| Bruno(Men's Wear)Limited | Wholesale & retail | 1966 |
| BS Electrical Contractors Ltd | Construction | 2011 |
| BSB Construction Management Services Limited | Construction | 2016 |
| BSD Gifts Limited | Wholesale & retail | 2015 |
| Bsdyid Ltd | Wholesale & retail | 2024 |
| BSN UK Limited | Other services | 2023 |
| Bspoke Vacations Limited | Administrative & support | 2025 |
| BSR Media Limited | Information & communication | 2018 |
| BST Associates Limited | Professional & scientific | 2011 |
| Btechy Consultancy Services Ltd | Real estate | 2022 |
| BTL Network Ltd | Information & communication | 2017 |
| Buba UK Ltd | Hospitality | 2024 |
| Bubble Tea (Croydon) Limited | Hospitality | 2023 |
| Bubbles Corp Ltd | Hospitality | 2021 |
| Buchard Investments Limited | Real estate | 2024 |
| Buckettsland Ltd | Other services | 2023 |
| Buckingham Stores Limited | Wholesale & retail | 2018 |
| Buckingham Training Ltd | Administrative & support | 2026 |
| Buckwood Properties Limited | Real estate | 2016 |
| Bucky's Mini Mart Limited | Wholesale & retail | 2025 |
| Bucky's News Ltd | Wholesale & retail | 2024 |
| Bucovina Bakery Limited | Manufacturing | 2013 |
| Bucovina in UK Ltd | Wholesale & retail | 2011 |
| BUD Construction Ltd | Construction | 2024 |
| Budding Learners Holdco Limited | Financial services | 2024 |
| Bughutch Ltd | Information & communication | 2019 |
| Build Centre MK Limited | Construction | 2022 |
| BUILD2GROW Limited | Professional & scientific | 2023 |
| Building Alpha Ltd | Construction | 2018 |
| Building Creation Ltd | Construction | 2020 |
| Building Developers Limited | Construction | 2010 |
| Buildscape 313 Ltd | Construction | 2025 |
| Buildsierra Limited | Administrative & support | 2002 |
| Buildwell Developments Ltd | Construction | 2016 |
| Built Differently Ltd | Wholesale & retail | 2017 |
| Bukaf Services Limited | Health & social care | 2015 |
| Bukasa Properties Ltd | Real estate | 2025 |
| Bukene Holdings Limited | Real estate | 2020 |
| Bukhara Ltd | Hospitality | 2025 |
| Bukka Express Limited | Hospitality | 2018 |
| Bulford Limited | Professional & scientific | 2008 |
| Bulkbasket Traders Ltd | Wholesale & retail | 2025 |
| Bulsho Cargo Services Ltd | Transport & logistics | 2020 |
| Bulstrode PUB Limited | Hospitality | 2006 |
| Bulu Limited | Manufacturing | 2009 |
| Bunciu Machineries Ltd | Wholesale & retail | 2025 |
| Buoyd Technologies PVT Limited | Information & communication | 2018 |
| Burmanic Ltd | Information & communication | 2018 |
| Burn Proof Limited | Construction | 2023 |
| Burnell House RTM Company Limited | Households | 2023 |
| Burnley's Tree Services Ltd | Other services | 2021 |
| Burnley’S Tree Services Ltd T/A BTS Pest Services Ltd | Other services | 2026 |
| Burnt Oak & Watling Ltd | Wholesale & retail | 2025 |
| Burnt Oak (Barbers) Ltd | Other services | 2024 |
| Burnt Oak Broadway Edgware Management Limited | Households | 2014 |
| Burnt Oak Fish Market Ltd | Wholesale & retail | 2025 |
| Burnt Oak House Ltd | Wholesale & retail | 2026 |
| Burnt Oak Luggage & Electronics Limited | Wholesale & retail | 2024 |
| Burnt Oak Market Ltd | Wholesale & retail | 2014 |
| Burnt Oak Nepalese Community | Health & social care | 2024 |
| Burnt Oak Property Ltd | Real estate | 2026 |
| Burntoak Food and Wine Ltd | Wholesale & retail | 2023 |
| Burntoak Wines Limited | Wholesale & retail | 2019 |
| Burnwood Investments Limited | Real estate | 2019 |
| Bushey Authentic Pilates Limited | Arts & recreation | 2026 |
| Bushey Validation Consultant Limited | Information & communication | 2021 |
| Business Integration Systems Ltd | Information & communication | 2008 |
| Business Leadership Coaching Ltd | Administrative & support | 2014 |
| Business Sales Ltd | Wholesale & retail | 2003 |
| Business Tech Services Ltd | Information & communication | 2025 |
| Business Travel News Limited | Other services | 1993 |
| Business WIN Ltd | Professional & scientific | 2014 |
| Busy Boards 123 Limited | Manufacturing | 2020 |
| Busybeez Cafe Ltd | Hospitality | 2024 |
| Bute Construction Ltd | Construction | 2020 |
| Bute Properties Limited | Real estate | 2024 |
| Buttons Nanny Limited | Health & social care | 2015 |
| Buyers Guides Ltd | Information & communication | 2025 |
| Buyola Ltd | Wholesale & retail | 2019 |
| Buzea Cleaning Ltd | Administrative & support | 2026 |
| Buzz Spark Devices Ltd | Manufacturing | 2023 |
| BV Events Ltd | Arts & recreation | 2023 |
| BV Executive Ltd | Transport & logistics | 2023 |
| BVA Limited | Other services | 2014 |
| BVP Group Limited | Financial services | 2026 |
| BY Megan Thomas Ltd | Other services | 2024 |
| BYA Accessories Ltd | Wholesale & retail | 2021 |
| BYF Development Ltd | Construction | 2019 |
| BYF Investment Ltd | Real estate | 2020 |
| Bykarina Limited | Wholesale & retail | 2020 |
| Byron & Honister Limited | Real estate | 2022 |
| Byteo Ltd | Construction | 2017 |
| Bywood Construction Limited | Construction | 2002 |
| Bzfulham Ltd | Real estate | 2021 |
| BZY Holdings Limited | Financial services | 2022 |
| C & G Autos Limited | Wholesale & retail | 2020 |
| C & S Supplies Limited | Wholesale & retail | 2011 |
| C a Build & Design Limited | Administrative & support | 2011 |
| C a T a HI Tech Electricians Limited | Construction | 2025 |
| C Anderson Plumbing & Heating Ltd | Construction | 2021 |