| Black Market Tattoo Ltd | Other services | 2019 |
| Black Nyangi Enaw (Legal Consultants) Ltd | Professional & scientific | 2025 |
| Black Pear Test Services Ltd | Information & communication | 2019 |
| Black Rabbit Bakery Ltd | Manufacturing | 2024 |
| Black Stone Softwares and Solutions Ltd | Information & communication | 2015 |
| Black Thunder Ltd | Information & communication | 2025 |
| Black TIE Boxing Promotions Ltd | Administrative & support | 2023 |
| Blackash Limited | Real estate | 2020 |
| Blackbird Consultants Limited | Professional & scientific | 2017 |
| Blackbird Crossroads Motors Ltd | Wholesale & retail | 2013 |
| Blackbird Pharmacy Limited | Wholesale & retail | 2000 |
| Blackbird Practice Limited | Health & social care | 2022 |
| Blackbird Precision Engineering Ltd | Professional & scientific | 2025 |
| Blackbird Property Holdings Ltd | Financial services | 2026 |
| Blackbird Property Surveyors Ltd | Professional & scientific | 2014 |
| Blackfire Technology Ltd | Information & communication | 2023 |
| Blacklist Creative Ltd | Information & communication | 2015 |
| Blackridge Crest Holdings Ltd | Real estate | 2026 |
| Blackrock Consultancy Services Ltd | Wholesale & retail | 2016 |
| Blackshole Farm (Dartford) Development Limited | Real estate | 2013 |
| Blackthorn Investments Ltd | Administrative & support | 2010 |
| Blackthorn Property Group Ltd | Real estate | 2025 |
| Blackways Limited | Real estate | 2010 |
| Blackwell Building Limited | Construction | 2000 |
| Blackwood Electrical Ltd | Construction | 2026 |
| Blade of Gold Leicester Limited | Other services | 2023 |
| Bladek Ltd | Transport & logistics | 2012 |
| Blaggan Limited | Real estate | 2021 |
| Blake Beardsley Limited | Financial services | 2024 |
| Blake East Ltd | Professional & scientific | 2024 |
| Blake Edwards & Co. Ltd | Other services | 2023 |
| Blake's Enterprise's & Homes Ltd | Real estate | 2022 |
| Blakemore Construction Limited | Professional & scientific | 2019 |
| Blakeney Timeshare Management Limited | Hospitality | 1988 |
| Blakewater Consultancy Limited | Professional & scientific | 2026 |
| Blanco Enterprises Limited | Real estate | 2020 |
| Bland Road Ltd | Real estate | 2025 |
| Blanktag Media Ltd | Professional & scientific | 2022 |
| Blanque Canvas Ltd | Manufacturing | 2023 |
| Blanson Limited | Manufacturing | 2005 |
| Blauberg UK Limited | Manufacturing | 1999 |
| Blax Limited | Construction | 2025 |
| Blazedem Records Ltd | Information & communication | 2023 |
| Blazin Bird UK Ltd | Hospitality | 2023 |
| BLE Properties Limited | Construction | 2013 |
| Blem Limited | Wholesale & retail | 2017 |
| Blenco Bespoke Ltd | Manufacturing | 2025 |
| Blend Leicester Ltd | Arts & recreation | 2025 |
| Bless Trading Limited | Wholesale & retail | 2015 |
| Blessden Healthcare Solutions Limited | Health & social care | 2016 |
| Blesskay Logistics Ltd | Transport & logistics | 2025 |
| Blickglen Lifts Ltd | Manufacturing | 1979 |
| Bling Phones & Accessories Ltd | Wholesale & retail | 2005 |
| Blink OMS Limited | Information & communication | 2024 |
| Bliss & Grace Enterprise Ltd | Wholesale & retail | 2026 |
| Bliss Anchorpoint Ltd | Health & social care | 2026 |
| Bliss DRY Cleaning Services Limited | Wholesale & retail | 2013 |
| Bliss Healthcare Services Ltd | Health & social care | 2019 |
| Bliss Travel Group Ltd. | Administrative & support | 1992 |
| Blissful Journey Ltd | Other services | 2021 |
| Blissfull Services (UK) Limited | Arts & recreation | 2013 |
| Blitz UK PVT Ltd | Wholesale & retail | 2023 |
| Blizzard Management Limited | Real estate | 2014 |
| BLK Brgr Limited | Hospitality | 2025 |
| Bllu PIN Limited | Hospitality | 2026 |
| BLOC22 Ltd | Wholesale & retail | 2020 |
| Block Chain Staffing Public Limited | Information & communication | 2025 |
| Block Foods Limited | Manufacturing | 2023 |
| Blockchain Distribution Ltd | Other services | 2018 |
| Blocked Drain MID Ltd | Water & waste | 2025 |
| Bloclite Blinds Ltd | Wholesale & retail | 2024 |
| Blodi Investment Ltd | Real estate | 2026 |
| Blokpay Limited | Information & communication | 2025 |
| Blokpay UK Limited | Information & communication | 2025 |
| Blondix 88 Ltd | Transport & logistics | 2026 |
| Blondix Limited | Transport & logistics | 2022 |
| Bloo Moon Limited | Financial services | 2013 |
| Bloom & Brush Ltd | Construction | 2025 |
| Bloom Accounting Limited | Extraterritorial | 2021 |
| Bloom Basket Ltd | Information & communication | 2025 |
| Bloom Catering & Events Management Ltd | Hospitality | 2021 |
| Bloom Weddings Ltd | Professional & scientific | 2018 |
| Bloom Wellbeing & Counselling Limited | Professional & scientific | 2025 |
| Bloomax Technology Limited | Information & communication | 2025 |
| Bloomkubes Limited | Agriculture & fishing | 2019 |
| Blooms Management Services Ltd | Construction | 2021 |
| Bloomsburry 88 Limited | Real estate | 2022 |
| Bloom’S Gym Limited | Wholesale & retail | 2025 |
| Bloom’S Kitchen Limited | Manufacturing | 2025 |
| Bloom’S LAB Ltd | Manufacturing | 2026 |
| BLOPES26 Ltd | Transport & logistics | 2026 |
| Blossom & Co Holdings Ltd | Financial services | 2025 |
| Blossom Adult Care Ltd | Health & social care | 2026 |
| Blossom Children Care Ltd | Health & social care | 2026 |
| Blossom Commerce Limited | Information & communication | 2022 |
| Blossom Perfumery Ltd | Manufacturing | 2020 |
| Blossom Yoga Limited | Extraterritorial | 2011 |
| Blossoms Limited | Education | 1999 |
| Blossoms Property Ltd | Construction | 2024 |
| BLP Global Ltd | Wholesale & retail | 2023 |