| Black and White Flooring Ltd | Wholesale & retail | 2022 |
| Black Brick Brothers Limited | Real estate | 2018 |
| Black Crow Logistics Ltd | Transport & logistics | 2019 |
| Black Diamond Estates Limited | Construction | 2025 |
| Black Essence London Ltd | Other services | 2021 |
| Black Girl Knit Club Ltd | Arts & recreation | 2020 |
| Black Horse Care Limited | Health & social care | 2022 |
| Black Lane Services Ltd | Other services | 2018 |
| Black Opall Ltd | Manufacturing | 2024 |
| Black Sand Trading Ltd | Professional & scientific | 2024 |
| Black Shield Protection Ltd | Financial services | 2025 |
| Black Vinyl Consulting Services Ltd | Professional & scientific | 2024 |
| Blackhorse Motors Ltd | Wholesale & retail | 2017 |
| Blaker Abbey Limited | Construction | 2023 |
| Blender Collective Ltd | Arts & recreation | 2024 |
| Blessed Adaeze Care Services Limited | Health & social care | 2018 |
| Blessed Assured Enterprise Limited | Health & social care | 2022 |
| Blessed Health Care Professionals UK Ltd | Health & social care | 2025 |
| Blinkscope Publishers Ltd | Information & communication | 2024 |
| Bliss Sports UK Ltd | Wholesale & retail | 2026 |
| Blissmax Ltd | Wholesale & retail | 2021 |
| Block Content Ltd | Information & communication | 2023 |
| Blog Autos Ltd | Wholesale & retail | 2021 |
| Blossoms Care Ltd | Health & social care | 2019 |
| BLU Diamond Services Limited | Administrative & support | 2013 |
| Blue Bay Investments Ltd | Real estate | 2004 |
| Blue Brooke Limited | Education | 2021 |
| Blue Catering London Limited | Hospitality | 2021 |
| Blue Diamond (UK) Ltd | Wholesale & retail | 2013 |
| Blue Diamonds Solutions Ltd | Real estate | 2021 |
| Blue Dream Academic Services Ltd | Education | 2021 |
| Blue Icon Trade Ltd | Manufacturing | 2023 |
| Blue Orchid Restaurant Ltd | Hospitality | 2025 |
| Blue Peak Recruitment Ltd | Administrative & support | 2026 |
| Blue Water Hub Ltd | Administrative & support | 2026 |
| Bluefox Books Limited | Professional & scientific | 2023 |
| Blueice Productions Ltd | Wholesale & retail | 2014 |
| Bluelights Properties Limited | Real estate | 2006 |
| Bluep Services Ltd | Health & social care | 2020 |
| BLW Secretariat Ltd | Administrative & support | 2018 |
| BMI Trades UK Ltd | Health & social care | 2017 |
| BML BS Itorizin Ltd | Information & communication | 2019 |
| BML World Ltd | Wholesale & retail | 2018 |
| Bmoneywize CIC | Education | 2010 |
| Bmvictory Ltd | Construction | 2019 |
| BN Furniture Ltd | Wholesale & retail | 2025 |
| BNB Holdings Ltd | Hospitality | 2026 |
| BNK Security Services Ltd | Administrative & support | 2024 |
| BNS Property Solutions Ltd | Real estate | 2025 |
| BO International UK London Ltd | Professional & scientific | 2017 |
| Boabab Solutions Ltd | Information & communication | 2017 |
| BOB Commerce Limited | Construction | 2018 |
| BOB Dawson Steam Plant Services Limited | Manufacturing | 2025 |
| Boba Garden Limited | Hospitality | 2020 |
| Bobak Services Limited | Public administration | 2020 |
| Bobble Homes Ltd | Construction | 2022 |
| Bobby's Fish Limited | Wholesale & retail | 2013 |
| Bobonsu Limited | Construction | 2025 |
| Bodysupply+ Ltd | Wholesale & retail | 2025 |
| Bodytouch UK Ltd | Wholesale & retail | 2017 |
| Bogdan&Anca Ltd | Construction | 2023 |
| BOILERS4U London Ltd | Construction | 2023 |
| Boji Construction Limited | Construction | 2017 |
| Bold Start Ltd | Wholesale & retail | 2025 |
| Boleyn Recovery & Fleet Services Limited | Manufacturing | 2002 |
| Boleyn Transport Holdings Limited | Manufacturing | 2018 |
| Bolta Services Limited | Professional & scientific | 2015 |
| Boltano Limited | Administrative & support | 2016 |
| Bombay Lanes Limited | Hospitality | 2025 |
| Bombshell Bakes Ltd | Hospitality | 2018 |
| BON Konprann Ltd | Information & communication | 2025 |
| Bona Management Ltd | Professional & scientific | 2019 |
| Bonab Kismet Ltd | Health & social care | 2023 |
| Bondad DE Dios Ltd | Real estate | 2021 |
| Bonitos Solutions Ltd | Information & communication | 2024 |
| Boniventure & SON Limited | Construction | 2026 |
| Bonum Dental Ltd | Health & social care | 2014 |
| Booth Brotherz Limited | Administrative & support | 2023 |
| Born 2 Travel Ltd | Information & communication | 2023 |
| Boshoe Ltd | Wholesale & retail | 2025 |
| Boski Limited | Wholesale & retail | 2006 |
| Bosscrowns Film and Drama School | Arts & recreation | 2015 |
| Boston Carparks Ltd | Real estate | 2025 |
| Boston Central Carpark Ltd | Real estate | 2025 |
| Boston Quilt Company Ltd | Wholesale & retail | 2022 |
| Boukketybeautyaffairs Ltd | Other services | 2025 |
| Boulevard Clothing Limited | Other services | 2014 |
| Bounds Green Pharmacy Limited | Wholesale & retail | 2026 |
| BOW Wharf Development LLP | | 2014 |
| BOZ & G Properties Limited | Real estate | 2024 |
| BOZ Supermarket Limited | Wholesale & retail | 2018 |
| BR Rail and Civils Ltd | Construction | 2024 |
| BR Traffic Management Ltd | Administrative & support | 2014 |
| Braided by Sade Limited | Other services | 2022 |
| Brain Technologies Ltd | Wholesale & retail | 2025 |
| Brainiac Solutions Limited | Administrative & support | 2013 |
| Brainybytes Ltd | Information & communication | 2025 |
| Brallo Limited | Professional & scientific | 2025 |
| Brand Caree Ltd | Wholesale & retail | 2024 |
| Branded Beauty Limited | Wholesale & retail | 2013 |