| Blizzard Services Ltd | Construction | 2018 |
| BLK Enterprises Limited | Wholesale & retail | 2020 |
| Blmtlss Global Ltd | Information & communication | 2020 |
| Block 1 Management Company Limited | Extraterritorial | 2024 |
| Block 5 Leaseholders Company Limited | Real estate | 2024 |
| Blooms Accountancy Ltd. | Professional & scientific | 2013 |
| Blue Arrow Technology Ltd | Professional & scientific | 2022 |
| Blue Direct Limited | Administrative & support | 1999 |
| Blue Direct Services LLP | | 2011 |
| Blue Flame Appliances Ltd | Construction | 2025 |
| Blue Heart Clinics Ltd | Extraterritorial | 2014 |
| Blue Mountain Accountants Ltd | Professional & scientific | 2026 |
| Blue Robot Limited | Information & communication | 2014 |
| Blue Sky HR & Change Consulting Ltd | Administrative & support | 2021 |
| Blue Vista Property Limited | Real estate | 2025 |
| Blue York Limited | Hospitality | 2019 |
| Blueberryz Lets Ltd | Real estate | 2021 |
| Bluegate Consulting Ltd | Administrative & support | 2019 |
| Blues Events Ltd | Arts & recreation | 2021 |
| Blueshark Investments Limited | Real estate | 2019 |
| Blupebble UK Limited | Extraterritorial | 2022 |
| BMD Plastering Limited | Construction | 2019 |
| BMF Logistic Limited | Transport & logistics | 2021 |
| BN Contractors Limited | Construction | 2018 |
| Boa-Lane Ltd | Administrative & support | 2011 |
| BOB T Ltd | Construction | 2026 |
| Bobby and JEY Trading Ltd | Wholesale & retail | 2025 |
| Body Basics DUN Limited | Health & social care | 2007 |
| BOL Consulting Limited | Professional & scientific | 2017 |
| Boldthorn Trade Ltd | Wholesale & retail | 2021 |
| Bombay Kitchen Luton Limited | Hospitality | 2025 |
| Bond App Ltd | Information & communication | 2026 |
| Bondhu Limited | Hospitality | 2020 |
| Bongoan Ltd | Hospitality | 2008 |
| Boogie Case Limited | Manufacturing | 2015 |
| Borders Development Company Ltd | Construction | 2015 |
| Botstrans Limited | Construction | 2010 |
| Bourke & Stewart Limited | Administrative & support | 2012 |
| Bowerbirdy Ltd | Hospitality | 2016 |
| Boxed and Bound Ltd | Transport & logistics | 2025 |
| Boxhedge Limited | Hospitality | 1998 |
| Bozo Limited | Hospitality | 2025 |
| BPL Consulting Limited | Information & communication | 2016 |
| BPM Consultancy Limited | Professional & scientific | 2007 |
| BR Payroll Services 2025 Limited | Administrative & support | 2025 |
| Braandy Healthcare Ltd | Health & social care | 2024 |
| Brambly View Limited | Hospitality | 2025 |
| Bramfort Limited | Hospitality | 2024 |
| Bramingham Wood Limited | Construction | 2022 |
| Branch OUT Forest School Limited | Education | 2019 |
| Brand Skillings Limited | Professional & scientific | 2010 |
| Brand Wizz Ltd | Professional & scientific | 2024 |
| Branss Ltd | Wholesale & retail | 2019 |
| Brass Property Limited | Real estate | 2025 |
| Breach Repairer Ministries | Other services | 2015 |
| Break Properties Ltd | Real estate | 2018 |
| Breakridge Limited | Professional & scientific | 2018 |
| Breath and Voice Ltd | Arts & recreation | 2022 |
| Breathe Green Ltd | Professional & scientific | 2021 |
| Breight Limited | Wholesale & retail | 2014 |
| Brendan Mccormick Events AV Ltd | Manufacturing | 2003 |
| Brendan the Chilli MAN Limited | Manufacturing | 2020 |
| Bridgewater Homes (Harpenden) Ltd | Construction | 2016 |
| Bridgewater Homes (Leighton Buzzard) Ltd | Construction | 2020 |
| Bright Education Overseas Co. Ltd | Professional & scientific | 2018 |
| Bright Haven Property Investments Ltd | Real estate | 2026 |
| Brighter Intelligence Labs Ltd | Information & communication | 2026 |
| Brighter Software Ltd. | Information & communication | 2013 |
| Brightside Rentals Limited | Real estate | 2017 |
| Brightwood Homes (Harpenden) Limited | Construction | 2015 |
| Brilliant Food & Wine Limited | Wholesale & retail | 2016 |
| Brilliant Publications Limited | Information & communication | 1999 |
| Brinza Ltd | Transport & logistics | 2025 |
| Brirbuilds Limited | Wholesale & retail | 2026 |
| Brit Engineering Services Ltd | Administrative & support | 2016 |
| Britain GOT Hungry Ltd | Hospitality | 2025 |
| Britannia Estates (Luton) Limited | Extraterritorial | 1972 |
| Britianwholesale Ltd | Other services | 2023 |
| British Association for Sustainable Sport | Administrative & support | 2013 |
| Britishmax Limited | Administrative & support | 2013 |
| Britt-Bau Ltd | Construction | 2019 |
| BRK Construction Ltd | Construction | 2017 |
| BRO Waste Management Ltd | Water & waste | 2024 |
| Broad Fort Limited | Hospitality | 2023 |
| Broadfinch Limited | Real estate | 2020 |
| Bromfield Engineering Limited | Professional & scientific | 2001 |
| Brooke Legal Ltd | Professional & scientific | 2019 |
| Brookland Education Consultancy Limited | Professional & scientific | 2024 |
| Brooks Carter Limited | Information & communication | 2026 |
| Broomstick Developments Ltd | Real estate | 2024 |
| Brown Bear Landscaping Ltd | Administrative & support | 2024 |
| Brown Rigging Ltd | Information & communication | 2017 |
| Brown-It Solution Services Limited | Information & communication | 2019 |
| BRS Brickwork Limited | Construction | 2018 |
| Brsaleh Ltd | Wholesale & retail | 2024 |
| Brugo Homes Ltd | Real estate | 2025 |
| BS1 Holdings Ltd | Real estate | 2023 |
| Bsukltd Limited | Transport & logistics | 2017 |
| BT Capital Ltd | Other services | 2020 |
| Buckers Rail Ltd | Construction | 2015 |