| Blackfin Independent Wealth LLP | | 2024 |
| Blackfin Wealth Management Limited | Professional & scientific | 2018 |
| Blackline Haulage Ltd | Transport & logistics | 2025 |
| Blackneeyz Inc. Ltd | Information & communication | 2023 |
| Blackpearl Accounts Ltd | Professional & scientific | 2015 |
| Blackseed Remedies Ltd | Wholesale & retail | 2025 |
| Blacksmith Technologies Ltd | Wholesale & retail | 2023 |
| Blackstone Insurance Brokers Limited | Financial services | 2008 |
| Blackstone Property Advisors Ltd | Real estate | 2021 |
| Blackstone Shipping UK Ltd | Transport & logistics | 2021 |
| Blackwood Brand Consultancy Ltd | Professional & scientific | 2019 |
| Blackwood Corporate Holdings Limited | Real estate | 2026 |
| Blaise Architectural Limited | Professional & scientific | 2008 |
| Blake-Ezra Photography Ltd | Professional & scientific | 2011 |
| Blancus UK Ltd | Wholesale & retail | 2025 |
| Blastr Green Steel Holdings Limited | Financial services | 2025 |
| Blastr Green Steel Limited | Manufacturing | 2024 |
| Bleakleys Tile Studio Ltd | Wholesale & retail | 2023 |
| Blend Food Ltd | Hospitality | 2025 |
| Blendcrown Limited | Households | 2000 |
| Blenheim Realty (Bucks) Ltd | Construction | 2020 |
| Blenheim Realty (Northants) Ltd | Real estate | 2022 |
| Blenheim WD Investments Ltd | Real estate | 2024 |
| Blessdome Ltd | Wholesale & retail | 2020 |
| Blessings 7 Limited | Health & social care | 2024 |
| Blink Consulting Solutions Ltd | Information & communication | 2016 |
| Blissful Homes 28 Ltd | Real estate | 2024 |
| BLK Transport Ltd | Transport & logistics | 2025 |
| Blocked UP Ltd | Water & waste | 2026 |
| Blockhaus Industries Limited | Administrative & support | 2025 |
| Bloom Autism Centre Ltd | Health & social care | 2024 |
| Bloom Educational Psychology Ltd | Education | 2025 |
| Blooming & Bloom Ltd | Information & communication | 2023 |
| Bloomlogic Ltd. | Wholesale & retail | 2018 |
| Bloomoak Limited | Health & social care | 2025 |
| Bloomplot Limited | Extraterritorial | 2025 |
| Blossom Medical Signatory Limited | Professional & scientific | 2021 |
| BLOSSOM365 LP | | 2017 |
| Blouberg Accounting Ltd | Professional & scientific | 2020 |
| Blpr London Ltd. | Administrative & support | 2012 |
| Blue Beauty Productions Limited | Information & communication | 2021 |
| Blue Chip Consultancy Ltd | Information & communication | 2011 |
| Blue Chip Funding Limited | Extraterritorial | 2001 |
| Blue Circle Inc Limited | Transport & logistics | 2018 |
| Blue Consultancy Services Ltd | Administrative & support | 2018 |
| Blue Crane Care Limited | Administrative & support | 2022 |
| Blue Fish Properties Limited | Real estate | 2001 |
| Blue HAT Associates Limited | Professional & scientific | 2016 |
| Blue House Drainage Ltd | Construction | 2011 |
| Blue House Services Ltd | Construction | 2014 |
| Blue Knight Living Care Ltd | Health & social care | 2023 |
| Blue Ledger Ltd | Professional & scientific | 2025 |
| Blue Lion House Ltd | Professional & scientific | 2024 |
| Blue Manor Investments Limited | Construction | 2001 |
| Blue Mindset Investment Ltd | Real estate | 2021 |
| Blue Mindset Limited | Information & communication | 2014 |
| Blue Mingo Marketing Limited | Professional & scientific | 2019 |
| Blue Monkey Technology Ltd | Information & communication | 2013 |
| Blue Moon Studios Ltd | Information & communication | 2025 |
| Blue Moth Consulting Limited | Administrative & support | 2024 |
| Blue Mountain Building Services Limited | Professional & scientific | 2023 |
| Blue Rock Developers Ltd | Construction | 2025 |
| Blue Skies Consultancy Ltd | Professional & scientific | 2025 |
| Blue Sky Corporation Limited | Wholesale & retail | 2018 |
| Blue Sky Funding Ltd | Professional & scientific | 2015 |
| Blue Sky Property Consultants Ltd | Construction | 2014 |
| Blue Sole Limited | Wholesale & retail | 2017 |
| Blue Spark Consultants Limited | Extraterritorial | 2021 |
| Blue Spark Organisation Limited | Administrative & support | 2005 |
| Blue Spark Recruitment Limited | Extraterritorial | 2021 |
| Blue Stone Engineering Solutions Ltd | Administrative & support | 2016 |
| Blue Tides Ltd | Information & communication | 2015 |
| Blue Trade Limited | Information & communication | 2023 |
| Blue Wave Ventures Ltd | Professional & scientific | 2024 |
| Blue Welcome Limited | Real estate | 2024 |
| Blueanimal Consulting Ltd | Information & communication | 2015 |
| Bluebell Homes (Herts) Limited | Real estate | 2017 |
| Bluebell PRE School a Community Interest Company | Health & social care | 2022 |
| Bluebelle SY Consultancy Ltd | Professional & scientific | 2014 |
| Bluebinary Limited | Information & communication | 2011 |
| Bluebrick Holdings Limited | Real estate | 2025 |
| Blueeye Drivers Ltd | Transport & logistics | 2015 |
| Bluefizz Ltd | Administrative & support | 2019 |
| Blueglass Consulting Limited | Administrative & support | 2016 |
| Bluejohn Ltd | Wholesale & retail | 2023 |
| Bluekart Ltd | Wholesale & retail | 2025 |
| Bluelake Energy Consultancy Limited | Other services | 2025 |
| Bluelodge Estates Limited | Construction | 1999 |
| Bluemars Transport Ltd | Transport & logistics | 2023 |
| Bluemoon Properties Limited | Real estate | 1998 |
| Bluepeak Design & Build Ltd | Construction | 2025 |
| Blueprint Entertainment Limited | Transport & logistics | 2000 |
| Blueprint Financial Consulting Ltd | Professional & scientific | 2017 |
| Blueridge Ventures Ltd | Information & communication | 2025 |
| Blues Analytics Limited | Information & communication | 2017 |
| Bluesteel Webdesign Limited | Information & communication | 2013 |
| Bluesting Ltd | Information & communication | 2020 |
| Bluestone Property Consultants Ltd | Real estate | 2016 |
| Bluet Consulting Limited | Administrative & support | 2024 |
| Bluetime Consulting Ltd | Information & communication | 2012 |