| Bibimoney Ltd | Information & communication | 2014 |
| BIC (Business Intelligence Consulting) Limited | Information & communication | 2018 |
| Bicc Components Limited | Professional & scientific | 2008 |
| Bier Nuts Limited | Hospitality | 2017 |
| Biezentec Ltd | Information & communication | 2019 |
| Bifolds NOW Limited | Construction | 2018 |
| Big 4 Consultancy Limited | Real estate | 2011 |
| Big Break Promotions Ltd | Arts & recreation | 2020 |
| Big Drilla Ltd | Wholesale & retail | 2025 |
| Big Shoe Property Ltd | Real estate | 2025 |
| Big Swift Limited | Financial services | 2022 |
| Big Van MAN Watford Ltd | Transport & logistics | 2024 |
| Big Ventures Limited | Wholesale & retail | 2025 |
| Big Yellow Tree Limited | Wholesale & retail | 2017 |
| Bigben Care Ltd | Health & social care | 2021 |
| Bigdoor Properties Limited | Construction | 2018 |
| Bigfoot Blossoms Limited | Construction | 2018 |
| Biggy Courier Ltd | Transport & logistics | 2025 |
| Bigkicks Limited | Extraterritorial | 2002 |
| Bigmantra Ltd | Information & communication | 2009 |
| Bigwood Court Management Limited | Real estate | 1993 |
| Bigyem Ltd | Administrative & support | 2013 |
| Bilal Travel Agency Ltd | Administrative & support | 2020 |
| Billet Court (Berkhamsted) Management Company Limited | Households | 1976 |
| Bills Included Limited | Real estate | 2024 |
| Billy Currell the Roofing Specialist Limited | Administrative & support | 2012 |
| Bima Holdings Limited | Financial services | 2021 |
| Bimar Properties Ltd | Construction | 2025 |
| Bimarem Ltd | Wholesale & retail | 2025 |
| Binary Thinkers Ltd | Information & communication | 2016 |
| Bindiya Vogue Limited | Real estate | 2017 |
| Bingo Bango Bosh Limited | Information & communication | 2014 |
| Biniti Consulting Ltd | Professional & scientific | 2025 |
| BIO CBD UK Limited | Health & social care | 2018 |
| BIO Cosmetics UA Ltd | Wholesale & retail | 2014 |
| Bio-Metrics (U.K.) Limited | Professional & scientific | 1990 |
| Bio-Rad Laboratories Limited | Wholesale & retail | 1995 |
| Bio-Rad Services UK Limited | Administrative & support | 2016 |
| Biobos Limited | Wholesale & retail | 2014 |
| Biogreen Innovations Ltd | Wholesale & retail | 2025 |
| Biopaxium Technologies Limited | Manufacturing | 2014 |
| Biotech Insights Limited | Information & communication | 2025 |
| Biovacc Consulting Limited | Professional & scientific | 2016 |
| Birchill Music (Holdings) Limited | Financial services | 2024 |
| Birchill Music Limited | Arts & recreation | 1977 |
| Birchill Music Projects (Holdings) Limited | Financial services | 2024 |
| Birchill Music Projects Limited | Information & communication | 2024 |
| Birchstone Care Homes Ltd | Financial services | 2022 |
| Birds EYE Care Services Limited | Administrative & support | 2025 |
| Birds EYE Consultants Limited | Wholesale & retail | 2026 |
| Birds Hill Management Limited | Households | 2006 |
| Birkett Commercial Limited | Professional & scientific | 2017 |
| Biryani Bytes Limited | Hospitality | 2020 |
| Biryani House Ltd | Hospitality | 2026 |
| Biryani Longue Ltd | Hospitality | 2025 |
| Bishan Shah Ltd | Wholesale & retail | 2016 |
| Bishop Investments Ltd | Professional & scientific | 2016 |
| Bishop's Place (Hatfield) Management Company Limited | Households | 2004 |
| Bishopsgate Business Solutions Ltd | Professional & scientific | 2012 |
| Bismillah Barbers Ltd | Other services | 2019 |
| Bispecialists Ltd | Information & communication | 2008 |
| Bite Lite Limited | Hospitality | 2025 |
| Bitmech Ltd | Information & communication | 2026 |
| Bitnosis Limited | Information & communication | 2013 |
| Bito's Service Ltd | Wholesale & retail | 2018 |
| Bitsmiths Ltd | Information & communication | 2018 |
| Bitvu Limited | Information & communication | 2010 |
| Bixbox Limited | Wholesale & retail | 2026 |
| Bizadept Consulting Limited | Professional & scientific | 2007 |
| Bizo Ltd | Other services | 2023 |
| Biztrans Consulting Services Ltd | Information & communication | 2023 |
| BJB 1974 Limited | Administrative & support | 2012 |
| BJC Consultancy Limited | Professional & scientific | 2023 |
| Bjiaf Ltd. | Professional & scientific | 2019 |
| BK Housing Support C.I.C. | Real estate | 2024 |
| BK Recovery & Transport Ltd | Wholesale & retail | 2026 |
| Bkaria Limited | Information & communication | 2021 |
| Bkmb Construction Ltd | Construction | 2023 |
| BKN Cassiobury Ltd | Real estate | 2023 |
| BL (Chesterfield) Limited | Construction | 2014 |
| BL Prime Properties Limited | Real estate | 2017 |
| Black Box Magic Ltd | Professional & scientific | 2008 |
| Black Box Security UK Ltd | Transport & logistics | 2020 |
| Black British Hearts Limited | Education | 2015 |
| Black Cat Holdings Ltd | Financial services | 2023 |
| Black Coyote Limited | Wholesale & retail | 2012 |
| Black Danda Ltd | Arts & recreation | 2025 |
| Black Deer Entertainment Ltd | Information & communication | 2022 |
| Black Eagle IT Ltd | Professional & scientific | 2024 |
| Black Girl Finance Limited | Education | 2019 |
| Black Hawk Site Engineering Ltd | Construction | 2016 |
| Black LAB (DI) Limited | Information & communication | 2019 |
| Black LAB Ltd | Health & social care | 2025 |
| Black Oak Assets Limited | Real estate | 2022 |
| Black Razor Records Ltd | Information & communication | 2024 |
| Black Sea 1913 Ltd | Other services | 2022 |
| Black VFX Limited | Information & communication | 2014 |
| Blackbird Freehold Management Ltd | Households | 2022 |
| Blackeaglehousing Ltd | Real estate | 2026 |
| Blackfeather Properties Limited | Real estate | 2025 |