| Blackburn & Price Ltd | Real estate | 2020 |
| Blackburn Road News Ltd | Wholesale & retail | 2019 |
| Blackburn Ymca | Other services | 2004 |
| Blackcrown Investments Limited | Financial services | 2026 |
| Blackedge Brewing Company Ltd | Manufacturing | 2009 |
| Blackedge Cask & Craft Ltd | Hospitality | 2019 |
| Blackedge Hospitality Limited | Hospitality | 2014 |
| Blackfield Landscapes Ltd | Administrative & support | 2024 |
| Blackflint Ltd | Professional & scientific | 2021 |
| Blackgold Metals Ltd | Wholesale & retail | 2020 |
| Blackgrid Cyber Limited | Information & communication | 2025 |
| Blackgrid Holdings Limited | Financial services | 2025 |
| Blackhorse Mews Management Company Limited | Households | 2018 |
| Blacklands Developments Ltd | Construction | 2023 |
| Blackout Watches UK Ltd | Wholesale & retail | 2026 |
| Blackresin Limited | Wholesale & retail | 2018 |
| Blackrod Consulting Limited | Information & communication | 2024 |
| Blackrod Electrical Solutions Ltd | Construction | 2026 |
| Blackrod House Limited | Health & social care | 2015 |
| Blackrod MOT Station Limited | Wholesale & retail | 2016 |
| Blackrod PUB Co Ltd | Hospitality | 2026 |
| Blackseedbaraka Ltd | Wholesale & retail | 2025 |
| Blackshaw Developments Limited | Real estate | 2004 |
| Blackstone (SH) Ltd | Extraterritorial | 2025 |
| Blackstone ARA Ltd | Real estate | 2024 |
| Blackstone Cloud Ltd | Information & communication | 2023 |
| Blackstone Investment Group Ltd | Real estate | 2018 |
| Blackstone Lettings Ltd | Real estate | 2012 |
| Blackstone Meats Ltd | Wholesale & retail | 2025 |
| Blackstone MSA Ltd | Real estate | 2024 |
| Blackthorn Leisure Ltd | Hospitality | 2017 |
| Blacktide International Ltd | Professional & scientific | 2025 |
| Blackun Ltd | Administrative & support | 2001 |
| Blackwave Tyres Ltd | Wholesale & retail | 2020 |
| Blackwood Accounting Solutions Ltd | Professional & scientific | 2015 |
| Blade Entertainment Limited | Information & communication | 2010 |
| Blade Pro Coaching Limited | Health & social care | 2025 |
| Blainscough Projects Ltd | Real estate | 2019 |
| Blake Laurence Limited | Other services | 2017 |
| Blank Canvas & Companies Ltd | Real estate | 2024 |
| Blank Canvas Design Studio Ltd | Professional & scientific | 2024 |
| Blank Canvas Learning Limited | Education | 2012 |
| Blank Canvas Property Ltd | Real estate | 2024 |
| Blank Screen Ltd | Hospitality | 2025 |
| Blazing Ahead Ltd | Information & communication | 2025 |
| Blazing Limited | Manufacturing | 2019 |
| Blazingly Fast Ltd | Information & communication | 2024 |
| Bleachworks Bike Shed Ltd | Wholesale & retail | 2021 |
| Blease Engineering Limited | Administrative & support | 2005 |
| Bleeper Services Limited | Manufacturing | 2001 |
| Bleeps Consulting Limited | Professional & scientific | 2023 |
| Blend Studio Creative Ltd | Professional & scientific | 2023 |
| Blenheim Schools Group Limited | Financial services | 2024 |
| Blenheim Schools Limited | Education | 2022 |
| Blessed Territory Ltd | Real estate | 2016 |
| Blessing Musabayana Services Ltd | Transport & logistics | 2025 |
| Blessyb Ltd | Wholesale & retail | 2021 |
| BLH Cleaning Limited | Administrative & support | 2025 |
| BLI & Maily Ltd | Other services | 2025 |
| Blick Locums Ltd | Professional & scientific | 2014 |
| Blindtex Ltd | Wholesale & retail | 2024 |
| Bling Nails & Spa Beauty Limited | Other services | 2024 |
| Blip Intelligence Ltd | Information & communication | 2025 |
| Bliss Aesthetics Supplies Ltd | Wholesale & retail | 2025 |
| Bliss Bridal (Bolton) Ltd | Wholesale & retail | 2021 |
| Bliss Life UK Ltd | Wholesale & retail | 2023 |
| Blitzy Occasion Ltd | Other services | 2024 |
| BLK Investment 2025 Ltd | Wholesale & retail | 2025 |
| Bloc Contracting Limited | Construction | 2026 |
| Block 4 Chester Ltd | Real estate | 2020 |
| Block Paving Limited | Construction | 2025 |
| Block Paving Specialist Ltd | Construction | 2026 |
| Blok Group Holdings Ltd | Wholesale & retail | 2026 |
| Blond Design Ltd | Extraterritorial | 2011 |
| Bloom & Wonder Limited | Wholesale & retail | 2025 |
| Bloom Architects Limited | Professional & scientific | 2016 |
| Bloom Street Hotel Limited | Construction | 2025 |
| Bloom Tools Limited | Wholesale & retail | 2025 |
| Bloomfed Limited | Wholesale & retail | 2015 |
| Bloomfield (Markland Hill) Management Company Limited | Real estate | 2007 |
| Blooming Brain Clinical Health Therapies Limited | Health & social care | 2026 |
| Blooming IT Limited | Administrative & support | 2014 |
| Bloot Holdings Ltd | Administrative & support | 2023 |
| Bloot Properties Ltd | Real estate | 2024 |
| Blossom Wealth Management Ltd | Financial services | 2018 |
| Blowers Atelier Ltd | Professional & scientific | 2025 |
| Blown Aesthetics Limited | Other services | 2024 |
| BLP Construction Limited | Construction | 2017 |
| BLP Design and Build Ltd | Construction | 2024 |
| Blpa Solutions Limited | Transport & logistics | 2025 |
| Bltn Group Limited | Professional & scientific | 2024 |
| BLU Sky Properties Ltd | Real estate | 2020 |
| Blue Capital Limited | Financial services | 2012 |
| Blue Construction Services Limited | Construction | 2012 |
| Blue Corpuscle Limited | Health & social care | 2019 |
| Blue Cross Helpline Ltd | Financial services | 2019 |
| Blue Diamond Riley Services Limited | Wholesale & retail | 2015 |
| Blue Ember Ltd | Wholesale & retail | 2025 |
| Blue Estates (NW) Ltd | Real estate | 2025 |
| Blue Horizon Capital Investments Ltd | Real estate | 2026 |