| Blackstone Properties South Yorkshire Ltd | Real estate | 2025 |
| Blackstone Sovereign Partnerships Limited | Real estate | 2021 |
| Blackthorn Intermediaries Ltd | Financial services | 2014 |
| Bladelock Door Limited | Manufacturing | 2015 |
| Bladez Barber Salon Ltd | Other services | 2023 |
| Blair Orthopaedics Limited | Health & social care | 2021 |
| Blake Construction Materials Limited | Manufacturing | 2020 |
| Blake Property Management Limited | Households | 2004 |
| Blakeney Point Search & Selection Limited | Administrative & support | 2006 |
| Bland Services Ltd | Manufacturing | 2018 |
| Blansco Ltd | Construction | 2024 |
| Blaq Stone Properties Ltd | Real estate | 2020 |
| Blaqstone Healthcare Ltd | Health & social care | 2022 |
| Blaqstone Hub Ltd | Wholesale & retail | 2025 |
| Blaren Ltd | Transport & logistics | 2016 |
| Blastech (Midlands) Ltd | Construction | 2020 |
| Blastech Transport Ltd | Transport & logistics | 2022 |
| Blaxton Aggregates Limited | Mining & quarrying | 2017 |
| Blaxton Investments Ltd | Professional & scientific | 2017 |
| Blaze IP Limited | Wholesale & retail | 2008 |
| Blaze Takeaway Ltd | Hospitality | 2025 |
| Blendbyhan Ltd | Other services | 2023 |
| Bless Your Heart Studio Ltd | Other services | 2025 |
| Blessed 2 Bless Realty Ltd | Real estate | 2023 |
| Blikkendaal Ltd | Professional & scientific | 2023 |
| Blind Ideas Limited | Wholesale & retail | 2000 |
| Blinds KW Ltd | Construction | 2021 |
| Blindspol Ltd | Construction | 2022 |
| Blindtarn Limited | Real estate | 1961 |
| Bling Bling Boutique UK Ltd | Wholesale & retail | 2025 |
| Bliss Fast Food Ltd | Hospitality | 2025 |
| Blizard Physiotherapy and Running Clinic Limited | Health & social care | 2012 |
| Bllox Limited | Wholesale & retail | 2022 |
| BLN Solutions Ltd | Administrative & support | 2025 |
| Block 9 Bolwell Court Rentals Ltd | Real estate | 2021 |
| Block 9 Eden Grove Rentals Ltd | Real estate | 2023 |
| Block 9 Holdings Ltd | Financial services | 2021 |
| Block 9 Investments Ltd | Financial services | 2022 |
| Block 9 Plant Ltd | Administrative & support | 2021 |
| Blockchain Support Centre Ltd | Administrative & support | 2021 |
| Blocksave Ltd | Administrative & support | 2019 |
| Blonda Limited | Transport & logistics | 2018 |
| Bloom & Grey Limited | Other services | 2024 |
| Bloom Room Ltd | Wholesale & retail | 2023 |
| Blooming Dough Ltd | Hospitality | 2023 |
| Bloomin’ Good Gardens Ltd | Administrative & support | 2025 |
| Blossom Care Franchising Ltd | Professional & scientific | 2025 |
| Blossom Futures CIC | Education | 2025 |
| Blossom Grove Childcare Ltd | Health & social care | 2021 |
| Blossom Holding Group Ltd | Financial services | 2020 |
| Blossom Home Care Ltd | Other services | 2015 |
| Bloww Hair and Beauty Ltd | Other services | 2013 |
| Blucher Limited | Other services | 2006 |
| Blue Bond Limited | Other services | 2021 |
| Blue Bower Investments Limited | Real estate | 2023 |
| Blue Bower Property Management Limited | Real estate | 2003 |
| Blue Box Disposables GB Ltd | Wholesale & retail | 2015 |
| Blue Box Office Solutions Ltd | Administrative & support | 2017 |
| Blue Box Storage (Bentley) Ltd | Administrative & support | 2025 |
| Blue Box Storage (Doncaster) Ltd | Other services | 2013 |
| Blue Fire Systems Ltd | Construction | 2023 |
| Blue Grape Software Ltd | Information & communication | 2015 |
| Blue Hydraulics Limited | Manufacturing | 2016 |
| Blue Lagoon Housing Ltd | Real estate | 2022 |
| Blue Lantern Creative Ltd | Extraterritorial | 2026 |
| Blue Logistic Support Ltd | Transport & logistics | 2020 |
| Blue Marble Communications Limited | Professional & scientific | 2014 |
| Blue Marble Projects Limited | Construction | 2022 |
| Blue Nile Coffee Limited | Hospitality | 2022 |
| Blue Peak Engineering Ltd | Construction | 2026 |
| Blue Pool Computer Services Limited | Information & communication | 2002 |
| Blue Ridge Solutions Limited | Agriculture & fishing | 2016 |
| Blue River Developments Limited | Real estate | 2023 |
| Blue Sky Modular Limited | Administrative & support | 2018 |
| Blue Sky Publishing Ltd | Information & communication | 2023 |
| Blue Soft Limited | Information & communication | 2019 |
| Blue Square Property Maintenance Ltd | Construction | 2018 |
| Blueaura Holdings Limited | Real estate | 2026 |
| Bluebell Pictures Limited | Information & communication | 2023 |
| Blueberry Gate Enterprises Ltd | Extraterritorial | 2026 |
| Bluechip Trade Ltd | Wholesale & retail | 2024 |
| Bluecrown Services Ltd | Real estate | 2026 |
| Blueharbor Metrics Ltd | Extraterritorial | 2026 |
| Blueharbour Innovations Ltd | Extraterritorial | 2026 |
| Blueharbour Logistics Ltd | Extraterritorial | 2026 |
| Bluehaven Analytics Ltd | Extraterritorial | 2026 |
| Bluehaven Consulting Ltd | Extraterritorial | 2026 |
| Bluehaven Energy Ltd | Extraterritorial | 2026 |
| Blueline Auto Services Ltd | Wholesale & retail | 2026 |
| Blueline Prime Ltd | Construction | 2026 |
| Blueprint 4LIFE Ltd | Information & communication | 2023 |
| Blueprint Homes (North) Ltd | Construction | 2025 |
| Bluerock Developments Ltd | Real estate | 2022 |
| Bluerock Distribution Ltd | Wholesale & retail | 2025 |
| Bluesky Property Doncaster Ltd | Real estate | 2025 |
| Bluet Studio Ltd | Arts & recreation | 2019 |
| Bluewell Digital Limited | Information & communication | 2019 |
| Blumint Digital Limited | Information & communication | 2024 |
| Bluspace Limited | Professional & scientific | 2017 |
| Blyth Accounting Services Limited | Professional & scientific | 2004 |