| Best Value Price Limited | Wholesale & retail | 2025 |
| Beta Best Produce Ltd | Wholesale & retail | 2021 |
| Better Call SAM Ltd | Professional & scientific | 2024 |
| Better Fit Ltd | Professional & scientific | 2026 |
| Better Homes & Living Ltd | Real estate | 2023 |
| Beukes & Associates Ltd | Transport & logistics | 2018 |
| Bevel Building Ltd | Construction | 2018 |
| Bforte Limited | Real estate | 2022 |
| BG Garden Centre Limited | Agriculture & fishing | 2025 |
| Bglighting Limited | Information & communication | 2024 |
| BH Nail Salon Limited | Other services | 2022 |
| Bhandari Services Limited | Health & social care | 2023 |
| Bhatia Healthcare Ltd | Health & social care | 2024 |
| BHJ (Holdings) Limited | Professional & scientific | 2026 |
| Bhrm Limited | Households | 2018 |
| BIC Partnership Limited | Education | 2016 |
| BID4ABOAT Limited | Professional & scientific | 2024 |
| Big Green Carbon Cleaning Limited | Wholesale & retail | 2020 |
| Big Little Office Limited | Construction | 2009 |
| Bigm Real Estate Ltd | Real estate | 2024 |
| Bigstuff Limited | Manufacturing | 2003 |
| Bike Hutch Holdings Limited | Information & communication | 2017 |
| Billiter Street (1991) Limited | Professional & scientific | 1991 |
| Binary Balkara Limited | Information & communication | 2011 |
| Binder Bidco Limited | Professional & scientific | 2016 |
| Binder Holdco Limited | Financial services | 2016 |
| Binxatech Solutions Ltd | Wholesale & retail | 2024 |
| BIO Optimal Limited | Professional & scientific | 2014 |
| Bishops Waltham Removals Limited | Transport & logistics | 2001 |
| Bishopstoke Fishing Club Trustees Ltd | Arts & recreation | 2011 |
| Bishopstoke Tiling and Glazing Services | | 1989 |
| Bisley Business Services Ltd | Professional & scientific | 2009 |
| Bitterne Brickwork Ltd | Construction | 2022 |
| Bizjet Catering Ltd | Hospitality | 2022 |
| Bjmc Services Limited | Administrative & support | 2018 |
| Bjsn Ltd | Construction | 2024 |
| Bjszj Limited | Financial services | 2024 |
| BK Fresh Ltd | Professional & scientific | 2014 |
| BL Legal Limited | Professional & scientific | 2003 |
| Black Castle Homes Limited | Real estate | 2019 |
| Black Oak BBQ Ltd | Hospitality | 2025 |
| Blackburn Computing Limited | Information & communication | 2008 |
| Blackdown Garden Centre Limited | Wholesale & retail | 2009 |
| Blackhill Studios Limited | Information & communication | 2015 |
| Blacklava Solutions Limited | Arts & recreation | 2006 |
| Blackrock Yachting (Holdings) Limited | Financial services | 2025 |
| Blake Lapthorn Linnell Limited | Professional & scientific | 1994 |
| Blake Lapthorn LLP | | 2005 |
| Blake Lapthorn Nominees Limited | Administrative & support | 1994 |
| Blake Morgan Commercial Recoveries LLP | | 2014 |
| Blake Morgan Group LLP | | 2014 |
| Blake Morgan LLP | | 2014 |
| Blake Morgan Trustees Limited | Professional & scientific | 2004 |
| Blakedew 645 Limited | Administrative & support | 2006 |
| Blakelaw Director Services Limited | Administrative & support | 1985 |
| Blakelaw Secretaries Limited | Professional & scientific | 1985 |
| Blatchford Properties Limited | Real estate | 2019 |
| Blaze Construction Limited | Construction | 1991 |
| Blaze Plant Hire Limited | Administrative & support | 2020 |
| Blended Digital Ltd | Administrative & support | 2016 |
| Blossom and Green Ltd | Wholesale & retail | 2012 |
| Blosville Limited | Extraterritorial | 2022 |
| Blou Investments Ltd | Real estate | 2020 |
| Blou Ltd | Professional & scientific | 2010 |
| BLU Group Ltd | Extraterritorial | 2016 |
| BLU Marine Ltd | Manufacturing | 2007 |
| Blue Bear Aviation Limited | Manufacturing | 2018 |
| Blue Butterfly Dance Company Limited | Arts & recreation | 2018 |
| Blue Chilli Communications Limited | Professional & scientific | 2003 |
| Blue Dagger Ltd | Professional & scientific | 2013 |
| Blue Diamond Technologies Limited | Professional & scientific | 1978 |
| Blue Diamond UK Limited | Wholesale & retail | 1989 |
| Blue Diamond UK Properties Limited | Wholesale & retail | 1979 |
| Blue Drake Limited | Extraterritorial | 2014 |
| Blue Lamp Trust (Services) Ltd | Education | 2020 |
| Blue Mango Consulting Services Limited | Information & communication | 2007 |
| Blue Mist Properties Ltd | Real estate | 2022 |
| Blue Moggy Media Ltd | Information & communication | 2022 |
| Blue Viper Limited | Education | 2024 |
| Blue-Chips Services Limited | Information & communication | 2016 |
| Blueberry London Ltd | Wholesale & retail | 2016 |
| Blueberry ST Ives Limited | Wholesale & retail | 2021 |
| Bluebird Aviation Limited | Wholesale & retail | 2021 |
| Bluebox Vending Ltd | Wholesale & retail | 2025 |
| Bluecrown Ltd | Hospitality | 2023 |
| Bluekayn Limited | Construction | 2016 |
| Blueoak Property Care Ltd | Administrative & support | 2025 |
| Blueprint Media Holdings Limited | Financial services | 2023 |
| Blueprint Quantity Surveyors Ltd | Professional & scientific | 2026 |
| Bluewaters Properties Ltd | Real estate | 2022 |
| Blush Beauty and Hair Limited | Other services | 2026 |
| BM Removals and Storage Ltd | Transport & logistics | 2022 |
| BMS Build Ltd | Professional & scientific | 2026 |
| BN Legacy Projects Ltd | Construction | 2026 |
| BNN Commercial Limited | Real estate | 2022 |
| BNN Group Limited | Real estate | 2022 |
| BNN Residential Ltd | Real estate | 2022 |
| BNW Catering Ltd | Hospitality | 2019 |
| Boat Charter Ltd | Transport & logistics | 2021 |
| BOB Foster & Associates Ltd | Professional & scientific | 2004 |