited | Other services | 2014 |
| Blancheco Properties Ltd | Real estate | 2018 |
| Blankson’S Linen Hire & Laundry Ltd | Transport & logistics | 2020 |
| Blasford Hill Fisheries Limited | Arts & recreation | 2015 |
| Blaze Equestrian Ltd | Wholesale & retail | 2021 |
| Blaze Food Ltd | Hospitality | 2026 |
| Blend Protein Ltd | Wholesale & retail | 2024 |
| Blended Creative Ltd | Administrative & support | 2024 |
| Blenheim Barnes Limited | Financial services | 2010 |
| Blenheim Consultancy Services Limited | Real estate | 2006 |
| Blenheim EOT Limited | Professional & scientific | 2024 |
| Blenstock Flat Management Company Limited | Households | 1983 |
| Blicken Synths Ltd | Wholesale & retail | 2018 |
| Bligh Maritime Consulting Ltd | Professional & scientific | 2019 |
| Bling Fashions Limited | Wholesale & retail | 2016 |
| Blinq Licensing Agency Limited | Wholesale & retail | 2026 |
| Bliss Accounting Services Limited | Professional & scientific | 2006 |
| Blisscare Services Limited | Health & social care | 2026 |
| Block Stone Ltd | Mining & quarrying | 1995 |
| Blockbeats Limited | Information & communication | 2020 |
| Blockchain Bogle Ltd | Information & communication | 2024 |
| Blockmaester Limited | Extraterritorial | 2024 |
| Bloom Bell Childcare Ltd | Other services | 2025 |
| Bloomback Limited | Administrative & support | 2024 |
| Bloomfield Construction Limited | Construction | 1983 |
| Bloomfield Contracts Limited | Administrative & support | 2010 |
| Bloomfold (Beaux Arts) Limited | Households | 2019 |
| Bloomfold Developments Limited | Extraterritorial | 2004 |
| Bloomfold Limited | Construction | 2000 |
| Bloomnode Limited | Information & communication | 2026 |
| Blooms Beauty Academy Limited | Education | 2020 |
| Blore Edwards Precision Ltd | Manufacturing | 2025 |
| Blpl Limited | Real estate | 2003 |
| Blue Badger Financial Limited | Financial services | 2017 |
| Blue Bay Care Services Ltd | Real estate | 2022 |
| Blue Chip Commercial Ltd | Real estate | 2025 |
| Blue COW Global Ltd | Professional & scientific | 2020 |
| Blue Coys Capital Limited | Financial services | 2022 |
| Blue Flag Tyres Ltd | Wholesale & retail | 2026 |
| Blue Lava Architecture Limited | Professional & scientific | 2017 |
| Blue Lava Limited | Professional & scientific | 2010 |
| Blue Light Integrity Ltd | Professional & scientific | 2024 |
| Blue Lion Baddow Limited | Hospitality | 2018 |
| Blue Moon Antiques & Interiors Ltd | Wholesale & retail | 2019 |
| Blue Ocean 138 Ltd | Hospitality | 2022 |
| Blue Ocean Imports Ltd | Wholesale & retail | 2019 |
| Blue Phoenix Redbourne Drive Ltd | Construction | 2026 |
| Blue Print Atelier Ltd | Wholesale & retail | 2014 |
| Blue Products Ltd | Wholesale & retail | 2026 |
| Blue Strawberry Restaurants (Holdings) Limited | Hospitality | 2015 |
| Blue Tang Productions Ltd | Information & communication | 2021 |
| Blue Tiger Marketing Ltd | Professional & scientific | 1999 |
| Blue Top Property Developments Ltd | Construction | 2023 |
| Blue TUB Installations Limited | Construction | 2018 |
| Blue Tulip Ltd | Professional & scientific | 2026 |
| Bluebell Homecare Limited | Health & social care | 2018 |
| Blueberry Studio Ltd | Information & communication | 2015 |
| Bluecrest Property Developments Limited | Construction | 2024 |
| Blueflame Resolutions Ltd | Construction | 2024 |
| Blueoak Fusion Ltd | Wholesale & retail | 2025 |
| Bluepod Media Worldwide Ltd | Professional & scientific | 2007 |
| Blueprint Engineering Limited | Manufacturing | 2006 |
| Blueprint Real Estate Ltd | Real estate | 2024 |
| Bluerock Investment Properties Limited | Real estate | 2018 |
| Blues at Barleylands CIC | Hospitality | 2025 |
| Bluesky Landscaping Ltd | Construction | 2024 |
| Bluesquare Homes (149 Kiln Road) Limited | Construction | 2021 |
| Bluesquare Homes (Billericay) Ltd | Construction | 2019 |
| Bluesquare Homes (Potash Road) Limited | Construction | 2019 |
| Bluesquare Homes (the Chase) Limited | Real estate | 2022 |
| Bluesquare Homes (Thundersley) Limited | Construction | 2019 |
| Bluesquare Homes Limited | Construction | 2017 |
| Bluetorque Services Ltd | Wholesale & retail | 2025 |
| Bluewave Infotech Limited | Information & communication | 2024 |
| Bluka Labs Ltd | Information & communication | 2025 |
| Blume Lifestyle Limited | Wholesale & retail | 2015 |
| Blumio Limited | Administrative & support | 2018 |
| Blush & Bitters Ltd | Hospitality | 2026 |
| Bm's Contracts Limited | Construction | 2026 |
| BMD Electrical Limited | Construction | 2014 |
| Bmjc Contracting Limited | Professional & scientific | 2025 |
| BMS Knightsbridge Limited | Other services | 2006 |