| Berryman Environmental Limited | Administrative & support | 2001 |
| Berymol Limited | Professional & scientific | 2017 |
| Bespoke Event Team Ltd | Arts & recreation | 2013 |
| Bespoke Garden Projects Limited | Administrative & support | 2021 |
| Bespoke Plastic Surgery Limited | Health & social care | 2008 |
| Best Miller LLP | | 2025 |
| Best Mortgage Product Ltd | Financial services | 2019 |
| Best Practice Academy Ltd | Financial services | 2020 |
| Beta Safety Systems Limited | Construction | 2004 |
| Bethan Williams Ltd | Health & social care | 2013 |
| Better Home Living Concepts Limited | Wholesale & retail | 2022 |
| Better Sales Ltd | Professional & scientific | 2023 |
| Betty's Pet Supplies Limited | Wholesale & retail | 2024 |
| Beverage Equipment Supplies Limited | Administrative & support | 2012 |
| Beyond Cocktails Ltd | Hospitality | 2024 |
| Bfom Limited | Financial services | 2016 |
| BFORTUNE8 Ltd | Other services | 2018 |
| Bfrank Ltd | Health & social care | 2025 |
| BG Construction S.E. Limited | Construction | 2009 |
| Bgcr Limited | Households | 2019 |
| Bhagani Properties Ltd | Real estate | 2020 |
| Big Gofer Ltd | Administrative & support | 2022 |
| Big Little Book Swap Ltd | Wholesale & retail | 2026 |
| Big Picture Insight Ltd | Other services | 2023 |
| Big Wave Digital Limited | Professional & scientific | 2023 |
| Bikenation MCS Limited | Wholesale & retail | 2010 |
| Bill Bruford Productions Limited | Arts & recreation | 1972 |
| Bill the Grip Ltd | Construction | 2025 |
| Billex Consulting Limited | Information & communication | 2022 |
| Billie Vinue Limited | Other services | 2016 |
| Billsallincluded Property Management Ltd | Real estate | 2017 |
| Billy Goat Shoes Limited | Wholesale & retail | 2015 |
| Binfields Management Company Limited | Households | 1986 |
| Binsted Group Limited | Information & communication | 1997 |
| Binsted Publications Limited | Extraterritorial | 1992 |
| Biodivercity Associates Limited | Professional & scientific | 2011 |
| Birch Meadow Management Company Limited | Households | 2001 |
| Birches Management Company Limited(The) | Households | 1979 |
| Birchwood Landscaping and Outdoor Living Limited | Administrative & support | 2025 |
| Birmingham Stamping Ltd | Manufacturing | 2023 |
| Bizmosis Ltd | Professional & scientific | 2006 |
| Bizskill Limited | Information & communication | 1984 |
| Bizzy BEE General Maintenance Limited | Administrative & support | 2006 |
| BKS Business Services Ltd | Professional & scientific | 2024 |
| BL Aviation Consultancy Ltd | Wholesale & retail | 2025 |
| BLA Ventilation Limited | Manufacturing | 2018 |
| Black Book Wealth Ltd | Professional & scientific | 2026 |
| Black Crow Estates Limited | Real estate | 1996 |
| Black HAT Consulting Ltd. | Professional & scientific | 2012 |
| Black Honey Cafe Ltd | Administrative & support | 2023 |
| Blackbird Rook Ltd | Wholesale & retail | 2024 |
| Blackcrest Eagle Ltd | Wholesale & retail | 2025 |
| Blacknest (2016) Property Company Limited | Real estate | 2016 |
| Blackstock Architecture Ltd | Professional & scientific | 2021 |
| Blackstone Koala Limited | Professional & scientific | 2023 |
| Blackwater Estates Management Ltd | Construction | 2019 |
| Blackwater Ltd | Information & communication | 2024 |
| Blackwood & SON Engineering Ltd | Professional & scientific | 2019 |
| Bladeoffire Limited | Other services | 2003 |
| Blaise & Wilder Limited | Wholesale & retail | 2024 |
| Blcn Property Ltd | Real estate | 2025 |
| Blenheim Building Services Limited | Construction | 2011 |
| Blenheim Construction Limited | Construction | 2014 |
| Blenheim Court (Fleet) Management Company Limited | Households | 2001 |
| Blenheim Health Safety & Environmental Limited | Health & social care | 2019 |
| Blenheim Holdings South Limited | Real estate | 2019 |
| Blenheim Holdings Southern Limited | Construction | 2019 |
| Blenheim Lets Limited | Real estate | 2022 |
| Blenheim Mews Flats Limited | Households | 2010 |
| Blightman Consultancy Limited | Information & communication | 2011 |
| Blncd Drinks Ltd | Wholesale & retail | 2024 |
| Bloc Developments Limited | | 2007 |
| Blocarc Trading Limited | Construction | 2003 |
| Bloctave Ltd | Information & communication | 2024 |
| Blond Consulting Limited | Financial services | 2010 |
| Blond Property Limited | Real estate | 2022 |
| Bloodbuzz Ltd | Manufacturing | 2025 |
| BLU Development and Renovations Limited | Construction | 2019 |
| Blubright Property Ltd | Real estate | 2025 |
| Blue 8 Consulting Ltd | Professional & scientific | 2023 |
| Blue BAT Solutions Ltd | Professional & scientific | 2025 |
| Blue Butterfly Consulting Limited | Wholesale & retail | 2014 |
| Blue Cedar Software Limited | Information & communication | 2018 |
| Blue Dog Productions Limited | Administrative & support | 2020 |
| Blue Door Consultancy Ltd | Education | 2025 |
| Blue Fern Consult Ltd | Professional & scientific | 2020 |
| Blue Flamingo Digital Limited | Wholesale & retail | 2021 |
| Blue Mozaic Limited | Professional & scientific | 2023 |
| Blue Petrel Consulting Limited | Administrative & support | 2010 |
| Blue Star Commercial Gardens Limited | Administrative & support | 1996 |
| Blue Tiger Boutique Ltd | Wholesale & retail | 2024 |
| Blue Weasel Books Ltd | Information & communication | 2021 |
| Bluebelle Designs Limited | Arts & recreation | 2012 |
| Blueberry Hill Holdings Limited | Professional & scientific | 2020 |
| Bluebird Psychology Ltd | Health & social care | 2025 |
| Bluedog International Holdings Limited | Financial services | 2023 |
| Bluefish PR Limited | Professional & scientific | 2013 |
| Blueharbour Enterprises Ltd | Real estate | 2025 |
| Bluelemon Holdings Limited | Real estate | 2023 |
| Bluespoon Studios Ltd | Information & communication | 2022 |