| Bjou Capital Limited | Hospitality | 2019 |
| BJP Interiors Ltd | Construction | 2016 |
| BK Fortune Group Ltd | Real estate | 2025 |
| BK Lighting Ltd | Administrative & support | 2017 |
| BK Mallorca Ltd | Construction | 2006 |
| BK Motors Cardiff Limited | Wholesale & retail | 2021 |
| BK Star Healthcare Ltd | Administrative & support | 2023 |
| BK Top Cars Ltd | Wholesale & retail | 2023 |
| BK8 Limited | Arts & recreation | 2025 |
| BKG Leathers Limited | Manufacturing | 2025 |
| Bkgtn Ltd | Wholesale & retail | 2025 |
| BKL Global Ltd | Wholesale & retail | 2025 |
| BKR Brothers Ltd | Wholesale & retail | 2025 |
| BKR Holdings LLP | | 2021 |
| BKS Cupboard Ltd | Wholesale & retail | 2019 |
| BKS Removals Ltd | Transport & logistics | 2019 |
| BKS UK Soloutions Ltd | Construction | 2019 |
| BL Global Consultancy Services Ltd | Professional & scientific | 2021 |
| BL Leisure Limited | Other services | 2018 |
| BL Luxury Rentals Ltd | Administrative & support | 2025 |
| BL Recycling Limited | Wholesale & retail | 2019 |
| BL Transport Limited | Administrative & support | 2013 |
| Blac Properties Limited | Real estate | 2022 |
| Black & Beech Ltd | Wholesale & retail | 2021 |
| Black & Gold Natural Indulgence Ltd | Wholesale & retail | 2020 |
| Black and Ethnic Xcellence CIC | Information & communication | 2021 |
| Black Angel Ltd | Other services | 2023 |
| Black Avex Ltd | Hospitality | 2017 |
| Black Beacon Ltd | Administrative & support | 2019 |
| Black Bear Projects Ltd | Construction | 2017 |
| Black Brick Studio Ltd | Professional & scientific | 2023 |
| Black Bronze Ltd | Professional & scientific | 2018 |
| Black CAB Cafe and Shawarma Souls Limited | Hospitality | 2026 |
| Black Castle Global Ltd | Wholesale & retail | 2025 |
| Black Cat Print Club Limited | Arts & recreation | 2023 |
| Black Cat Sound Ltd | Information & communication | 2021 |
| Black Charcoal Media Ltd | Information & communication | 2023 |
| Black Country Light and Sound Limited | Arts & recreation | 2017 |
| Black Country Orthodontics Ltd | Health & social care | 2014 |
| Black Diamond Marketing Ltd | Professional & scientific | 2019 |
| Black Diamond Topaz Ltd | Wholesale & retail | 2025 |
| Black Dragon Engineering Limited | Construction | 2019 |
| Black Dragon Studios Ltd | Information & communication | 2018 |
| Black Events Agency Limited | Other services | 2019 |
| Black EYE Properties Limited | Real estate | 2025 |
| Black Flower Souls CYF | Wholesale & retail | 2025 |
| Black Fortress Security Limited | Administrative & support | 2025 |
| Black FOX Holdings Ltd | Financial services | 2025 |
| Black Gold Productions Limited | Manufacturing | 2020 |
| Black Hair TIE Ltd | Wholesale & retail | 2026 |
| Black Impulse Ltd. | Extraterritorial | 2015 |
| Black INK Cinema Ltd | Information & communication | 2020 |
| Black Knight Tinting Limited | Professional & scientific | 2016 |
| Black Knights Marketing Limited | Professional & scientific | 2021 |
| Black Krown Ltd | Professional & scientific | 2025 |
| Black Lion Roofing Ltd | Construction | 2020 |
| Black Lion Wealth Management Limited | Financial services | 2018 |
| Black List Escapes Ltd | Administrative & support | 2025 |
| Black Magnolia Ltd | Extraterritorial | 2017 |
| Black Mountain Catering Ltd | Hospitality | 2025 |
| Black Mountain Technology Group Ltd | Information & communication | 2025 |
| Black Opal Organisation Ltd | Hospitality | 2022 |
| Black Pearl Care Solution Ltd | Health & social care | 2022 |
| Black Pearl Stays Limited | Hospitality | 2023 |
| Black Phantom Limited | Extraterritorial | 2019 |
| Black Rain Limited | Information & communication | 2025 |
| Black Rock Bristol Limited | Hospitality | 2019 |
| Black Rock Tavern Limited | Hospitality | 2019 |
| Black Sheep Properties Ltd | Real estate | 2023 |
| Black Smoke Limited | Wholesale & retail | 2018 |
| Black Spear Ltd | Construction | 2024 |
| Black Stars Global Holdings Limited | Extraterritorial | 2021 |
| Black Steel Projects LLP | | 2022 |
| Black Tide BIO Limited | Information & communication | 2025 |
| Black TIE Bartenders Ltd | Hospitality | 2017 |
| Black Yolk Limited | Construction | 2026 |
| BLACK4ME Ltd | Wholesale & retail | 2025 |
| Blackberry Cars Limited | Transport & logistics | 2013 |
| Blackbird Visuals Ltd | Information & communication | 2022 |
| Blackburn Loxley Limited | Real estate | 2008 |
| Blackburn Pinnacle Ltd | Wholesale & retail | 2021 |
| Blackcrest Facilities Group Limited | Administrative & support | 2026 |
| Blackcrest Holdings Ltd | Financial services | 2026 |
| Blackett Road Surfacing Limited | Wholesale & retail | 1988 |
| Blackflamingo Beauty Ltd | Wholesale & retail | 2022 |
| Blackfly Consulting Ltd | Administrative & support | 2017 |
| Blackforest Enterprises Ltd | Administrative & support | 2017 |
| Blackfox Partners Ltd | Financial services | 2025 |
| Blackfriars Industries Ltd | Professional & scientific | 2025 |
| Blackgear Ltd | Transport & logistics | 2017 |
| Blackhawk London Ltd | Administrative & support | 2010 |
| Blackhawkagency Ltd | Professional & scientific | 2023 |
| Blackhoopoe Ltd | Wholesale & retail | 2025 |
| Blackline Academy Ltd | Wholesale & retail | 2025 |
| Blackmarket Trading Ltd | Wholesale & retail | 2020 |
| Blackmoor Associates Limited | Professional & scientific | 2017 |
| Blackmore Group Ltd | Professional & scientific | 2016 |
| Blackoak Meded Ltd | Education | 2023 |
| Blackout Detailing Ltd | Wholesale & retail | 2020 |
| Blackpool Hotel Investment Limited | Households | 2021 |