| Biosync Limited | Manufacturing | 2024 |
| Biotsi Ltd | Wholesale & retail | 2026 |
| Birch Properties at Ltd | Real estate | 2024 |
| Bird Crowd Ltd | Professional & scientific | 2018 |
| Birdbox Software Ltd | Information & communication | 2026 |
| Birdie Breaks Limited | Administrative & support | 2024 |
| Birdspot Ltd | Professional & scientific | 2023 |
| Birling GAP Recruitment Limited | Administrative & support | 2018 |
| Birthchoiceuk Ltd | Information & communication | 2020 |
| Bishopsbury (Holdings) Limited | Other services | 1972 |
| BIT LUX Limited | Information & communication | 2021 |
| Bitecraft Dental LAB Ltd | Manufacturing | 2026 |
| Bitmorph Ltd | Information & communication | 2022 |
| Bitradex Fintech Limited | Financial services | 2025 |
| BITS4NET Ltd | Information & communication | 2012 |
| Bitsphere Consulting Ltd | Professional & scientific | 2024 |
| Bizanga Limited | Information & communication | 2004 |
| Bizbfriend Limited | Information & communication | 2015 |
| Bizdatas Ltd | Wholesale & retail | 2023 |
| Bizidentity Ltd | Information & communication | 2019 |
| Bizsolutionsbynilay Ltd | Professional & scientific | 2024 |
| Bizz Club London Ltd | Administrative & support | 2024 |
| BJH Property Limited | Real estate | 2023 |
| BK Legal and Claims Limited | Professional & scientific | 2025 |
| BK Research Limited | Administrative & support | 2022 |
| BKB Consultants Ltd | Information & communication | 2012 |
| BL12 Limited | Real estate | 2023 |
| Blabla Holdings Ltd | Financial services | 2017 |
| Black Ball Solutions Ltd | Information & communication | 2019 |
| Black Barn Commerce Limited | Information & communication | 2023 |
| Black Barrel Armouries Ltd | Manufacturing | 2022 |
| Black Bird Brewery Limited | Manufacturing | 2014 |
| Black Book Accounts Limited | Professional & scientific | 2008 |
| Black Bourn Vineyards Limited | Agriculture & fishing | 2020 |
| Black Cat Labs Ltd | Information & communication | 2025 |
| Black Drop Security Limited | Financial services | 2025 |
| Black FOX Finance Ltd | Financial services | 2020 |
| Black LAB Management Limited | Real estate | 2012 |
| Black Lake London Ltd | Transport & logistics | 2025 |
| Black Parents Together Ltd | Information & communication | 2024 |
| Black Smoke Consulting Limited | Professional & scientific | 2024 |
| Black Talon Ltd | Wholesale & retail | 2020 |
| Black Therapists Abroad Limited | Information & communication | 2025 |
| Blackbee Group Ltd | Professional & scientific | 2024 |
| Blackberry Group Limited | Construction | 2017 |
| Blackberry Investments Ltd | Real estate | 2019 |
| Blackbird & Wilde Coffeehouse Ltd | Hospitality | 2022 |
| Blackburn & Co Ltd | Manufacturing | 2014 |
| Blackdm Ltd | Information & communication | 2026 |
| Blackdown Medical Ltd | Education | 2025 |
| Blackdown Shire Ltd | Agriculture & fishing | 2026 |
| Blackline LDN Group Ltd | Water & waste | 2026 |
| Blackman Associates Limited | Information & communication | 2000 |
| Blackpool B&B Limited | Hospitality | 2018 |
| Blackq.Tv Limited | Arts & recreation | 2020 |
| Blackridge Cloud Ltd | Information & communication | 2025 |
| Blackshield Services Ltd | Administrative & support | 2025 |
| Blackstone Construction Ltd | Construction | 2026 |
| Blackwoods Group Ltd | Financial services | 2025 |
| Blade Software Limited | Information & communication | 2002 |
| Blakenham Park (Ipswich) Management Company Limited | Households | 2005 |
| Blanchard Property Services Limited | Real estate | 2026 |
| Blank Creative Services Ltd | Information & communication | 2026 |
| Blayze Tech Limited | Manufacturing | 2020 |
| BLB Consultancy Ltd | Professional & scientific | 2023 |
| Blenzo ENT Limited | Wholesale & retail | 2023 |
| Bless Autos Ltd | Transport & logistics | 2024 |
| Blessed Essentials Ltd | Wholesale & retail | 2026 |
| Blessing Abode Ltd | Hospitality | 2024 |
| Blessing Mankind Community Development Ministries Ltd | Other services | 2020 |
| Bleuglobal Ltd | Wholesale & retail | 2025 |
| Blimp Creative Ltd | Information & communication | 2014 |
| Blissful Decor Ltd | Administrative & support | 2023 |
| Blissful Solutions Ltd | Administrative & support | 2025 |
| Blkn Muscle Ltd | Wholesale & retail | 2024 |
| Blmbrg Limited | Professional & scientific | 2021 |
| Block Coaching Ltd | Arts & recreation | 2026 |
| Block Security Ltd | Information & communication | 2014 |
| Blockfusion Insight Ltd | Information & communication | 2026 |
| Bloclogic Ltd | Information & communication | 2019 |
| Blomberg Ltd | Professional & scientific | 2016 |
| Bloom and Flow Limited | Wholesale & retail | 2024 |
| Bloomfield Accountancy Limited | Professional & scientific | 2020 |
| Bloomfield Partners Ltd | Professional & scientific | 2012 |
| Bloomycraft Labs Ltd | Information & communication | 2026 |
| Blossom Educational Psychology Limited | Professional & scientific | 2021 |
| Blossoming Care Ltd | Health & social care | 2024 |
| Blossoming Child Psychology Ltd | Education | 2024 |
| Blossomingwomen Ltd | Education | 2023 |
| BLU Pack Group Limited | Financial services | 2024 |
| Blubelle Beauté Ltd | Other services | 2024 |
| Blue Apatite Consulting Ltd | Professional & scientific | 2017 |
| Blue Arrow Group Ltd | Hospitality | 2026 |
| Blue Bridge Software Limited | Information & communication | 2024 |
| Blue Bubble Ltd | Manufacturing | 2021 |
| Blue Dolphin Express Limited | Transport & logistics | 2025 |
| Blue Dome Education Ltd | Education | 2025 |
| Blue FIG (Bury) Ltd | Hospitality | 2025 |
| Blue Flag Services Ltd | Administrative & support | 2017 |
| Blue Foresight Advisory Ltd | Administrative & support | 2025 |