| Biovision Consultants Limited | Professional & scientific | 2008 |
| Birchwood Concrete Products Limited | Professional & scientific | 2000 |
| Birchwood Omnia Limited | Financial services | 2000 |
| Birchwood Priory Medical Limited | Health & social care | 2016 |
| Birdi Entrepreneur Ltd | Extraterritorial | 2021 |
| Birdi Estates Ltd | Real estate | 2025 |
| Biriyani Hutt Ltd | Hospitality | 2023 |
| Bismillah BM Grill and Dessert Limited | Hospitality | 2025 |
| Bisque-It Studio Ltd | Hospitality | 2025 |
| Biteswelove Ltd | Hospitality | 2021 |
| Bits & Bliss Ltd | Wholesale & retail | 2025 |
| BIZ Homes (Bucks) Limited | Real estate | 2018 |
| BJ Properties Maidenhead Limited | Real estate | 2025 |
| BJH Investments Limited | Administrative & support | 2017 |
| BK Data Solutions Limited | Information & communication | 2018 |
| BK Land and Estates Limited | Real estate | 2021 |
| BKM Artists Ltd | Information & communication | 2019 |
| BKM Publishing Limited | Information & communication | 2026 |
| Blacbridge Ltd | Real estate | 2023 |
| Black Bull C.P.M Ltd | Wholesale & retail | 2025 |
| Black Goldfish Ltd | Professional & scientific | 2016 |
| Black Mamba Marketing & Events Ltd | Hospitality | 2018 |
| Black Mountain Pubs Ltd | Hospitality | 2007 |
| Black Reeve Limited | Construction | 2004 |
| Blackburne Holdings Limited | Financial services | 2024 |
| Blackdowne Coaching and Consultancy Limited | Professional & scientific | 2015 |
| Blackfox Solutions Limited | Administrative & support | 2010 |
| Blackingstone Consulting Ltd | Professional & scientific | 2025 |
| Blake & Bull Ltd | Manufacturing | 2017 |
| Blake Solutions Ltd | Water & waste | 2024 |
| Blakeney Associates Limited | Real estate | 1991 |
| Blarghour Wind Farm Limited | Energy | 2014 |
| Blenheim Capital London Limited | Administrative & support | 2015 |
| Bleriot Wines Limited | Wholesale & retail | 2014 |
| Blgs Core Ltd | Wholesale & retail | 2025 |
| Blooming British Ltd | Wholesale & retail | 2022 |
| Bloomsbury Accountancy Limited | Professional & scientific | 2003 |
| Bloomsburys Limited | Professional & scientific | 2007 |
| Blow Media Limited | Information & communication | 2009 |
| Bloōme Aesthetics Limited | Other services | 2026 |
| Blslandscapes Ltd | Administrative & support | 2026 |
| Blue Chip Global Limited | Professional & scientific | 2016 |
| Blue Lagoon Operations Limited | Information & communication | 2026 |
| Blue Light Partnership (ASP) Holdings Limited | Financial services | 2012 |
| Blue Light Partnership (ASP) Limited | Financial services | 2012 |
| Blue Robin Homes Limited | Real estate | 2025 |
| Blue Sky Dwellings Limited | Real estate | 2025 |
| Blue Square Data MK Limited | Extraterritorial | 2009 |
| Blue Square Data Services Limited | Extraterritorial | 2009 |
| Blueboy Music Limited | Information & communication | 2021 |
| Bluechain International Limited | Information & communication | 2017 |
| Bluechain Payments Limited | Financial services | 2017 |
| Bluechain Technologies Limited | Information & communication | 2017 |
| Bluecrown Consulting Limited | Professional & scientific | 2010 |
| Bluefish Software Limited | Information & communication | 2008 |
| Bluerock Estates Limited | Real estate | 2016 |
| Bluewomen CIC | Wholesale & retail | 2025 |
| Blvk Properties Ltd | Real estate | 2026 |
| BMS Building Limited | Construction | 2016 |
| BMS Projects Limited | Construction | 2023 |
| BMS Property Management Ltd | Real estate | 2024 |
| Bmsi EOT Limited | Professional & scientific | 2022 |
| Bmvh (UK) Limited | Wholesale & retail | 2020 |
| BN Vehicles Ltd | Wholesale & retail | 2023 |
| Bnca Ltd | Professional & scientific | 2025 |
| BNY Orai'N Ltd | Information & communication | 2020 |
| Bockmer Livery Stables Limited | Agriculture & fishing | 2020 |
| BOD Garments Limited | Administrative & support | 2018 |
| Bodacious British Beancounters Ltd | Information & communication | 2022 |
| Boddledale Holdings Limited | Real estate | 2021 |
| Boddledale Investments Limited | Real estate | 2022 |
| Boddy-Mclindon Limited | Administrative & support | 2025 |
| Body of Work Media CIC | Information & communication | 2025 |
| Body of Work Productions Ltd | Information & communication | 2025 |
| Body Ventures Limited | Information & communication | 2004 |
| Bodymanoeuvres Ltd | Health & social care | 2019 |
| Bodyworks W1 Limited | Health & social care | 2009 |
| Boemen Business Solutions Ltd | Professional & scientific | 2025 |
| Bohome Interiors Limited | Professional & scientific | 2023 |
| Bold Clarity Ltd | Education | 2014 |
| Boldfolk Limited | Professional & scientific | 2025 |
| Bolt-On a Walk Ltd | Agriculture & fishing | 2023 |
| Bombay Story Limited | Hospitality | 2025 |
| Bondgate Advisory Limited | Real estate | 2012 |
| Bonds Packaging Limited | Hospitality | 2016 |
| Bonustower Limited | Households | 2000 |
| Boonanas Limited | Wholesale & retail | 2014 |
| Boost Enterprises Ltd | Administrative & support | 2017 |
| Booth Decorators Limited | Construction | 2026 |
| Bora Group London Ltd | Real estate | 2021 |
| Border BIT Ltd | Wholesale & retail | 2016 |
| Boss Birdi Ltd | Wholesale & retail | 2018 |
| Boss MAN Food & Wine Ltd | Wholesale & retail | 2021 |
| Boston Semi Equipment Europe Ltd. | Manufacturing | 2004 |
| Boswell Electrical Works Limited | Construction | 2016 |
| Boswell Healthcare Ltd | Health & social care | 2006 |
| Boulter & Associates Limited | Professional & scientific | 2018 |
| Bouncy Baileys Ltd | Administrative & support | 2016 |
| Boundary Metal Limited | Extraterritorial | 2008 |
| Bourne Building Services Limited | Construction | 2006 |