| Biomass Partners UK Limited | Administrative & support | 2013 |
| Biome Technology Group Ltd | Information & communication | 2025 |
| Biomedical Science LAB Limited | Professional & scientific | 2025 |
| Biomondia Ltd | Wholesale & retail | 2019 |
| Bionica Ltd | Information & communication | 2021 |
| Bionox Ltd | Professional & scientific | 2012 |
| Biorecycling Logistics Limited | Professional & scientific | 2011 |
| Biorik Ltd | Wholesale & retail | 2025 |
| Biostart Ltd | Administrative & support | 2021 |
| Biostrand Limited | Wholesale & retail | 2025 |
| Biosyn Limited | Wholesale & retail | 2025 |
| Biotec Evolution Ltd | Professional & scientific | 2020 |
| Biotec Services International Limited | Administrative & support | 1997 |
| Biotech Brands Ltd | Wholesale & retail | 2017 |
| Bioticnrg 2 Co-Invest L.P. | | 2026 |
| Bioticnrg 2 L.P. | | 2026 |
| Bioxane Ltd | Wholesale & retail | 2018 |
| Biozone Scientific (UK) Ltd | Wholesale & retail | 2005 |
| Biozone Scientific Group Limited | Financial services | 2020 |
| Bipe Consulting Ltd | Education | 2023 |
| Bipsync UK Limited | Information & communication | 2013 |
| Biqin Business Limited | Wholesale & retail | 2024 |
| Birch EU VEL Ltd | Information & communication | 2025 |
| Birch Grove Service and Repair Ltd | Wholesale & retail | 2023 |
| Birch Legal Services Ltd | Professional & scientific | 2021 |
| Birchall Consulting Services Limited | Professional & scientific | 2016 |
| Birchcourt Limited | Health & social care | 2006 |
| Birchgood Limited | Health & social care | 2015 |
| Birchgrove Car Services Ltd | Wholesale & retail | 2025 |
| Birchgrove Hand Car Wash Limited | Administrative & support | 2023 |
| Birchwood Health Limited | Health & social care | 2004 |
| Birchwood Motors Ltd | Wholesale & retail | 2022 |
| Bird EDU Overseas Ltd | Administrative & support | 2023 |
| Bird EYE Books Limited | Information & communication | 2019 |
| Birdbox Commercial Limited | Professional & scientific | 2018 |
| Birdhaus Restaurants Ltd | Hospitality | 2020 |
| Birds Wings Ltd | Wholesale & retail | 2025 |
| Birgham Bidco Limited | Financial services | 2026 |
| Birgham Midco 1 Limited | Financial services | 2026 |
| Birgham Midco 2 Limited | Financial services | 2026 |
| Birgham Topco Limited | Financial services | 2026 |
| Birkale ASH Ltd | Wholesale & retail | 2022 |
| Birling Management (UK) Ltd | Professional & scientific | 2016 |
| Birmingham & Midlands Relocation Service Ltd | Hospitality | 2020 |
| Birnie Oral Surgery Ltd | Health & social care | 2019 |
| Birthearthsolar Limited | Construction | 2025 |
| Bisawer Ltd | Wholesale & retail | 2025 |
| Bish Bash Bosh Marketing Limited | Professional & scientific | 2020 |
| Bishop Contractors Limited | Construction | 2026 |
| Bishops Court Brecon RTM Company Limited | Households | 2023 |
| Bishops Gate (Cardiff) Management Limited | Households | 2004 |
| Bismiltrader Limited | Wholesale & retail | 2025 |
| Bisoma Ltd | Wholesale & retail | 2026 |
| Bissan Ltd | Hospitality | 2022 |
| BIT Byte Network (UK) Limited | Information & communication | 2020 |
| BIT Healthcare Services Ltd | Administrative & support | 2018 |
| BIT Insighters Technologies Ltd | Wholesale & retail | 2026 |
| BIT Services T Ltd | Transport & logistics | 2019 |
| BIT Systems Limited | Information & communication | 1994 |
| Bit's Repair Ltd | Construction | 2026 |
| Bitbankers Investment Ltd | Financial services | 2024 |
| Bitbros-Uk Ltd | Information & communication | 2024 |
| Bitcetus Digital Assets Investment Management Ltd | Information & communication | 2022 |
| Bitcoin Banque Ltd | Financial services | 2019 |
| Bitcorp Ltd | Wholesale & retail | 2025 |
| Bitdu Limited | Financial services | 2020 |
| Bitesuk Limited | Wholesale & retail | 2024 |
| Bitex-It Limited | Information & communication | 2019 |
| Bitfate Limited | Wholesale & retail | 2025 |
| Bitguru PC | | 2018 |
| Bithold Ltd | Financial services | 2021 |
| Bitio Limited | Information & communication | 2025 |
| Bitlume Ltd | Wholesale & retail | 2025 |
| Bitopia Ltd | Financial services | 2018 |
| Bitrade Ltd | Financial services | 2020 |
| Bits & NIX Limited | Wholesale & retail | 2020 |
| Bits Collection Limited | Other services | 2017 |
| Bits to Volts Ltd | Professional & scientific | 2021 |
| Bits.Buy Ltd | Wholesale & retail | 2019 |
| Bitvestor Limited | Hospitality | 2025 |
| Bitwild Ltd | Information & communication | 2008 |
| Bitwoven Ltd | Information & communication | 2024 |
| Bitwrite Limited | Information & communication | 2025 |
| Bitz & Bytes Ltd | Information & communication | 2019 |
| BIZ Print Solutions Limited | Manufacturing | 2018 |
| BIZ Sportswear Ltd | Wholesale & retail | 2016 |
| Bizabiza Ltd | Hospitality | 2025 |
| Bizacademy Ltd | Information & communication | 2025 |
| Bizau Utilities Ltd | Construction | 2023 |
| Bizbackerz Ltd | Information & communication | 2024 |
| Bizel Art Limited | Arts & recreation | 2026 |
| Bizguru Consulting Ltd | Other services | 2019 |
| Bizsella Ltd | Wholesale & retail | 2017 |
| Bizspoke Ltd | Information & communication | 2016 |
| Bizzboost Media Limited | Other services | 2024 |
| BJ Telecoms Ltd | Construction | 2024 |
| BJH Locum Services Ltd | Health & social care | 2023 |
| BJJ247 Events Ltd | Arts & recreation | 2015 |
| Bjmd Holdings Ltd | Hospitality | 2026 |
| BJO Properties Limited | Real estate | 2021 |