| Black Horse House Ltd | Real estate | 2015 |
| Black Horse Racing Ltd | Wholesale & retail | 2026 |
| Black IVY Ltd | Other services | 2010 |
| Black Label Prestige Ltd | Wholesale & retail | 2026 |
| Black Leaf Ltd | Wholesale & retail | 2026 |
| Black Moon Lounge Limited | Hospitality | 2021 |
| Black Moon Restaurant Ltd | Hospitality | 2025 |
| Black Oak Management Services Ltd | Households | 2025 |
| Black Olive Properties Limited | Real estate | 2018 |
| Black Olive Services Limited | Construction | 2020 |
| Black Quoin Ltd | Professional & scientific | 2025 |
| Black Robinia Constructions Ltd | Construction | 2025 |
| Black Seed Investments Limited | Real estate | 2005 |
| Black Uniform Ltd | Administrative & support | 2025 |
| Black Wolf Security Ltd | Administrative & support | 2017 |
| Black Woman Kindness CIC | Education | 2022 |
| Blackbook Music Limited | Information & communication | 2009 |
| Blackhorse Security Services Ltd | Administrative & support | 2025 |
| Blacknificent Ltd | Manufacturing | 2019 |
| Blackpool Prime Ltd | Real estate | 2020 |
| Blackridge Security Ltd | Administrative & support | 2026 |
| Blackrock Recruitment Services Limited | Professional & scientific | 2023 |
| Blackrock Restaurant Ltd | Hospitality | 2017 |
| BLACKST1 Media Ltd | Information & communication | 2017 |
| Blackstar Health & Material Science Ltd | Health & social care | 2009 |
| Blackstone Educational Services Ltd | Education | 2023 |
| Blackstone Group Security Ltd | Administrative & support | 2014 |
| Blackstone Landmarks Ltd | Real estate | 2022 |
| Blackstone Mortgage and Protection Ltd | Financial services | 2021 |
| Blackstone Trade Ltd | Administrative & support | 2025 |
| Blackthorn Legal Associates Limited | Other services | 2025 |
| Blackwood Residences Ltd | Real estate | 2023 |
| Blackzeroo Ltd | Information & communication | 2023 |
| Blacq Ltd | Professional & scientific | 2025 |
| Blakes TKS Ltd | Arts & recreation | 2019 |
| Blanariu Solutions Limited | Transport & logistics | 2022 |
| Blanche London Ltd | Other services | 2016 |
| Blank Stitch Ltd | Wholesale & retail | 2026 |
| Blanquos Limited | Wholesale & retail | 2025 |
| Blaze and Smoke Ltd | Hospitality | 2025 |
| Blaze Services Limited | Real estate | 2016 |
| Blazeco Ltd | Wholesale & retail | 2025 |
| Blazed Products Ltd | Wholesale & retail | 2025 |
| Blcs Properties Ltd | Real estate | 2026 |
| Bleached Limited | Administrative & support | 2025 |
| Bleajbu Service Ltd | Construction | 2025 |
| Blend 93 Ltd | Hospitality | 2020 |
| Blend Sports Ltd | Wholesale & retail | 2015 |
| Bless UP Kitchen Ltd | Hospitality | 2019 |
| Blessed Tours Limited | Administrative & support | 2024 |
| Blessing Care Ltd | Administrative & support | 2021 |
| Blessingyourscalp Limited | Other services | 2025 |
| Blessins UK Ltd | Wholesale & retail | 2021 |
| Blind Ambition (888) Ltd | Other services | 2018 |
| Blind Ambition Community Ltd | Administrative & support | 2018 |
| Blind Ambition Recruitment Ltd | Administrative & support | 2025 |
| Blind Ambition Support Ltd | Administrative & support | 2025 |
| Blinkcart Ltd | Wholesale & retail | 2025 |
| Blisk Detailing Ltd | Administrative & support | 2024 |
| Bliss Blaze Ltd | Wholesale & retail | 2024 |
| Bliss College UK Limited | Education | 2012 |
| Bliss Travel Limited | Transport & logistics | 1993 |
| Blissful Services Ltd | Transport & logistics | 2019 |
| Blissry Ltd | Wholesale & retail | 2025 |
| BLK CAB Coffee Ltd | Wholesale & retail | 2021 |
| Bln-Tmg -Drywall Ltd | Construction | 2024 |
| Blockchain Construction Limited | Construction | 2024 |
| Blogcreed Limited | Wholesale & retail | 2025 |
| Blogzio Ltd | Professional & scientific | 2025 |
| Bloke Knickers Ltd | Wholesale & retail | 2025 |
| Bloo Group Limited | Wholesale & retail | 2023 |
| Bloom Beyond Investments Limited | Real estate | 2025 |
| Bloom Boutique Official Ltd | Wholesale & retail | 2023 |
| Bloom Buy Trading Ltd | Wholesale & retail | 2026 |
| Bloom Mind Ltd | Wholesale & retail | 2025 |
| Bloom Room Skin Care & Laser Clinic Ltd | Other services | 2025 |
| Bloomberryco Ltd | Wholesale & retail | 2025 |
| Bloomingdale Services Ltd | Health & social care | 2026 |
| Bloomnest Ltd | Manufacturing | 2025 |
| Bloomtech Facilities Management Ltd | Administrative & support | 2024 |
| Blossom & Bloom Gardens Limited | Administrative & support | 2024 |
| Blossom Link Ltd | Health & social care | 2015 |
| Blossom Management Services Limited | Health & social care | 2019 |
| Blossom Trust | Health & social care | 2011 |
| Blow Beauty Salon Ltd | Administrative & support | 2023 |
| Bloxhall Investment Limited | Real estate | 2025 |
| Bloxhall RD Limited | Extraterritorial | 2020 |
| BLR LT Limited | Wholesale & retail | 2018 |
| BLU Creatives Ltd | Wholesale & retail | 2023 |
| BLU Kitchen Ltd | Hospitality | 2020 |
| Blud Ltd | Wholesale & retail | 2025 |
| Blue Axis Cart Limited | Wholesale & retail | 2025 |
| Blue Bird Advisory Ltd | Professional & scientific | 2025 |
| Blue Bird Lettings Ltd | Real estate | 2024 |
| Blue Chip Halal Meats Limited | Wholesale & retail | 2017 |
| Blue Crescent Ltd | Information & communication | 2022 |
| Blue Diamond Logistics and Recruitment Ltd | Transport & logistics | 2024 |
| Blue District Ltd | Professional & scientific | 2021 |
| Blue Eagle Enterprise Limited | Transport & logistics | 2024 |
| Blue EYE Productions Limited | Information & communication | 2002 |