| Beltempo Limited | Professional & scientific | 2013 |
| BEN Caplan Limited | Arts & recreation | 2024 |
| BEN Connolly Photography Ltd | Professional & scientific | 2024 |
| BEN Curran Project Management Ltd | Professional & scientific | 2020 |
| BEN Douglas Limited | Professional & scientific | 2023 |
| BEN Purple Limited | Professional & scientific | 2015 |
| Benchmark Staffing Solutions Ltd | Administrative & support | 2025 |
| Bendis Properties Limited | Real estate | 2013 |
| Benslow Music Enterprises Ltd | Hospitality | 2017 |
| Benslow Music Trust | Education | 1946 |
| Berry Events Ltd | Administrative & support | 2023 |
| Berry Inns Limited | Hospitality | 2005 |
| Bertie Homes Ltd | Real estate | 2026 |
| Bespoke Auto Interiors Limited | Wholesale & retail | 2009 |
| Best Merch Limited | Wholesale & retail | 2022 |
| Bethell Court Management Company Limited | Households | 2022 |
| Beverley Clarke Limited | Wholesale & retail | 2024 |
| Bews Electrical Limited | Wholesale & retail | 2007 |
| Bex.W Ltd | Hospitality | 2024 |
| Beyondtheninety Ltd | Professional & scientific | 2024 |
| BGB Films Limited | Information & communication | 2017 |
| BGC Limited | Financial services | 2022 |
| Bham Investments Limited | Real estate | 2025 |
| Bhandal Property Holdings Limited | Real estate | 2023 |
| Bianchi Furniture Limited | Wholesale & retail | 2003 |
| Bickley FS Ltd | Professional & scientific | 2022 |
| BID Beauty Ltd | Arts & recreation | 2025 |
| Bidwell Close Management Limited | Real estate | 1986 |
| Big AL Fresco Limited | Construction | 2026 |
| Big Impact Group Limited | Manufacturing | 2023 |
| Big Tree Investments Limited | Hospitality | 2015 |
| Big Tree Overland Limited | Hospitality | 2023 |
| BIM Morris-O'Neill Ltd | Professional & scientific | 2017 |
| Bingaguru Limited | Health & social care | 2015 |
| Binks Overseas Limited | Professional & scientific | 2015 |
| Bionicare Limited | Financial services | 2022 |
| Biovantic Medical Limited | Wholesale & retail | 2016 |
| Bipi Limited | Professional & scientific | 2000 |
| Birch & Blackthorn Ltd | Professional & scientific | 2026 |
| Birchmoor Investments Limited | Real estate | 2019 |
| Bismillah Garage Services Limited | Wholesale & retail | 2015 |
| Bita Motte Interiors Limited | Wholesale & retail | 2020 |
| Bitbran Limited | Information & communication | 2019 |
| Bite Back Oncology Services Limited | Professional & scientific | 2017 |
| Bizco Limited | Information & communication | 2009 |
| BJC Properties Limited | Real estate | 2003 |
| BJG Holdings Ltd | Wholesale & retail | 2025 |
| BKB Contracting Ltd | Construction | 2018 |
| BKM LDN Ltd | Wholesale & retail | 2025 |
| BL Intelligence Consulting Ltd | Professional & scientific | 2022 |
| Black GOO (UK) Limited | Financial services | 2022 |
| Black GOO Construction Limited | Construction | 2024 |
| Black GOO Leasehold Limited | Real estate | 2024 |
| Black GOO Management Limited | Professional & scientific | 2024 |
| Black GOO South East Limited | Administrative & support | 2024 |
| Black Magic Music Limited | Wholesale & retail | 2016 |
| Black Rock Property Consultancy Limited | Real estate | 2019 |
| Black Room Intelligence Ltd | Information & communication | 2023 |
| Black Squirrel UX Ltd | Information & communication | 2024 |
| Black Swan Management Group Ltd | Information & communication | 2018 |
| Blackhills Buildings Services Limited | Construction | 2024 |
| Blackjacket Ltd | Information & communication | 2018 |
| Blackmores (UK) Limited | Professional & scientific | 2004 |
| Blacksmith Mews Ltd | Real estate | 2022 |
| Blacksod Investments Limited | Real estate | 2023 |
| Blackstone Holdings Limited | Financial services | 2019 |
| Blake & Blake FS Limited | Real estate | 2017 |
| Blake Alexander Estates Limited | Real estate | 2022 |
| Blam Services Limited | Extraterritorial | 2020 |
| Blang Limited | Information & communication | 2006 |
| Blend Build Limited | Construction | 2021 |
| Blend Holdings Limited | Financial services | 2021 |
| Blend Technology Consultants Ltd | Information & communication | 2004 |
| Blinkin LAB Limited | Information & communication | 2006 |
| Blitz Cleaning Services (UK) Limited | Administrative & support | 2013 |
| BLM Plant Hire Limited | Administrative & support | 2022 |
| Blockchain Elephants Ltd | Wholesale & retail | 2023 |
| Blockchain Solutions Ltd | Financial services | 2015 |
| Bloom & Care Limited | Health & social care | 2017 |
| Bloom Babies Limited | Health & social care | 2024 |
| Bloom Homes & Developments Limited | Real estate | 2025 |
| Bloom Properties Investments Ltd | Real estate | 2021 |
| BLOOM91 Limited | Financial services | 2026 |
| Blossom Facials Limited | Other services | 2022 |
| Blossom Magic Designs Ltd | Wholesale & retail | 2021 |
| BLS Property Ltd | Real estate | 2024 |
| Bltm Limited | Health & social care | 2021 |
| Blue Ocean Assets Ltd | Extraterritorial | 2025 |
| Blue Opal Properties Limited | Hospitality | 2023 |
| Blue Planet Plumbing and Heating Ltd | Construction | 2020 |
| Blue Rose Landscapes Limited | Administrative & support | 2020 |
| Blue Space Estates Limited | Real estate | 2025 |
| Bluebadger Foods Ltd | Manufacturing | 2024 |
| Bluebloc Ltd | Information & communication | 2023 |
| Bluebrick Building Consultancy Ltd | Professional & scientific | 2017 |
| Bluebridge Management Limited | Real estate | 2014 |
| Bluefinch Ltd | Administrative & support | 2012 |
| Bluegrass Computer Services Limited | Information & communication | 1997 |
| Bluegrass Group Limited | Information & communication | 2016 |
| Bluestar Inc Limited | Extraterritorial | 2013 |