| Britannia Homes (Midlands) Ltd | Construction | 2018 |
| BRM Northants Limited | Construction | 2025 |
| Broad Green Solutions Limited | Administrative & support | 2014 |
| Broadhurst UK Limited | Real estate | 2004 |
| Broadway Kettering Ltd | Transport & logistics | 2025 |
| Broadway Stores Ltd | Wholesale & retail | 2014 |
| Brodier Investment Properties Ltd | Real estate | 2024 |
| Brompton 360 Homes Limited | Health & social care | 2024 |
| Brompton 360 Properties Limited | Real estate | 2019 |
| Brooke House Properties Limited | Construction | 2013 |
| Brookfield Wines Ltd | Agriculture & fishing | 2024 |
| Brooking Roofing Ltd | Construction | 2011 |
| Brooklands Accountants Ltd | Professional & scientific | 2017 |
| Brooklands Court (Kettering) Management Limited | Construction | 2007 |
| Brooklands Properties Limited | Real estate | 2023 |
| Brooklyn Bar Kettering Limited | Hospitality | 2018 |
| Brooksdale Properties Ltd | Real estate | 2023 |
| Brookson (5224P) Limited | Administrative & support | 2007 |
| Brotherhood Mens Groups CIC | Health & social care | 2025 |
| Broughton Airport & Contract Cars Limited | Transport & logistics | 2002 |
| Broughton Wines Limited | Wholesale & retail | 2005 |
| Browizorro Ltd | Other services | 2023 |
| Brown & Co. Consulting Ltd | Professional & scientific | 2025 |
| Brown & Mann Consultancy Limited | Professional & scientific | 2024 |
| Brownings Consultancy Ltd | Professional & scientific | 2025 |
| Browns Garage Limited | Wholesale & retail | 2023 |
| Browwow Beauty Ltd | Other services | 2021 |
| Broxwater Limited | Water & waste | 2017 |
| Brummie Holdings Ltd | Financial services | 2024 |
| Bruno's Care Limited | Health & social care | 2011 |
| Brutus Transport Services Limited | Transport & logistics | 2007 |
| Bryan and Boyt Ltd | Professional & scientific | 2003 |
| Brytech Ltd | Construction | 2013 |
| Brytr Properties Ltd | Construction | 2021 |
| BS Trade Ltd | Wholesale & retail | 2024 |
| BSK UK Trade Limited | Wholesale & retail | 2018 |
| Bsolve IT Limited | Information & communication | 2002 |
| BT Handbags & Gladrags Ltd | Wholesale & retail | 2015 |
| Btransport Ltd | Transport & logistics | 2025 |
| BTT Network Solutions Limited | Information & communication | 2007 |
| Bttlr Limited | Administrative & support | 2012 |
| Bubble Utilities Limited | Professional & scientific | 2018 |
| Buccleuch Holdings Limited | Professional & scientific | 2015 |
| Buccleuch Properties Limited | Professional & scientific | 2003 |
| Buccleuch Property (Basingstoke) Limited | Real estate | 2021 |
| Buccleuch Property (Beckton) Limited | Real estate | 2019 |
| Buccleuch Property (High Wycombe) Limited | Real estate | 2026 |
| Buccleuch Property (Kettering) Limited | Real estate | 2004 |
| Buccleuch Property (Scarborough) Limited | Real estate | 2019 |
| Buccleuch Property (Shawfair) Limited | Real estate | 2004 |
| Buccleuch Property (Towcester) Limited | Real estate | 2024 |
| Buccleuch Property (Tyne Tees) Limited | Real estate | 2005 |
| Buccleuch Property (Washington) Limited | Construction | 2018 |
| Buccleuch Property Investment Managers Limited | Real estate | 2004 |
| Buccleuch Recreational Enterprises Limited | Arts & recreation | 1976 |
| Buccleuch Woodlands (South) Limited | Agriculture & fishing | 2015 |
| Buckle and Hide UK Limited | Wholesale & retail | 2022 |
| Buckmaster Investments Limited | Financial services | 2021 |
| Bucks Transport Services Ltd | Transport & logistics | 2014 |
| Build Your Future Developments Ltd | Professional & scientific | 2023 |
| Building Products Next Day Limited | Extraterritorial | 2020 |
| Bujia Ltd | Transport & logistics | 2022 |
| Bulai Tran Ltd | Transport & logistics | 2023 |
| Bully Range Ltd | Administrative & support | 2020 |
| Bunica Construction Ltd | Construction | 2026 |
| Bunkers Hill Farm Ltd | Agriculture & fishing | 2020 |
| Bunyans Mead Ltd | Real estate | 2025 |
| Buona Vista Limited | Real estate | 2021 |
| Burbidge Electrical Limited | Construction | 2019 |
| Burfield Investments Limited | Financial services | 2017 |
| Burford Materials Ltd | Administrative & support | 2002 |
| Burgerbrew Ltd | Hospitality | 2024 |
| Burkesworks Limited | Construction | 2026 |
| Burley Terrace Limited | Households | 1992 |
| Burns Labs Ltd | Information & communication | 2026 |
| Burnt Lemon (Chefs) Ltd | Hospitality | 2019 |
| Burrows Family Investments Limited | Financial services | 2022 |
| Burtifer Transport Ltd | Transport & logistics | 2026 |
| Burton Barber Ltd | Other services | 2025 |
| Burton Chillies Ltd | Hospitality | 2025 |
| Burton Fish and Chips Ltd | Extraterritorial | 2015 |
| Burton Kebab Ltd | Hospitality | 2026 |
| Burton Latimer Car Care Ltd | Wholesale & retail | 2021 |
| Burton Latimer Estates Ltd | Agriculture & fishing | 1988 |
| Burton Support Services Limited | Health & social care | 2023 |
| Busby Solutions Limited | Administrative & support | 2018 |
| Bush & Company Rehabilitation Limited | Health & social care | 2010 |
| Business & Consumer Choices Telemarketing Limited | Information & communication | 2014 |
| Business Growth Midlands Limited | Professional & scientific | 2015 |
| Business Systems Partners Ltd | Professional & scientific | 2026 |
| Buster Solutions Ltd | Construction | 2025 |
| Buttercup Maternity Therapies and Clinic Limited | Health & social care | 2018 |
| Butterfly Effect Digital Sign Writers Ltd | Administrative & support | 2021 |
| Buyhikingboots.Co.Uk Limited | Wholesale & retail | 2018 |
| Buzau Food Ltd | Wholesale & retail | 2024 |
| Buzz Properties Limited | Real estate | 2016 |
| Buzzard Hill Limited | Administrative & support | 2010 |
| Byrn Bakery Ltd | Manufacturing | 2021 |
| Byteit Ltd | Information & communication | 2021 |
| C & C Farming Enterprises Ltd | Agriculture & fishing | 2024 |