| Best-Option Childcare Services Limited | Health & social care | 2026 |
| Beta Accounting Ltd | Professional & scientific | 2014 |
| Beta-Love Ltd | Professional & scientific | 2011 |
| Betsys Breaks Ltd | Administrative & support | 2024 |
| Beyond the Ward CIC | Education | 2026 |
| Bfav Ltd | Professional & scientific | 2024 |
| BGT Care Limited | Health & social care | 2019 |
| Big Chewy Limited | Professional & scientific | 2008 |
| Big G Logistics Ltd | Transport & logistics | 2016 |
| Big Silver Bross Limited | Hospitality | 2025 |
| Bikerni Limited | Hospitality | 2009 |
| Billy Seymour Limited | Arts & recreation | 2016 |
| Biomarsh Environmental Ltd | Water & waste | 1973 |
| Bionicbreakz Ltd | Information & communication | 2026 |
| Bircherley Developments Ltd | Construction | 2016 |
| Bits + Pieces Limited | Information & communication | 2011 |
| BK Interior & Exterior Ltd | Construction | 2023 |
| BK Plant Ltd | Construction | 2016 |
| Black Dove Capital Ltd | Professional & scientific | 2016 |
| Black Eagle Holdings Limited | Real estate | 2019 |
| Black Eagle Scaffolding Ltd | Construction | 2011 |
| Black Rock Construction and Rigging Limited | Information & communication | 2024 |
| Blackhorse Owners Management Limited | Real estate | 2003 |
| Blacksea Trade Ltd | Other services | 2024 |
| Blackthorne Specialist Joinery Ltd | Manufacturing | 2017 |
| Blade and Beauty Ltd | Other services | 2026 |
| Blasé Creative Ltd | Arts & recreation | 2018 |
| Blaze & Barrel Group Limited | Administrative & support | 2025 |
| Blaze & Barrel Limited | Wholesale & retail | 2025 |
| Blck Cat Social Ltd | Professional & scientific | 2026 |
| Blend & Bloom Cafe Ltd | Hospitality | 2026 |
| Blhack London Ltd | Wholesale & retail | 2023 |
| Blind Mice Productions Limited | Information & communication | 2016 |
| Block Management 24 Ltd | Real estate | 2017 |
| Blomfolk Ltd | Wholesale & retail | 2023 |
| Blood Cousins Group Ltd | Wholesale & retail | 2025 |
| Bloom & Colony Group Ltd | Real estate | 2023 |
| Bloomers Florist Cafe Limited | Hospitality | 2022 |
| Blossom Assessments Ltd | Health & social care | 2023 |
| Blowing Point Consultants Ltd | Professional & scientific | 2025 |
| Blowingpoint Enterprises Limited | Health & social care | 2013 |
| Blue ASS FLY Limited | Extraterritorial | 2015 |
| Blue Butterfly Gardens Ltd | Other services | 2019 |
| Blue Ice Holdings Limited | Real estate | 2018 |
| Blue Ice Machines Limited | Wholesale & retail | 2010 |
| Blue Orange Limited | Administrative & support | 2018 |
| Blue Pro Ltd | Financial services | 2022 |
| Bluebyte Ltd | Wholesale & retail | 2024 |
| BM London Luxe Builds Ltd | Construction | 2025 |
| BMA Property Solutions Ltd | Construction | 2022 |
| BNT Cars Limited | Wholesale & retail | 2021 |
| Bodybysim Limited | Arts & recreation | 2023 |
| Bogards Investments Limited | Real estate | 2019 |
| Bogards Property Management Limited | Real estate | 2019 |
| Boggatti Food Ltd | Wholesale & retail | 2021 |
| Boiler & Plant Dismantlers Limited | Construction | 2004 |
| Bolat Transport and Courier Ltd | Manufacturing | 2020 |
| Bond Garden Services Ltd | Administrative & support | 2025 |
| Boobas Fish Bar Limited | Hospitality | 2017 |
| Bool Properties Ltd | Real estate | 2025 |
| Boomerang IP Ltd | Extraterritorial | 2019 |
| Borboleta Media Limited | Information & communication | 2020 |
| Borley Brothers Holdings Limited | Financial services | 2020 |
| Bosphorus Barber & Barista Ltd | Other services | 2026 |
| Box Farm Ltd | Agriculture & fishing | 2025 |
| Boxdelux Ltd | Wholesale & retail | 2012 |
| Bpmg Construction Limited | Construction | 2026 |
| Bpmg Developments Limited | Construction | 2026 |
| Braddon Contracts Limited | Construction | 1994 |
| Brakkus Towers Ltd | Real estate | 2017 |
| Brandberry Consultancy Limited | Information & communication | 2021 |
| Brandex Global Ltd | Administrative & support | 2026 |
| Bray Family Homes Limited | Construction | 2017 |
| Brazilian Emporium Ltd | Wholesale & retail | 2020 |
| Breakfree Forever Consultancy Limited | Extraterritorial | 2018 |
| Brentwood Kebab Ltd | Hospitality | 2026 |
| Bricks and Mortar Assets Ltd. | Real estate | 2011 |
| Bridging Loans Essex Ltd | Professional & scientific | 2017 |
| Bridging Loans London Ltd | Professional & scientific | 2018 |
| Bright Integrated Solutions Ltd | Transport & logistics | 2022 |
| Britannia K9 Security Limited | Administrative & support | 2015 |
| Britcraft Timber Windows and Doors Ltd | Manufacturing | 2025 |
| Britexecstays Ltd | Hospitality | 2025 |
| Brits Transfers Ltd | Transport & logistics | 2023 |
| Brondesbury Park Limited | Real estate | 2024 |
| Brooker 113-117 Ltd | Real estate | 2026 |
| Brooker 180 Ltd | Real estate | 2026 |
| Brooklynrose Ltd | Wholesale & retail | 2020 |
| Brookmans Park Investments Limited | Real estate | 2017 |
| Brothers at Cobbs Limited | Hospitality | 2022 |
| Brown & Langley Limited | Real estate | 2024 |
| Broxbourne Interiors Limited | Construction | 2017 |
| BRS Cleaning Contractors Limited | Other services | 2013 |
| Brunello Group Ltd | Administrative & support | 2023 |
| BSM (Cleaning) Ltd | Administrative & support | 2025 |
| BSM Building Solutions and Maintenance Ltd | Construction | 2022 |
| BTP Construction Ltd | Construction | 2022 |
| Bubble Brothers Valets and Detailing Ltd | Administrative & support | 2020 |
| Bubble Duck Marketing Ltd | Professional & scientific | 2024 |
| Bubuteam Ltd | Wholesale & retail | 2024 |