| Bonny Limited | Manufacturing | 2021 |
| Bonus Ball Holidays Ltd | Extraterritorial | 2020 |
| Boogie Woogie Limited | Information & communication | 2007 |
| Book a Model Limited | Administrative & support | 2017 |
| Boostpiece Limited | Real estate | 2002 |
| Borbil Construction Ltd | Construction | 2017 |
| Borehamwood Food Centre Ltd | Wholesale & retail | 2025 |
| Borehamwood Luggage Ltd | Wholesale & retail | 2025 |
| Borun Studios Ltd | Information & communication | 2025 |
| Bosco Design Ltd | Construction | 2018 |
| Bosmend Limited | Professional & scientific | 2021 |
| BOTANICA24 Limited | Real estate | 2024 |
| Boudjnah Real Estate Limited | Real estate | 2020 |
| Bougie Beigel Ltd | Hospitality | 2025 |
| Bowen Court Freehold Limited | Real estate | 2016 |
| Bowerbeck Properties Limited | Administrative & support | 1983 |
| Bowes Capital Limited | Real estate | 2026 |
| Bowood 11 Limited | Professional & scientific | 2007 |
| Bowood Investments Limited | Real estate | 2021 |
| BP Exec Limited | Professional & scientific | 2014 |
| BP Strategic Management Ltd | Administrative & support | 2023 |
| BPM Hampton Ltd | Real estate | 2021 |
| BR Construction & Flooring Ltd | Construction | 2026 |
| Braaks Smiles Limited | Health & social care | 2022 |
| Bracknell Pizza Limited | Hospitality | 2024 |
| Bradley Aviation Limited | Professional & scientific | 2007 |
| Braexpert Holdings Limited | Extraterritorial | 2016 |
| Braexpert Limited | Professional & scientific | 2018 |
| Bragaglia Estates Limited | Construction | 2024 |
| Bragaglia Investments Ltd | Hospitality | 2016 |
| Brain Bloom Education Ltd | Education | 2025 |
| Brain Health Practice Limited | Professional & scientific | 2024 |
| Brainsells UK Limited | Construction | 1998 |
| Bramlore Limited | Professional & scientific | 2025 |
| Branching OUT Gardening Services Limited | Administrative & support | 2014 |
| Brand and Culture Videos Ltd | Information & communication | 2022 |
| Brand X Distribution Ltd | Wholesale & retail | 2005 |
| Brand YOU Designs Ltd | Professional & scientific | 2024 |
| Brandbabes Ltd | Professional & scientific | 2021 |
| Brandon Foran Ltd. | Real estate | 2022 |
| Brans Store Limited | Wholesale & retail | 2025 |
| Brants Property Company Limited | Extraterritorial | 1963 |
| Braveer Ltd | Professional & scientific | 2020 |
| Brawny Base Properties Ltd | Real estate | 2022 |
| Breakdown Ltd | Transport & logistics | 2020 |
| Brecon Freeholds Limited | Extraterritorial | 1962 |
| Breezion.Store Ltd | Manufacturing | 2026 |
| Brendan Construction Ltd | Construction | 2023 |
| Brent & Barnet Builders Limited | Construction | 2025 |
| Brent Nablus Twinning Association CIC | Education | 2025 |
| Brevevita Ltd | Other services | 2017 |
| Brevoro Ltd | Wholesale & retail | 2026 |
| Brick Projects (Chertsey) Limited | Real estate | 2012 |
| Brick Projects (Marland) Limited | Real estate | 2014 |
| Brick Projects (Queensgate) Limited | Real estate | 2013 |
| Brick Road Properties Ltd | Real estate | 2025 |
| Brickadoo Dover Limited | Real estate | 2026 |
| Bridge 2 Home Support Ltd | Hospitality | 2025 |
| Bridge Autos MK Ltd | Wholesale & retail | 2021 |
| Bridge Court (Harrow) RTM Company Limited | Households | 2022 |
| Bridge the GAP Safety Limited | Professional & scientific | 2022 |
| Bridgesky Ltd | Real estate | 2019 |
| Bridgewater JSK Ltd | Financial services | 2024 |
| Bridging the GAP Cild CIC | Other services | 2018 |
| Briela Building Services Design Limited | Professional & scientific | 2015 |
| Briggs Fiscal Limited | Financial services | 2004 |
| Bright Light Consultants Ltd | Wholesale & retail | 2022 |
| Bright Path Accountancy Services Ltd | Professional & scientific | 2026 |
| Bright Sky House Ltd | Real estate | 2016 |
| Bright Sparkle Cleaners Ltd | Administrative & support | 2024 |
| Bright View Property Estates Limited | Real estate | 2016 |
| Brighthaven Children's Services Ltd | Health & social care | 2026 |
| Brightraider Ltd | Administrative & support | 2013 |
| Brightspark Services Limited | Construction | 2008 |
| Brigo PT Ltd | Arts & recreation | 2015 |
| Bristlecone Pine Consultants Ltd | Professional & scientific | 2021 |
| Bristol Design UK Ltd | Wholesale & retail | 2023 |
| Bristol Edge Holding Limited | Real estate | 2026 |
| Bristol Edge Limited | Real estate | 2026 |
| Bristol Retail Limited | Administrative & support | 2014 |
| Britannia Accessories Limited | Wholesale & retail | 2024 |
| Britannia Biltong Ltd | Manufacturing | 2024 |
| Britannia Marketplace Ltd | Wholesale & retail | 2025 |
| Britannia Scaffolding Ltd | Construction | 2019 |
| British Friends of Yeshivat Eretz Hatzvi Limited | Education | 2009 |
| British Overseas & Export Trading Limited | Wholesale & retail | 1939 |
| Brix Care Ltd | Information & communication | 2021 |
| Brix Esolutions Ltd. | Information & communication | 2021 |
| Broadcast Fabrix Limited | Professional & scientific | 2015 |
| Broadfields Academy Trust | Education | 2013 |
| Broadgate International Limited | Financial services | 2005 |
| Broadhaven Construction Limited | Construction | 2009 |
| Broadwalk Food & Wine Ltd | Wholesale & retail | 2016 |
| Brock Management Ltd | Households | 2023 |
| Brookfields Health Care Ltd | Health & social care | 2022 |
| Brookside Residents Association (Old Stratford) Limited | Households | 1975 |
| Brothers JET Company Ltd | Wholesale & retail | 2021 |
| Browning Mews Limited | Real estate | 2013 |
| Broxi Limited | Wholesale & retail | 2026 |
| Bruce Barbers Limited | Administrative & support | 2017 |