| BIZ Grow Ltd | Wholesale & retail | 2022 |
| Biztravels Ltd | Administrative & support | 2026 |
| BK Law LLP | | 2008 |
| BL Construction and Property Services Limited | Real estate | 2019 |
| BL Management Services Ltd | Administrative & support | 2025 |
| BLA Distribution Ltd | Wholesale & retail | 2025 |
| Black Bear Construction Ltd | Construction | 2023 |
| Black Eagle Transfers Ltd | Transport & logistics | 2025 |
| Black Manor Group Ltd | Professional & scientific | 2022 |
| Black Mountain Holdings Limited | Real estate | 2016 |
| Blackburn and Tandoc Ltd | Professional & scientific | 2024 |
| Blackpearl Corporation Ltd | Transport & logistics | 2024 |
| Blackstone Detailing Ltd | Other services | 2024 |
| Blancote Limited | Financial services | 2022 |
| BLC Technology Limited | Information & communication | 2000 |
| Blerriot Ltd | Wholesale & retail | 2021 |
| Blogrex Enterprises Limited | Information & communication | 2025 |
| Bloomy Ltd | Wholesale & retail | 2025 |
| Blossom Fruits UK Ltd | Wholesale & retail | 2024 |
| Blossom Services International Ltd | Transport & logistics | 2025 |
| Blu-Gates Limited | Other services | 2011 |
| Blue FIR Estates Limited | Real estate | 2019 |
| Blue Pillar Solutions Ltd | Hospitality | 2025 |
| Blue Sky Horizon Property Ltd | Real estate | 2026 |
| Blueline Construction Limited | Construction | 2013 |
| Blueprint Carpentry and Construction Ltd | Construction | 2018 |
| Blueprint Safe Rooms Ltd | Construction | 2026 |
| Bluevalley Properties Ltd | Real estate | 2024 |
| BMJ Home Furnishing Ltd | Manufacturing | 2025 |
| BMX Limited | Wholesale & retail | 2017 |
| BNE London Properties Limited | Real estate | 2021 |
| Bnegestat Car Hire Ltd | Administrative & support | 2025 |
| Bog'Art Abseiling Ltd | Construction | 2025 |
| Bolt Automobiles Ltd | Wholesale & retail | 2026 |
| Boltx Logistics Limited | Transport & logistics | 2024 |
| Bonico Insights Ltd | Information & communication | 2020 |
| Boom London Events Ltd | Arts & recreation | 2025 |
| Bora Bora Properties Ltd | Real estate | 2023 |
| Borderless Incorporations Ltd | Wholesale & retail | 2025 |
| BOTLER360 Ltd | Information & communication | 2017 |
| Bouquets by Post Ltd | Wholesale & retail | 2024 |
| Bower & James Estates Ltd | Real estate | 2022 |
| Boyer Leisure Limited | Arts & recreation | 1988 |
| Brand Lawyers Limited | Professional & scientific | 2014 |
| Brands Urban Ltd | Wholesale & retail | 2026 |
| Brandsexpert Limited | Wholesale & retail | 2025 |
| Brandz Automotive Ltd | Wholesale & retail | 2018 |
| Brandz Property Group Ltd | Households | 2025 |
| Bravebird.Tech Ltd. | Information & communication | 2018 |
| Breakdown UNO Ltd | Wholesale & retail | 2024 |
| Breakthrough Medical Solutions Ltd | Information & communication | 2026 |
| Brenlyn Healthcare Ltd | Health & social care | 2021 |
| Brentford Motors Ltd | Wholesale & retail | 2022 |
| Brickbyte Commerce Ltd | Wholesale & retail | 2024 |
| Brickwork AB Limited | Construction | 2017 |
| Bright Chauffeurs Ltd | Transport & logistics | 2023 |
| Bright Glazing Ltd | Manufacturing | 2025 |
| Brightaura Cleaners Limited | Administrative & support | 2025 |
| Brightside Care Services Ltd | Health & social care | 2022 |
| Brikz Ltd | Real estate | 2025 |
| Brimmin Rigging Ltd | Arts & recreation | 2015 |
| Brindley Capital Ltd | Financial services | 2018 |
| Brit Drives Ltd | Administrative & support | 2023 |
| Britannia Auto Parts Ltd | Wholesale & retail | 2025 |
| Brite Management Ltd | Professional & scientific | 2024 |
| Britedge Academy Ltd | Professional & scientific | 2025 |
| Britmark Limited | Wholesale & retail | 2022 |
| Broadgate Power Limited | Administrative & support | 2026 |
| Brooklyn House (Freehold) Limited | Households | 2020 |
| Bros & Bolts Motors Ltd | Wholesale & retail | 2026 |
| Brow Extensions London Limited | Education | 2024 |
| Brum Motors Limited | Wholesale & retail | 2025 |
| BS and Sons London Limited | Wholesale & retail | 2017 |
| BS Wholesale Ltd | Wholesale & retail | 2025 |
| BSD Investment Holdings Ltd | Real estate | 2021 |
| BSS Builders Ltd | Construction | 2026 |
| BSS Security Ltd | Administrative & support | 2020 |
| BTN Media & Training Ltd | Education | 2020 |
| Btoi Ltd | Construction | 2025 |
| Btvk Consultancy Limited | Public administration | 2020 |
| Buckland Wear Ltd | Wholesale & retail | 2026 |
| Buffalo Gardening Limited | Other services | 2025 |
| Build Strong Building Ltd | Construction | 2026 |
| Building Project Specialists Ltd | Construction | 2026 |
| Building Site Ltd | Wholesale & retail | 2018 |
| Buildingsiteuk Ltd | Wholesale & retail | 2020 |
| Buildingster Limited | Construction | 2021 |
| Bulgar Build Ltd | Construction | 2015 |
| Buncup Ltd. | Administrative & support | 2000 |
| Bunn's Catering Limited | Hospitality | 2026 |
| Bunny Hmua Ltd | Other services | 2023 |
| Buongiorno Ltd | Hospitality | 2022 |
| Burlington Investments and Wealth Management Limited | Real estate | 2019 |
| Burshake Limited | Hospitality | 2024 |
| Business Energy Brokers Limited | Energy | 2017 |
| BUU Tours Ltd | Construction | 2025 |
| Buzzgloom Ltd | Information & communication | 2020 |
| BY Orzan Property Limited | Real estate | 2025 |
| Bymmk Ltd | Wholesale & retail | 2024 |
| Bysg Ltd | Construction | 2024 |