| Bhava Holding Ltd | Financial services | 2023 |
| Bhava London Ltd | Real estate | 2023 |
| BIA Folláin Limited | Wholesale & retail | 2024 |
| Biamp Systems UK Ltd | Professional & scientific | 2011 |
| Bianca Group Ltd | Administrative & support | 2021 |
| Bici Construction Group Ltd | Other services | 2022 |
| Bici Contractors Ltd | Construction | 2022 |
| Big Bites Pizza & Burger Ltd | Hospitality | 2020 |
| Big Byte Media Limited | Information & communication | 2013 |
| Big Family Daycare Ltd | Health & social care | 2022 |
| Big REP Group Limited | Information & communication | 2026 |
| Biggerstage (UK) Limited | Information & communication | 2022 |
| Bigmo Solutions Ltd | Professional & scientific | 2026 |
| Billowes Consultancy Ltd | Information & communication | 2011 |
| Bina Manage Ltd | Real estate | 2024 |
| Binexa Ltd | Wholesale & retail | 2025 |
| Bingo’S Kitchen Ltd | Manufacturing | 2025 |
| Binns Bird Limited | Professional & scientific | 2016 |
| Biodplas Ltd | Administrative & support | 2020 |
| Biolizard Limited | Information & communication | 2020 |
| Biome Lube Ltd | Manufacturing | 2025 |
| Biopharma CMC Regulatory Consultancy Services Limited | Professional & scientific | 2016 |
| Birch & Sons Antiques Limited | Wholesale & retail | 2013 |
| Bird Build Limited | Construction | 1997 |
| Biscayne Solutions Ltd | Administrative & support | 2013 |
| Biscuit Bakery Ltd | Administrative & support | 2019 |
| Bite IT Marketing Limited | Professional & scientific | 2017 |
| Bizblast Limited | Wholesale & retail | 2025 |
| Bizpoak Ltd | Information & communication | 2024 |
| BK Property Investing Limited | Real estate | 2026 |
| BL Construction Services Ltd | Construction | 2016 |
| Black and White Marketing Limited | Professional & scientific | 2012 |
| Black Cat Broadcast Ltd | Information & communication | 2022 |
| Black Horse Construction and Engineering Ltd | Construction | 2026 |
| Black Horse Kingston Limited | Hospitality | 2025 |
| Black Lion Partnership Ltd | Real estate | 2019 |
| Black Square Mode Ltd | Other services | 2016 |
| Black Swan Currency Ltd | Financial services | 2020 |
| Black Water Tattoo Ltd | Other services | 2019 |
| Black White Music Limited | Information & communication | 2021 |
| Blackburn House LLP | | 2025 |
| Blacksheep Technologies Limited | Construction | 2025 |
| Blah Blah Blah Scripts Ltd | Arts & recreation | 2019 |
| Blayney Financial Limited | Extraterritorial | 2017 |
| Blayney Personnel Limited | Administrative & support | 2003 |
| Blazing Red Limited | Professional & scientific | 2024 |
| Bleep 360 Limited | Administrative & support | 2013 |
| Blendcourt Limited | Construction | 1992 |
| Blindspot Creative Ltd | Professional & scientific | 2016 |
| Blinkuk Eyecare Limited | Health & social care | 2008 |
| Bliss Teddington Ltd | Hospitality | 2021 |
| Blixem Ltd | Professional & scientific | 2022 |
| Blludog Limited | Wholesale & retail | 2023 |
| Blockfirmation Ltd | Information & communication | 2023 |
| Blok CMY Ltd | Wholesale & retail | 2023 |
| Blokheads Ltd | Professional & scientific | 2023 |
| Bloq.It Limited | Information & communication | 2025 |
| Blossom 360 Wealth Ltd | Professional & scientific | 2026 |
| Blossom Investments Holding Ltd | Financial services | 2025 |
| Blossom Maintenance Ltd | Households | 2023 |
| Blossom Ventures Limited | Financial services | 2009 |
| BLR Test Consultancy Limited | Information & communication | 2017 |
| BLU Construction Ltd | Construction | 2025 |
| Blue Avocado IT Ltd | Information & communication | 2011 |
| Blue Bridge Films Ltd | Professional & scientific | 2022 |
| Blue FIN Investor (UK) LLP | | 2018 |
| Blue GEM Catering Limited | Hospitality | 2015 |
| Blue Lagoon Travel Limited | Administrative & support | 2016 |
| Blue Medic Consultancy Limited | Health & social care | 2017 |
| Blue Oak Ltd | Real estate | 2022 |
| Blue Palette Art Studio Limited | Arts & recreation | 2017 |
| Blue River 01 Limited | Real estate | 2021 |
| Blue Seahorse Limited | Information & communication | 2021 |
| Blue Ship Corporation Limited | Financial services | 1985 |
| Blue Sky Thoughts Limited | Information & communication | 2013 |
| Blue Star Media Limited | Information & communication | 2020 |
| Blue Whale Technologies Co. Ltd | Manufacturing | 2019 |
| Blue ZOO Consulting & Coaching Ltd | Other services | 2012 |
| Bluechase 1 Limited | Other services | 2018 |
| Bluegrey Design Limited | Arts & recreation | 2020 |
| Bluelight Healthcare Group Limited | Administrative & support | 2015 |
| Bluepath Trading Ltd | Wholesale & retail | 2026 |
| Bluepin Management Limited | Administrative & support | 2011 |
| Blueprint CTO Ltd | Information & communication | 2019 |
| Bluesky Realty Investments Limited | Real estate | 2023 |
| Bluetechs UK Groups Limited | Mining & quarrying | 2013 |
| BMS Plastering and Alterations Limited | Construction | 2017 |
| BOA 1NVESTMENT Ltd | Financial services | 2019 |
| Board Game DEN Ltd | Wholesale & retail | 2021 |
| BOB Wheller Design Ltd | Professional & scientific | 2026 |
| Bobos Cleaning Company Ltd | Administrative & support | 2019 |
| Body and Brows Education Ltd | Education | 2020 |
| Body and Brows Ltd | Other services | 2014 |
| Boga Consulting Ltd | Information & communication | 2022 |
| Boga Films Ltd | Information & communication | 2020 |
| Bold Strokes Ltd | Professional & scientific | 2021 |
| Boldon Siding Consulting Ltd | Professional & scientific | 2024 |
| Bolger Limited | Professional & scientific | 2007 |
| Bompas Road Investments Limited | Professional & scientific | 2022 |
| Bonbon Pottery K Ltd | Wholesale & retail | 2025 |