| Bruno Transport Limited | Transport & logistics | 2018 |
| Brunos London Ltd | Hospitality | 2025 |
| Brunswick Aces UK Ltd | Wholesale & retail | 2020 |
| Brunswick Cars Limited | Transport & logistics | 1997 |
| Brunswick Rose Limited | Hospitality | 2015 |
| Brush and Palette CIC | Arts & recreation | 2024 |
| Brutus Capital Co Ltd | Administrative & support | 2026 |
| Brvtglobal Ltd | Wholesale & retail | 2025 |
| Bryan Electrical Ltd | Construction | 2023 |
| Bryan Electrical Services Team Limited | Construction | 2017 |
| Bryan Gregory Lizzie Limited | Professional & scientific | 2024 |
| Bryant Court Management Limited | Real estate | 2004 |
| Bryant Davies Developments Ltd | Real estate | 2018 |
| Bryant Davies Investments Limited | Real estate | 2022 |
| Bryant Sound Ltd | Information & communication | 2023 |
| Bryce Building Solutions Ltd | Construction | 2021 |
| Brydon Electrical Limited | Energy | 2018 |
| Bryn Gilwern Energy Park Limited | Energy | 2020 |
| Bryn MOR Management Limited | Households | 1984 |
| Bryn Rhudd Energy Park Limited | Energy | 2021 |
| Bryn Spear Ltd | Wholesale & retail | 2026 |
| Bryn TEG Property RTM Company Limited | Real estate | 2014 |
| Bryn Wheeler Freelance Limited | Information & communication | 2020 |
| Bryn Y MOR Management Tenby 2015 Limited | Households | 2015 |
| Bryncroft Interiors Ltd | Wholesale & retail | 2025 |
| Brynderwen & Minster Medicals Limited | Health & social care | 2018 |
| Brynffynon Hotel Ltd | Hospitality | 2019 |
| Brynfield Court Owners Limited | Households | 1992 |
| Bryngwyn Energy Park Limited | Energy | 2021 |
| Brynithel Stores Ltd | Wholesale & retail | 2023 |
| Brynnsta Ltd | Real estate | 2021 |
| Brynteg Close Maintenance Limited | Real estate | 1973 |
| Brysen UK Ltd | Wholesale & retail | 2021 |
| Bryson Sales and Marketing Limited | Administrative & support | 2013 |
| Brythonic Information Technology (U.K.) Limited | Information & communication | 1985 |
| Bryvox Media Limited | Professional & scientific | 2025 |
| Bryzo Limited | Information & communication | 2025 |
| BRZ Property Limited | Real estate | 2020 |
| BS 1 Sauna Ltd | Financial services | 2015 |
| BS Computer & Telephones Ltd | Manufacturing | 2022 |
| BS Partnership Limited | Professional & scientific | 2012 |
| BS Parus Autocentre Ltd | Wholesale & retail | 2026 |
| BS Service Invest Limited | Extraterritorial | 2022 |
| BS1 Trading Limited | Hospitality | 2017 |
| Bsac Group Ltd | Information & communication | 2019 |
| BSB Floors & Walls Limited | Wholesale & retail | 2015 |
| BSC Shops (NO. 8) Limited | Transport & logistics | 1950 |
| Bscaor Poat Ltd | Wholesale & retail | 2025 |
| BSF Animal Nutrition Co., Ltd. | Extraterritorial | 2018 |
| BSG Capital Ltd | Financial services | 2026 |
| BSG Solutions Limited | Administrative & support | 2022 |
| Bsidescymru Ltd | Information & communication | 2018 |
| Bsmerchants Limited | Wholesale & retail | 2025 |
| BSO Services Limited | Transport & logistics | 2020 |
| BSP Autocentre Ltd | Wholesale & retail | 2016 |
| BSP Sales Centre Ltd | Wholesale & retail | 2014 |
| Bsrco Ltd | Wholesale & retail | 2025 |
| Bstar Tech Ltd | Other services | 2019 |
| BSV Entertainment Ltd | Hospitality | 2023 |
| BSV SEL PC | | 2020 |
| BSW Bathrooms Ltd | Construction | 2019 |
| BT Builders and Landscaping Ltd | Construction | 2021 |
| Bta.Fitness Ltd | Health & social care | 2019 |
| BTC Vault Ltd | Information & communication | 2026 |
| Btcle Ltd | Information & communication | 2024 |
| Btcmining Limited | Financial services | 2024 |
| Btekn Limited | Information & communication | 2001 |
| Btime Ltd | Professional & scientific | 2018 |
| BTL Marketing Group Limited | Professional & scientific | 2016 |
| BTL Online Ltd | Information & communication | 2025 |
| BTO Consulting Services Ltd | Wholesale & retail | 2019 |
| Btok Ltd | Information & communication | 2021 |
| BTP Northampton Limited | Construction | 2014 |
| BTS Building Contractors Limited | Construction | 2009 |
| Btsk Solutions PVT Ltd | Information & communication | 2026 |
| Btsl Tech Limited | Information & communication | 2018 |
| Btsm Verwaltungs Ltd | Administrative & support | 2017 |
| Btst France Limited | Administrative & support | 2008 |
| Btst Talex Ltd | Administrative & support | 2017 |
| BTT Group Finance Ltd | Professional & scientific | 2018 |
| BTT Ltd | Information & communication | 2024 |
| Btxnsl Mart Ltd | Wholesale & retail | 2025 |
| BU Agency Limited | Professional & scientific | 2024 |
| BU Group Limited | Professional & scientific | 2024 |
| BU Kebab Ltd | Hospitality | 2025 |
| BU Talent Limited | Professional & scientific | 2024 |
| Bu&Om Commerce Ltd | Wholesale & retail | 2025 |
| Buagile Ltd | Information & communication | 2025 |
| BUB1 Ltd | Professional & scientific | 2022 |
| Bubble Boba Cardiff Limited | Hospitality | 2017 |
| Bubble Car Wash Cardiff Ltd | Other services | 2025 |
| Bubble Health & Safety Limited | Professional & scientific | 2012 |
| Bubble Nation Ltd | Hospitality | 2021 |
| Bubblegum Overseas Limited | Wholesale & retail | 2025 |
| Bubblekaraoke Ltd | Hospitality | 2024 |
| Bubbles Asset Finance Limited | Financial services | 2021 |
| Bubbles&Cocktails Ltd | Hospitality | 2023 |
| Bubblevan Limited | Transport & logistics | 2018 |
| Bubbly Bandits Ltd | Wholesale & retail | 2021 |
| Bucci Properties Limited | Real estate | 2016 |