| Block Made Entertainment Ltd | Wholesale & retail | 2025 |
| Blockstreet Ltd | Wholesale & retail | 2025 |
| Bloomsbury Wealth Limited | Real estate | 2024 |
| Blorenge Holdings Ltd | Financial services | 2025 |
| Blossom Bay Care Ltd | Health & social care | 2025 |
| Blossom Grove Management Limited | Real estate | 2010 |
| Blowria Ltd | Wholesale & retail | 2025 |
| BLR29 Consulting Limited | Information & communication | 2020 |
| Blrd Consulting Ltd | Information & communication | 2026 |
| Blrh Group Ltd | Financial services | 2025 |
| Blrh Payroll Ltd | Hospitality | 2025 |
| BLS & ASH Ltd | Real estate | 2026 |
| BLU Earth Consulting Ltd | Professional & scientific | 2014 |
| Blue Abacus Homes Ltd | Extraterritorial | 2022 |
| Blue Arch Property Solutions Limited | Real estate | 2026 |
| Blue Crystal Computing Ltd | Information & communication | 1995 |
| Blue Earth Biochar Limited | Professional & scientific | 2023 |
| Blue Heart Care Group Ltd | Administrative & support | 2019 |
| Blue Hibiscus Hair Artistry Ltd | Wholesale & retail | 2025 |
| Blue House Farm Barns Management Company Limited | Households | 1989 |
| Blue Ocean Marine Foods Ltd | Wholesale & retail | 2024 |
| Blue Oyster Fish Bar Ltd | Hospitality | 2020 |
| Blue Phoenix Software Limited | Information & communication | 2014 |
| Blue Sea Art Ltd | Education | 2022 |
| Blue Skies Investments Limited | Real estate | 2026 |
| Blue Skies Living Limited | Real estate | 2025 |
| Blue Steel Products Ltd | Wholesale & retail | 2025 |
| Blue Vision Enterprise Limited | Arts & recreation | 2013 |
| Blue Vision Properties Ltd | Real estate | 2019 |
| Blue Wire Solutions Limited | Information & communication | 2025 |
| Bluebee-Engineering Ltd | Real estate | 2024 |
| Bluebell First AID (Bristol) Ltd | Health & social care | 2024 |
| Bluebell Wellness Limited | Health & social care | 2019 |
| Blueberry Data Limited | Information & communication | 2025 |
| Bluebird Photography Ltd | Arts & recreation | 2023 |
| Bluecap Critical Minerals Limited | Professional & scientific | 2023 |
| Bluecap Resources Limited | Professional & scientific | 2020 |
| Bluecap Zinc (UK) Limited | Professional & scientific | 2026 |
| Bluecap Zinc Limited | Professional & scientific | 2026 |
| Bluecat Data Limited | Information & communication | 2025 |
| Bluefin Living Ltd | Manufacturing | 2015 |
| Blueprint(Newport) Ltd | Administrative & support | 2025 |
| Bluesgreen Ltd | Wholesale & retail | 2024 |
| Blueshore Real Estate Ltd | Real estate | 2020 |
| Bluesky Investment Group Limited | Real estate | 2021 |
| Bluesky Unified Communications Limited | Information & communication | 2021 |
| Bluestone Brewing Company Limited | Manufacturing | 2013 |
| Bluestone Building and Shopfitting Limited | Construction | 2018 |
| Bluestone Wealth Management Limited | Financial services | 2008 |
| Bluetube Group Ltd | Financial services | 2024 |
| Bluetube Scaffolding Ltd | Construction | 2023 |
| Blueygreen Limited | Information & communication | 2002 |
| Blush Tanning & Beauty Salon Ltd | Other services | 2010 |
| BM Auto Repairs Limited | Administrative & support | 2017 |
| Bmathew Ltd | Health & social care | 2025 |
| BMG Arch Ltd | Financial services | 2025 |
| BMG Design Limited | Professional & scientific | 2008 |
| BMS Automation Limited | Professional & scientific | 2022 |
| BMS Trading Ltd | Wholesale & retail | 2018 |
| Bnb-Biofuels Limited | Administrative & support | 2017 |
| Bnke Ltd | Administrative & support | 2016 |
| BOB Bentley Design Ltd | Information & communication | 2004 |
| BOB Cave Supplies and Services Limited | Manufacturing | 1999 |
| Bobby's Bistro Ltd | Hospitality | 2023 |
| Bobbys Fruit MIX Ltd | Wholesale & retail | 2026 |
| Bobbys Property Maintenance Ltd | Construction | 2024 |
| Bobby’S Bakes Ltd | Hospitality | 2026 |
| Bobl Bach Clare Trinant Ltd | Health & social care | 2025 |
| BOD Consulting Ltd | Professional & scientific | 2022 |
| Bodega (Lakeside) Ltd | Wholesale & retail | 2023 |
| Bods Construction Ltd | Construction | 2020 |
| Boetts Ltd | Households | 2026 |
| Bogaz Catering Ltd | Hospitality | 2024 |
| Bohemia Farm Limited | Administrative & support | 2015 |
| Boiler Plant Maintenance (Cardiff) Limited | Construction | 2000 |
| Bold Moves Property Ltd | Real estate | 2025 |
| Bolewa Limited | Wholesale & retail | 2025 |
| Bolly BOP Ltd | Hospitality | 2020 |
| Boltbackautomobile Limited | Wholesale & retail | 2025 |
| Bombrugby Ltd | Wholesale & retail | 2026 |
| Bonanni Ltd | Hospitality | 2023 |
| Bonavolentia Limited | Information & communication | 2014 |
| Bond Lane Research Limited | Professional & scientific | 2009 |
| Boniface Management Limited | Professional & scientific | 2014 |
| Bonita Health Ltd | Health & social care | 2022 |
| Bonjorno Ltd | Hospitality | 2024 |
| Boost Beauty Limited | Education | 2022 |
| Boost Wealth Limited | Financial services | 2024 |
| Booth Analytics Ltd | Information & communication | 2026 |
| Booth Property Group Ltd | Real estate | 2018 |
| Borefence Ltd | Construction | 2009 |
| Borg Waste Management Limited | Water & waste | 2025 |
| Borley Developments Ltd | Construction | 2016 |
| Borley Laminates Ltd | Administrative & support | 2010 |
| Born Communication Limited | Professional & scientific | 2008 |
| Born Inventive Ltd | Wholesale & retail | 2020 |
| Boru Life Ltd | Wholesale & retail | 2019 |
| Boss Storage Ltd | Transport & logistics | 2022 |
| Bossa Brothers Limited | Wholesale & retail | 2025 |
| Bossmanssweets Limited | Wholesale & retail | 2020 |