| Bitran Group Limited | Administrative & support | 2012 |
| Bivq Ltd | Education | 2025 |
| Bizness Link Limited | Professional & scientific | 2010 |
| BJ Builders Ltd | Construction | 2019 |
| BJK Marketing Ltd | Wholesale & retail | 2021 |
| BJR Painting Services Ltd | Construction | 2026 |
| Bkamp Properties Ltd | Real estate | 2019 |
| BL Builders Limited | Construction | 2026 |
| BL Coins and Bullion Ltd | Manufacturing | 2025 |
| BL E-Commerce Ltd | Wholesale & retail | 2026 |
| Black Book Finance Ltd | Administrative & support | 2016 |
| Black HAT Productions Ltd | Information & communication | 2013 |
| Black Leaf-Uk Ltd | Construction | 2017 |
| Black to White Electrical Contractors Ltd | Construction | 2020 |
| Black Tulip (London) Limited | Administrative & support | 2002 |
| Blackbird Lands Ltd | Real estate | 2021 |
| Blackfields Legal Services Limited | Professional & scientific | 2017 |
| Blackheath Investments Ltd | Real estate | 2003 |
| Blacksheep Embroidery Limited | Manufacturing | 2005 |
| Blackspire Consulting Ltd | Information & communication | 2025 |
| Blade Sports Ltd | Wholesale & retail | 2012 |
| Blakeholt Ltd | Construction | 2013 |
| Blarney Stone Hotel Limited | Real estate | 2019 |
| Blarney's Limited | Hospitality | 2010 |
| Blascu Ltd | Transport & logistics | 2024 |
| BLC Carpentry Ltd | Manufacturing | 2026 |
| BLD Contractors Ltd | Construction | 2021 |
| Blenheim Commercial Limited | Real estate | 2005 |
| Blinds Empire Ltd | Wholesale & retail | 2018 |
| BLM Building Services Ltd | Construction | 2026 |
| BLM Pizza & Grill Limited | Hospitality | 2024 |
| Blockchain World Ltd | Information & communication | 2021 |
| Blockworm Limited | Professional & scientific | 2018 |
| Bloom Field International Trading Ltd | Wholesale & retail | 2018 |
| Bloomax Ltd | Education | 2016 |
| Bloomingdells Development Corporation Ltd | Professional & scientific | 2018 |
| Bloomsbury Big Top Limited | Arts & recreation | 2009 |
| Bloxhall Estates Limited | Real estate | 2020 |
| Bloxhall Estates SUB Ltd | Real estate | 2025 |
| BLU 2002 Limited | Wholesale & retail | 2001 |
| Blue Apple Trading Limited | Wholesale & retail | 2017 |
| Blue Autos Pro Ltd | Wholesale & retail | 2024 |
| Blue Balloon London Ltd | Wholesale & retail | 2024 |
| Blue Bay Home Care Ealing Limited | Health & social care | 2024 |
| Blue Bay Home Care Group Limited | Financial services | 2024 |
| Blue Bay Home Care Limited | Health & social care | 2015 |
| Blue Court Dental Centre Limited | Extraterritorial | 2010 |
| Blue Day Capital Ltd | Financial services | 2013 |
| Blue Delphi Ltd | Real estate | 2023 |
| Blue FIN Interiors Limited | Construction | 2005 |
| Blue Ginger Bar & Restaurant Limited | Hospitality | 2004 |
| Blue Launderette Services Ltd | Other services | 2011 |
| Blue Light Film & Presentation Services Ltd | Information & communication | 2009 |
| Blue Oak Partners Ltd | Wholesale & retail | 2025 |
| Blue Oasis Ltd | Real estate | 2013 |
| Blue Penguin Gifts Ltd | Wholesale & retail | 2024 |
| Blue Ribbon Music Limited | Information & communication | 1969 |
| Blue Rock Growth Ltd | Professional & scientific | 2025 |
| Blue Satellite Holdings Limited | Financial services | 2020 |
| Blue Skiesz Limited | Real estate | 2026 |
| Blue Snow Investments Limited | Financial services | 2021 |
| Blue Sustainable Power Ltd | Energy | 2025 |
| Bluelion Real Estate Limited | Real estate | 2017 |
| Bluenora Estates Limited | Real estate | 2026 |
| Bluerider Art UK Ltd | Wholesale & retail | 2022 |
| Bluesky Bliss Estates Ltd | Real estate | 2024 |
| Bluespoke Ltd | Information & communication | 2023 |
| Bluestorm Consulting (Evolution) Ltd | Administrative & support | 2024 |
| Bluestorm Consulting (London) Ltd | Professional & scientific | 2016 |
| Bluetickdata Ltd | Information & communication | 2025 |
| BM Centre Limited | Wholesale & retail | 2016 |
| Bmak Properties Ltd | Real estate | 2023 |
| BMD Entertainment Ltd | Information & communication | 2019 |
| BMD Plumbing & Heating Engineering Ltd | Construction | 2016 |
| Bmfr Ltd | Administrative & support | 2014 |
| BNH Infotech Ltd | Information & communication | 2024 |
| Boadicea the Victorious Ltd | Wholesale & retail | 2025 |
| BOB Drylining Ltd | Construction | 2018 |
| Bob's Your Uncle Research & Planning Limited | Information & communication | 2006 |
| Bobu Building Ltd | Manufacturing | 2024 |
| Bodefi Limited | Information & communication | 2015 |
| Bodilight Beauty Clinic Ltd | Wholesale & retail | 2003 |
| Bodilight Kent Limited | Wholesale & retail | 2016 |
| Body and Mind Connection Limited | Arts & recreation | 2025 |
| Body and Mind Healthcare Clinic Limited | Health & social care | 2023 |
| Body Ballancer Systems UK Ltd | Professional & scientific | 2017 |
| Body Essence Limited | Health & social care | 2004 |
| Bodyguard 24/7 Ltd | Administrative & support | 2025 |
| Bogota Estates Limited | Real estate | 2015 |
| Boicu Construction Ltd | Construction | 2026 |
| Boldenterprises Ltd | Wholesale & retail | 2025 |
| Bolenehair Ltd | Other services | 2026 |
| Bolterdal Ltd | Other services | 2026 |
| Bolton Design Services Limited | Professional & scientific | 2022 |
| Bolton Travel Ltd | Administrative & support | 2017 |
| Bomenda Limited | Professional & scientific | 2022 |
| BON Bonnie Properties Limited | Real estate | 2015 |
| Boniappetit Ltd | Information & communication | 2023 |
| Bonmere Limited | Professional & scientific | 2024 |
| Bonne Maison Properties Limited | Real estate | 2025 |