| Blocks 4 Hire Ltd | Administrative & support | 2009 |
| Blood Sausage Limited | Hospitality | 2026 |
| Bloomsbury Clinical Research Ltd | Professional & scientific | 2017 |
| Blubrite Ltd | Real estate | 2018 |
| Blue & Green Oval Services Limited | Transport & logistics | 2003 |
| Blue Boar Investment Holdings Ltd | Construction | 2023 |
| Blue Boar Properties Ltd | Construction | 2021 |
| Blue Box Property Maintenance Ltd | Other services | 2015 |
| Blue FOX Digital Ltd | Professional & scientific | 2024 |
| Blue Steel Property Limited | Real estate | 2023 |
| Blueagle Limited | Wholesale & retail | 2025 |
| Bluecat Consultancy Limited | Information & communication | 2017 |
| Bluefield Global Ltd | Wholesale & retail | 2026 |
| Bluegreen Holdings Ltd | Financial services | 2022 |
| Bluesky Asbestos Control Limited | Health & social care | 2017 |
| Bluewater Marketing Limited | Administrative & support | 2003 |
| Bluewing Digital Ltd | Information & communication | 2019 |
| Boards of Kettering CIC | Wholesale & retail | 2024 |
| Boddington Property Management Ltd | Households | 2023 |
| Bodenham Consulting Limited | Professional & scientific | 2026 |
| Bodily Landscapes Limited | Administrative & support | 2005 |
| Bodrum Turkish BBQ Ltd | Hospitality | 2025 |
| Body Perfections (Northants) Limited | Other services | 2016 |
| Body Poppers Limited | Wholesale & retail | 2010 |
| Bojar International Transport Ltd | Transport & logistics | 2018 |
| Boltholes Property Limited | Real estate | 2022 |
| Bomm Blinds Ltd | Other services | 2023 |
| Bonchurch Village Apartments Ltd | Real estate | 2022 |
| Bone Crypt Spirits Ltd | Manufacturing | 2023 |
| Bonham Court (Management) 2005 Ltd | Households | 2005 |
| Bonnieres Limited | Administrative & support | 2025 |
| Boob OR Bust Ltd | Wholesale & retail | 2016 |
| Book VIA US Ltd | Administrative & support | 2023 |
| Books Balanced Limited | Administrative & support | 2015 |
| Boom KEG Gaming Ltd | Wholesale & retail | 2019 |
| Boom Photography Ltd | Professional & scientific | 2024 |
| Booni Chat Ltd | Information & communication | 2025 |
| Boost Financial Services Limited | Financial services | 2021 |
| Booths Electrical Services Limited | Construction | 2017 |
| Border-Clash Restaurant and Bar Limited | Hospitality | 2024 |
| BOS Block Limited | Wholesale & retail | 2023 |
| Boss Burger Ltd | Hospitality | 2024 |
| Boston Diner Ltd | Hospitality | 2017 |
| Bosworth Gardens Management Company Limited | Real estate | 2007 |
| Bouchard & Bouchard (Properties) Limited | Construction | 2019 |
| Bouchard & Sons Limited | Real estate | 2022 |
| Boudoir Erotique Ltd | Wholesale & retail | 2024 |
| Boudouko Consulting Limited | Administrative & support | 2020 |
| Boughton Estates Limited(The) | Real estate | 1932 |
| Boughton Farming Limited | Agriculture & fishing | 2015 |
| Boughton Loam & Turf Management Limited | Extraterritorial | 1973 |
| Boughton Loam Limited | Manufacturing | 1969 |
| Boulevard Construction Services Limited | Construction | 2020 |
| Bouma Engineering Ltd | Professional & scientific | 2025 |
| Bourne Capability Development Ltd | Administrative & support | 2026 |
| Bourne Carpets & Floors Limited | Wholesale & retail | 2021 |
| Bowhill Development Company Limited | Construction | 1955 |
| Bowling Vision Limited | Wholesale & retail | 2006 |
| Bowyers Barber Shop Ltd | Other services | 2023 |
| Box Business Ltd | Administrative & support | 2022 |
| Boxwood Gardens Limited | Administrative & support | 2013 |
| Boxx Industries Limited | Financial services | 2022 |
| Boyle's Landscape Services Limited | Arts & recreation | 2010 |
| BP Grill Limited | Hospitality | 2025 |
| BPS Project Services Limited | Construction | 2016 |
| Braces News Ltd | Wholesale & retail | 2024 |
| Bradgate In-Situ Testing Limited | Construction | 2014 |
| Bradley Parr Building & Tiling Ltd | Construction | 2022 |
| Braich Investments Limited | Real estate | 2014 |
| Braines & Cope Limited | Professional & scientific | 2014 |
| Brambleside Academy Trust | Education | 2014 |
| Brambleside Roofing Limited | Construction | 2016 |
| Brar Property Investment Ltd | Real estate | 2025 |
| Brass Line Solutions Limited | Wholesale & retail | 2025 |
| Bravich Ltd | Wholesale & retail | 2016 |
| Bravo 9TH Limited | Hospitality | 2021 |
| Brazilian Flavor MK Ltd | Hospitality | 2024 |
| Brea Estimating Services Limited | Construction | 2016 |
| Breadline | Health & social care | 1997 |
| Breeze Ventilation Limited | Construction | 2024 |
| Brennan Bespoke Lettings Ltd | Real estate | 2025 |
| Brennan Bespoke Limited | Real estate | 2022 |
| BRH Bedroom Installations Limited | Construction | 2003 |
| Brian Martin Property Ltd | Real estate | 2023 |
| Bric Properties Limited | Real estate | 2002 |
| Brickworx and Developments Limited | Construction | 2021 |
| Bridge House (Newquay) RTM Company Limited | Households | 2023 |
| Bridges Engineering Limited | Professional & scientific | 2016 |
| Bridgewood Recycling Ltd | Water & waste | 2024 |
| Bridgman Precision Engineering Limited | Manufacturing | 2008 |
| Bright Data Ltd | Professional & scientific | 2024 |
| Bright Light Data Ltd | Information & communication | 2025 |
| Bright Spark Consultancy Limited | Financial services | 2019 |
| Brightening the Future of Stem Ltd | Education | 2023 |
| Brighter Financial Solutions Ltd | Professional & scientific | 2024 |
| Brighton Guni Group Ltd | Wholesale & retail | 2025 |
| Brigstock Boarding Kennels Ltd | Other services | 2014 |
| Brigstock Secure Services Ltd | Construction | 2020 |
| Brimarg Limited | Information & communication | 2024 |
| Britannia Estates & Developments Ltd | Real estate | 2025 |