| Big Red EGG Ltd | Wholesale & retail | 2015 |
| Big Shoulders Ltd | Professional & scientific | 2019 |
| Big Transform Limited | Professional & scientific | 2014 |
| Bigfoot International Education Ltd | Education | 2013 |
| Bigkid Limited | Wholesale & retail | 2000 |
| Biliks London Limited | Wholesale & retail | 2016 |
| Bill Harvest Limited | Professional & scientific | 2012 |
| Billionaire Estates Limited | Professional & scientific | 1997 |
| Bimcert Ltd | Professional & scientific | 2014 |
| BIN Aman Perfumes UK Limited | Wholesale & retail | 2025 |
| Bindon Property Ltd | Real estate | 2017 |
| Bingham Hotel & Restaurant Ltd | Hospitality | 2010 |
| Bingos International Education Ltd. | Education | 2018 |
| Binisang Limited | Construction | 2024 |
| Binji TM Limited | Construction | 2026 |
| BIO Movement Ltd | Health & social care | 2023 |
| BIO Pharma Resourcing Ltd | Administrative & support | 2005 |
| Biodiversity Conservation Services Ltd | Professional & scientific | 2024 |
| Bioemulous Limited | Wholesale & retail | 2014 |
| Biolena Aesthetics Ltd | Other services | 2024 |
| Bios Healing Therapies Limited | Health & social care | 2018 |
| Biosolve Consulting Ltd | Professional & scientific | 2021 |
| Birch Creative Design Limited | Professional & scientific | 2019 |
| Birchman ESP Limited | Professional & scientific | 2003 |
| Birdbox Developments Limited | Construction | 2024 |
| Birdbox Properties Limited | Construction | 2021 |
| Birmingham Hotel Limited | Hospitality | 2009 |
| Bishop's Close Management Company Limited | Households | 1984 |
| Bishopsgate 109 Limited | Real estate | 2023 |
| Bita Holdings Limited | Financial services | 2022 |
| Bizibot Productions Limited | Information & communication | 2005 |
| Bizsoft Technologies Limited | Information & communication | 2022 |
| Blacbird Ltd. | Professional & scientific | 2025 |
| Black Gold Films Limited | Extraterritorial | 2021 |
| Black Lion Finkle Street Limited | Hospitality | 2022 |
| Black Mesa Engineering Limited | Construction | 2024 |
| Blackbird Engineering Ltd | Professional & scientific | 2021 |
| Blackbird Rise Ltd | Administrative & support | 2025 |
| Blackbox Productions UK Ltd | Information & communication | 2009 |
| Blackett (UK) Limited | Information & communication | 1964 |
| Blackheath Properties Limited | Administrative & support | 1995 |
| Blasta Henriet Ltd | Manufacturing | 2017 |
| Blaygrove Ellis Limited | Professional & scientific | 1987 |
| Blazher Ltd | Wholesale & retail | 2022 |
| Blessed DEW Ltd | Hospitality | 2025 |
| Bliss Health Limited | Professional & scientific | 2004 |
| Blockmart Limited | Real estate | 1990 |
| Blockskye Limited | Administrative & support | 2026 |
| Bloomfield Life Ltd | Administrative & support | 2024 |
| Blooms of London Ltd | Manufacturing | 2009 |
| Bloomsbury International Training Academy (B.I.T.A.) Ltd | Information & communication | 2023 |
| BLU Family Office Limited | Financial services | 2015 |
| Blue Anchor Projects Ltd | Information & communication | 2017 |
| Blue Bull Ltd | Information & communication | 2013 |
| Blue Car Technologies Limited | Information & communication | 2007 |
| Blue Change Consultancy Ltd | Information & communication | 2024 |
| Bluedog Bear Limited | Professional & scientific | 2024 |
| Bluejoy Ltd | Education | 2015 |
| Bluespike Landscape Designs Ltd | Administrative & support | 2007 |
| Blustaff Properties Limited | Real estate | 2024 |
| Bluu Consulting Limited | Professional & scientific | 2006 |
| BMG Holding Group Limited | Financial services | 2023 |
| BML Management Ltd | Other services | 2003 |
| BOA Boutique Limited | Wholesale & retail | 2011 |
| Boardworth Limited | Other services | 2018 |
| BOB Associates Ltd | Professional & scientific | 2020 |
| Bodmyn Investments Limited | Administrative & support | 2010 |
| Body Religion Ltd | Professional & scientific | 2016 |
| Bodydoctor Interactive Limited | Arts & recreation | 2008 |
| Bodyfirm Ltd | Other services | 2020 |
| Bodylistics Ltd | Health & social care | 2014 |
| Bokelmann Advisors Ltd | Professional & scientific | 2025 |
| Bold Innovate Ltd | Information & communication | 2024 |
| Bold Leap Consulting Limited | Professional & scientific | 2015 |
| Bolder Brands Limited | Professional & scientific | 2020 |
| BON Coeur Fine Wines Limited | Wholesale & retail | 2005 |
| Bonacom Ltd | Real estate | 2022 |
| Bond Venture Investments Ltd | Professional & scientific | 2011 |
| Bonfiglioli Advisory Limited | Professional & scientific | 2017 |
| Bonum Estates Ltd | Real estate | 2024 |
| Book an Occasion Limited | Administrative & support | 2021 |
| Bookingtek Limited | Administrative & support | 2011 |
| Books on the Rise Limited | Wholesale & retail | 2022 |
| Boom Innovation Limited | Arts & recreation | 2008 |
| Boroleigh Limited | Manufacturing | 2025 |
| Bosanquet Limited | Other services | 2024 |
| Boscar Limited | Real estate | 2012 |
| Boss & Co.Limited | Manufacturing | 1967 |
| Botanic Gardens Conservation International | Other services | 2003 |
| Boundlessly FUN Ltd | Administrative & support | 2022 |
| Boutique Design Limited | Professional & scientific | 2004 |
| Bouwmeester Consulting Engineers Limited | Construction | 2017 |
| Bowecliff Limited | Households | 2008 |
| Bowers Developments Ltd | Real estate | 2013 |
| Bowman Builders Limited | Construction | 2006 |
| Boyport Services Limited | Arts & recreation | 2002 |
| Boyureco Limited | Administrative & support | 2007 |
| Bpce Equipment Solutions UK (December) Limited | Financial services | 1980 |
| Bpce Equipment Solutions UK Limited | Financial services | 1998 |
| BPI News Ltd | Information & communication | 2015 |