| Bille Transport Ltd | Transport & logistics | 2025 |
| Bilton Property (UK) Ltd | Real estate | 2011 |
| Bina Bhawan Limited | Health & social care | 2011 |
| Binary Gates Ltd | Information & communication | 2008 |
| Bingmon Limited | Wholesale & retail | 2023 |
| Binita's Beauty and Hair Salon Ltd | Other services | 2007 |
| Bipti Limited | Information & communication | 2025 |
| Birdfynn Accountants Ltd | Professional & scientific | 2021 |
| Birdwood Creative Ltd | Professional & scientific | 2019 |
| Birk Beck Costcutter Ltd | Wholesale & retail | 2017 |
| Biryani Villa Ltd | Hospitality | 2026 |
| Biryaniwala Wembley Ltd | Hospitality | 2026 |
| Bise Shipping Limited | Transport & logistics | 2025 |
| Bish 1 Limited | Construction | 2017 |
| Bishopswood Estates Limited | Construction | 1981 |
| Bison Property Ltd | Real estate | 2021 |
| BIT Forge Ltd | Information & communication | 2025 |
| Bite Bar Limited | Hospitality | 2015 |
| Bittreil Ltd | Information & communication | 2026 |
| BIZ Bloom Limited | Wholesale & retail | 2024 |
| BJK Building Services Ltd | Construction | 2015 |
| BK Bespoke Services Limited | Administrative & support | 2023 |
| BKP Design Concepts Ltd | Construction | 2014 |
| BL Joshi Holdings Limited | Financial services | 2002 |
| Black FOX One Ltd | Construction | 2014 |
| Black Furniture Limited | Wholesale & retail | 2025 |
| Black Gamma Ltd | Information & communication | 2015 |
| Black Knight Consultancy Ltd | Professional & scientific | 2019 |
| Black Pepper Consulting Limited | Professional & scientific | 2016 |
| Black Studios Ltd | Wholesale & retail | 2023 |
| Black TIE Investors Group Ltd | Real estate | 2023 |
| Black Wolf Motors Limited | Wholesale & retail | 2021 |
| Blackarrow Logistics Ltd | Transport & logistics | 2026 |
| Blackbird MOT Station Ltd | Administrative & support | 2016 |
| Blackeye Co & Sons Limited | Real estate | 2026 |
| Blackrose Corporation Limited | Professional & scientific | 1999 |
| Blackshell Limited | Real estate | 2019 |
| Blackstone Asset Holdings Ltd | Real estate | 2025 |
| Blackwood Consulting Limited | Professional & scientific | 2025 |
| Blackwood Group Holding Limited | Financial services | 2025 |
| Blackwood Investment Portfolio Ltd | Financial services | 2025 |
| Blades Crafts Ltd | Other services | 2023 |
| Blake Business Services Ltd | Administrative & support | 2026 |
| Blake's Mind Limited | Education | 2023 |
| Blandford Trading Ltd | Wholesale & retail | 2021 |
| Blank Canvas Fashion Limited | Manufacturing | 2024 |
| Blastoff AI Ltd | Information & communication | 2026 |
| Blaszczak Motors Ltd | Wholesale & retail | 2011 |
| Blink & Brow Ltd | Other services | 2018 |
| Blinks Bar Ltd | Other services | 2025 |
| Bliss & Bites Ltd | Hospitality | 2025 |
| Bliss Holistica Ltd | Health & social care | 2024 |
| Blockx AI Limited | Information & communication | 2025 |
| Blook Limited | Real estate | 2020 |
| Bloom & Glow CIC | Other services | 2025 |
| Bloom and Live Limited | Professional & scientific | 2018 |
| Bloomfield News Ltd | Wholesale & retail | 2021 |
| Blooming Bunches Limited | Wholesale & retail | 2025 |
| Bloomsbury Realty Ltd | Hospitality | 2020 |
| Blossom Life Care Limited | Health & social care | 2023 |
| Blossom Residence | Real estate | 2024 |
| Blossoms Kitchen Limited | Hospitality | 2017 |
| Blue Acorn Investments Ltd | Real estate | 2020 |
| Blue Akash Ltd | Information & communication | 2018 |
| Blue Bling Casting Agency Limited | Administrative & support | 2019 |
| Blue Bling Production House Limited | Information & communication | 2019 |
| Blue Brix Limited | Construction | 2024 |
| Blue Cat Trading Firm Ltd | Financial services | 2026 |
| Blue Cross Group Ltd | Wholesale & retail | 2019 |
| Blue Diamonds Limited | Financial services | 2006 |
| Blue Eyes UK Enterprises Ltd | Professional & scientific | 2012 |
| Blue Flag Publishing Limited | Information & communication | 1997 |
| Blue Green Europe Limited | Wholesale & retail | 2021 |
| Blue Hammock Limited | Professional & scientific | 2019 |
| Blue Horizon Media Promotions Limited | Administrative & support | 2016 |
| Blue Locus Limited | Health & social care | 2020 |
| Blue Lotus (Private) Limited | Real estate | 2025 |
| Blue Mercado Limited | Administrative & support | 2025 |
| Blue Mountain Ltd | Financial services | 2025 |
| Blue Ocean Pharma Limited | Professional & scientific | 2018 |
| Blue Ocean Waves Centre Ltd | Arts & recreation | 2021 |
| Blue Orchid Corporation Limited | Professional & scientific | 2011 |
| Blue Rider Group Ltd | Hospitality | 2019 |
| Blue Safire Ltd | Hospitality | 2013 |
| Blue Sea Quality Fish Ltd | Wholesale & retail | 2022 |
| Blue Slate Investment Ltd | Households | 2019 |
| Blue YAK Consulting Limited | Information & communication | 2012 |
| Bluebell Montessori School Limited | Education | 2015 |
| Bluebell Nursery Limited | Extraterritorial | 2011 |
| Blueberry Yolanda Letting Ltd | Hospitality | 2020 |
| Bluelattice.Io Ltd | Administrative & support | 2016 |
| Blueline Enterprise Limited | Construction | 2010 |
| Blueprint Build & Develop Ltd | Construction | 2026 |
| Blueprint Talent Ltd | Administrative & support | 2017 |
| Bluerentals Ltd | Hospitality | 2024 |
| Blueroot Investment Limited | Financial services | 2021 |
| Bluestream Consultancy Ltd | Administrative & support | 2012 |
| Blunham Court Management Company Limited | Households | 1964 |
| Blvck Enterprise Ltd | Hospitality | 2019 |
| Blvck Lounge Ltd | Manufacturing | 2019 |