| BKO Agency Ltd | Information & communication | 2026 |
| Black Belt Construction Limited | Construction | 2017 |
| Black Castle Scenery Limited | Construction | 2025 |
| Black Katz 2 Limited | Professional & scientific | 2015 |
| Black Katz Limited | Professional & scientific | 2024 |
| Black Label Hires Ltd | Transport & logistics | 2025 |
| Black Stone Mines Ltd | Mining & quarrying | 2025 |
| Blackthorn Procurement Limited | Other services | 2017 |
| Blaze Pizza Slough Ltd | Hospitality | 2021 |
| Blcksmth Apparel Ltd | Wholesale & retail | 2022 |
| Blessed Smile Ltd | Health & social care | 2022 |
| Blinksecure Limited | Other services | 2018 |
| Blooming Property Limited | Real estate | 2013 |
| Blue Elephant Interiors Ltd | Construction | 2022 |
| Blue Feather Designs Ltd | Professional & scientific | 2013 |
| Blue Moon Drinks Ltd | Wholesale & retail | 2025 |
| Blue Rose Shop Ltd | Wholesale & retail | 2018 |
| Blue Storm Group Limited | Wholesale & retail | 2021 |
| Blue UK Distribution Ltd | Wholesale & retail | 2022 |
| Blueberry Healthcare Limited | Administrative & support | 2021 |
| Blueberry Systems Limited | Information & communication | 2013 |
| Bluemoon Spice Ltd | Hospitality | 2025 |
| Bluerolls Bespoke Ltd | Wholesale & retail | 2024 |
| Blumen Capital Ltd | Professional & scientific | 2021 |
| BM Car Repairs Limited | Wholesale & retail | 2019 |
| BM Navigation Services Ltd | Transport & logistics | 2019 |
| BMB Plumbing & Heating Services Ltd | Construction | 2022 |
| BMC Building & Maintenance Ltd | Construction | 2026 |
| BMM Communications Ltd | Information & communication | 2026 |
| BN Insulation Services Ltd | Construction | 2016 |
| Boba Bliss Ltd | Hospitality | 2025 |
| Bodea Ltd | Construction | 2018 |
| Bodytech World Ltd | Wholesale & retail | 2022 |
| Bogmar Limited | Transport & logistics | 2021 |
| Boiler Services Lead Generation Ltd | Professional & scientific | 2019 |
| Boldbytes Ltd | Administrative & support | 2023 |
| Boleslaw Delikatesy Ltd | Wholesale & retail | 2013 |
| Boltrix Trading Limited | Wholesale & retail | 2025 |
| BOM Beef Ltd | Wholesale & retail | 2025 |
| Bombay Bicycle Club Ltd | Hospitality | 2025 |
| Bond Design and Build Limited | Construction | 2024 |
| Bonessi Ltd | Wholesale & retail | 2011 |
| Bonne Bouche Holdings Limited | Extraterritorial | 2026 |
| Bonvoyo Travels Ltd | Administrative & support | 2016 |
| Book Weaver Ltd. | Professional & scientific | 2017 |
| Bookselect-Uk Ltd | Education | 2012 |
| Boon London Limited | Construction | 2025 |
| Booze & Drinks Ltd | Wholesale & retail | 2021 |
| Booze Cruise Ltd | Wholesale & retail | 2015 |
| Borough Broth Company Limited | Manufacturing | 2015 |
| BOS Capital Property Group Ltd | Real estate | 2026 |
| Boscolo Tours UK Limited | Administrative & support | 2000 |
| Bosstech Electrical Ltd | Construction | 2017 |
| Boston Gilmore LLP | | 2006 |
| Bouncyzoo Ltd | Administrative & support | 2020 |
| Boundless 110 Limited | Information & communication | 2025 |
| Bowa Estates Ltd | Real estate | 2025 |
| Bowercroft Care Limited | Health & social care | 2014 |
| Boys Cafe Ltd | Hospitality | 2024 |
| BP Design & Build Ltd | Construction | 2025 |
| BPG 2006 Limited | Construction | 2015 |
| BPR Mortgage Planning Ltd | Financial services | 2021 |
| BR1 Automotive Limited | Wholesale & retail | 2026 |
| BR1 Chauffeurs Limited | Transport & logistics | 2024 |
| Braams Accountancy Limited | Professional & scientific | 2015 |
| Braams LLP | | 2008 |
| Bracknell Electrix Limited | Construction | 2015 |
| Bradfield Wholesale Ltd | Wholesale & retail | 2020 |
| Braerise (UK) Limited | Construction | 2012 |
| Brampton Educational Services Limited | Education | 1992 |
| Branch Logistics Ltd | Transport & logistics | 2025 |
| Breaker One Limited | Construction | 2025 |
| Breakfast Club Films Limited | Information & communication | 2011 |
| Breakhouse Hospitality Ltd | Hospitality | 2026 |
| Breakin' Form Limited | Information & communication | 2021 |
| BREAKINGBARRIERS2024 Ltd | Health & social care | 2023 |
| Breifne Properties Limited | Real estate | 2022 |
| Brendan D Property Limited | Real estate | 2012 |
| Brent United CIC | Education | 2023 |
| Brent United Football Club Limited | Education | 2023 |
| Brianks Limited | Hospitality | 2019 |
| Brickblue Fast Food Limited | Manufacturing | 2018 |
| Brickblue Homes Ltd | Real estate | 2022 |
| Brickblue Ltd | Construction | 1997 |
| Brickblue Medical Ltd | Information & communication | 2015 |
| Bright Car Motors Ltd | Wholesale & retail | 2024 |
| Bright Light OT Limited | Health & social care | 2024 |
| Brightside Haulage Ltd | Water & waste | 2020 |
| Brightwave Wholesale Ltd | Wholesale & retail | 2025 |
| Bril Look Ltd | Wholesale & retail | 2018 |
| Brim Burgers Edgware Road Ltd | Hospitality | 2025 |
| Brit Connect London Ltd | Administrative & support | 2026 |
| Brit Somali TV Ltd | Information & communication | 2021 |
| Britannia Building Construction and Services Ltd | Construction | 2014 |
| Britcart Enterprises Ltd | Wholesale & retail | 2024 |
| Britconnect International Ltd | Information & communication | 2023 |
| British Bangladesh Business Council Limited | Other services | 2015 |
| Brixell Construction Ltd | Construction | 2025 |
| Brizk Ltd | Other services | 1998 |
| Broad Catering Ltd | Hospitality | 2015 |