| Bluesun 2001 Limited | Professional & scientific | 2024 |
| BLY Contracting Ltd | Construction | 2020 |
| Blythe Solutions Consultancy Ltd | Administrative & support | 2023 |
| BM Motorsports Ltd | Wholesale & retail | 2016 |
| BM Technical Limited | Construction | 2016 |
| BMS Leak Detection Ltd | Construction | 2018 |
| BNK2 Ltd | Real estate | 2024 |
| Bobandalf Ltd | Professional & scientific | 2021 |
| BOC Mechanical and Electrical Services Limited | Construction | 2025 |
| Body Ethics Academy Limited | Arts & recreation | 2020 |
| Body Ethics Limited | Arts & recreation | 2019 |
| Bohemia's Closet Ltd | Wholesale & retail | 2017 |
| Boilerpoint Ltd | Construction | 2021 |
| Bokeh Digital Limited | Information & communication | 2019 |
| Bolam Consultancy Limited | Health & social care | 2009 |
| Bold and Noble Limited | Wholesale & retail | 2008 |
| Bombay WOK Limited | Hospitality | 2025 |
| Bond Patrick Ltd | Professional & scientific | 2021 |
| Bonum Safety Services Limited | Education | 2018 |
| Boozypuds Limited | Wholesale & retail | 2026 |
| Boreoak Limited | Professional & scientific | 2017 |
| Boss Tuning Ltd | Wholesale & retail | 2021 |
| Bostech Innovations Ltd | Extraterritorial | 2024 |
| Boulevard Trading Ltd | Wholesale & retail | 2022 |
| Bowen Dawes LLP | | 2019 |
| Bowmans Associates Limited | Real estate | 2004 |
| Box Bike Delivery LLP | | 2014 |
| Boxall Taxis Ltd | Transport & logistics | 2005 |
| Bracey's Accountants (Audit) Limited | Professional & scientific | 2018 |
| Bracey's Accountants (MK) Limited | Professional & scientific | 2022 |
| Bracey's Accountants (Tax & VAT) Limited | Professional & scientific | 2018 |
| Bracey's Accountants Ltd | Professional & scientific | 2010 |
| Bracey's Financial Services LLP | | 2024 |
| Braceypg Limited | Financial services | 2020 |
| Braceys Motors Limited | Wholesale & retail | 2020 |
| Bracey’S Accountants (ST Albans) Limited | Extraterritorial | 2024 |
| Bracey’S BPO LLP | | 2026 |
| Bracey’S Consulting Limited | Professional & scientific | 2013 |
| Bradshaw Johnson Limited | Professional & scientific | 1980 |
| Bradshaw Johnson Secretarial Limited | Professional & scientific | 2002 |
| Brampton Park Surveying Limited | Professional & scientific | 2016 |
| Brand by ME Limited | Professional & scientific | 2016 |
| Brandables Ltd | Professional & scientific | 2008 |
| Braven Consulting Ltd | Professional & scientific | 2010 |
| Breachwood Green Ltd | Other services | 2020 |
| Break Free Consulting Ltd | Administrative & support | 2023 |
| Brew Retail 2 Limited | Hospitality | 2025 |
| Brew Retail 3 Limited | Hospitality | 2025 |
| Brew Retail 4 Limited | Hospitality | 2025 |
| Brew Retail Limited | Hospitality | 2025 |
| Brewman Enterprises Limited | Hospitality | 1988 |
| Brian Woodhead Consulting Ltd | Professional & scientific | 2021 |
| Brick and Key Ltd | Real estate | 2019 |
| Brick Architects Ltd | Professional & scientific | 2017 |
| Bricks and Flips Property Ltd | Real estate | 2019 |
| Bricks and More Property Ltd | Real estate | 2018 |
| Bridal Bounty Catering Ltd | Hospitality | 2025 |
| Bride Hall Developments Ltd | Construction | 2014 |
| Bridge Fibre Limited | Information & communication | 2001 |
| Bridge Street Management Company (Hitchin) Limited | Households | 2015 |
| Bridgewood Wellness Limited | Health & social care | 2020 |
| Brielle Property Management Ltd | Real estate | 2019 |
| Bright Future Fundraising Limited | Other services | 2020 |
| Brighter Homes (Herts) Limited | Real estate | 2024 |
| Brighter Stays Care Limited | Health & social care | 2024 |
| Brighter Stays Limited | Public administration | 2021 |
| Brilink Limited | Extraterritorial | 2004 |
| Brills Services Limited | Hospitality | 2024 |
| British Activity Providers Association | Other services | 1990 |
| British Science Fiction Association Limited(The) | Other services | 1967 |
| British Show Horse Association | Arts & recreation | 2001 |
| Brittain Properties Ltd | Real estate | 2018 |
| Britztrends Limited | Wholesale & retail | 2025 |
| Brmt Assets Limited | Real estate | 2023 |
| Brmt Properties Limited | Real estate | 2023 |
| Broadview Holdings Limited | Real estate | 2020 |
| Broadview Windows Limited | Construction | 2001 |
| Brockmore Sales and Lettings Limited | Real estate | 2020 |
| Broman Properties Ltd | Real estate | 2021 |
| Bronze Monkey Limited | Arts & recreation | 2014 |
| Brook View Plumbing and Property Services Limited | Construction | 2020 |
| Brookbank IND. Automation & Controls Ltd | Professional & scientific | 2011 |
| Brooke Bohan Limited | Other services | 2024 |
| Brookend Plant Limited | Administrative & support | 2022 |
| Brooks Swim School Ltd | Education | 2019 |
| Brotin Soul Limited | Real estate | 2022 |
| Brown & Gammons Limited | Wholesale & retail | 1977 |
| Brown & Green Research Limited | Construction | 2013 |
| Brown Marine Legal Limited | Professional & scientific | 2015 |
| Browns Care Limited | Health & social care | 2022 |
| BRP Health Ltd | Health & social care | 2022 |
| Bruce Langlands & Associates Limited | Professional & scientific | 2022 |
| Bruce Sawford Licensing Limited | Information & communication | 2004 |
| Bryan Investments Limited | Real estate | 2021 |
| Bssm Ltd | Real estate | 1971 |
| BTB Recruitment Limited | Administrative & support | 2005 |
| BTE Capital Limited | Real estate | 2025 |
| BTM Projects Limited | Real estate | 2012 |
| BTS1 Ltd | Construction | 2025 |
| Btsg Property Services Ltd | Financial services | 2025 |