| Bluefuse Electrical Ltd | Construction | 2026 |
| Blueline Developments Limited | Construction | 2024 |
| Bluemeadow Holdings Ltd | Real estate | 2024 |
| Blueocean Development AI Ltd | Information & communication | 2024 |
| Blueprint Arts Foundation CIC | Arts & recreation | 2007 |
| Blues Electrical Services Ltd | Construction | 2018 |
| Bluetech Consulting Limited | Information & communication | 2014 |
| Blush Health & Beauty Ltd | Other services | 2011 |
| BMG Property Development Ltd | Real estate | 2021 |
| Bmjs Physiotherapy Consultancy Limited | Health & social care | 2015 |
| BMS International Ltd | Construction | 2019 |
| BMT Construction Limited | Construction | 2020 |
| Bnbl Limited | Hospitality | 2015 |
| BOB Booker Associates Limited | Professional & scientific | 2010 |
| BOB Rains Wealth Management Limited | Professional & scientific | 2012 |
| Boba Town Ltd | Hospitality | 2021 |
| Boby Trans Limited | Transport & logistics | 2017 |
| Body Alignment Expert Ltd | Administrative & support | 2018 |
| Body Beautiful Nutrition Ltd | Other services | 2015 |
| Body Bronzee Ltd | Other services | 2015 |
| Boescakes Ltd | Other services | 2021 |
| BOG BM Ltd | Transport & logistics | 2020 |
| Bog'Art Glazing Ltd | Construction | 2015 |
| Bogdan Construction Ltd | Construction | 2015 |
| Bola Samuel Consulting Limited | Professional & scientific | 2024 |
| Bolaj UK Ltd | Administrative & support | 2011 |
| Bolandia Consult Limited | Information & communication | 2008 |
| Bolaog Limited | Extraterritorial | 2019 |
| Boldrise UK Ltd | Wholesale & retail | 2025 |
| Boleyn Electrical Services Ltd | Construction | 2008 |
| Bombay Hair UK Ltd | Wholesale & retail | 2014 |
| Bombay Tiffin Northfleet Ltd | Hospitality | 2018 |
| Bond & Hoxton Ltd | Professional & scientific | 2021 |
| Bonifacio Investments Ltd | Wholesale & retail | 2022 |
| Bonita Beauty by Sammie Limited | Other services | 2022 |
| Bonum Home Ltd | Wholesale & retail | 2024 |
| Bookkeepers International Group Ltd | Professional & scientific | 2024 |
| Boosta Ltd | Manufacturing | 2026 |
| Boosted Weave Ltd | Manufacturing | 2025 |
| Borough Drainage Services Ltd | Water & waste | 2024 |
| Borough Pest Control Ltd | Professional & scientific | 2021 |
| Bossman Brands Ltd | Manufacturing | 2019 |
| Botin Limited | Professional & scientific | 2014 |
| Boudicca Blue Bodyart Limited | Administrative & support | 2009 |
| Boughton Investments Limited | Real estate | 2026 |
| Bourne Browne Ltd | Administrative & support | 2018 |
| Bows to Balloons Ltd | Wholesale & retail | 2020 |
| Boxes Ltd | Information & communication | 2022 |
| Boyan Transport 2017 Ltd | Transport & logistics | 2017 |
| Boyson Builders Ltd | Construction | 2023 |
| Boyson Services Roofing and Building Ltd | Construction | 2024 |
| BPS Advisory Ltd | Professional & scientific | 2026 |
| Brackenside Ltd | Health & social care | 2015 |
| Braconi Electrics Ltd | Construction | 2025 |
| Bradbury Property Developments Ltd | Real estate | 2016 |
| Bradley Ventures Limited | Health & social care | 2006 |
| Bradley,Vann Limited | | 1962 |
| Bradshaw Electrical Solutions Limited | Construction | 2021 |
| Brahm Construction Limited | Construction | 2024 |
| Braika Trans Ltd | Transport & logistics | 2021 |
| Brain Excel Academy Ltd | Education | 2021 |
| Braitch Transport Ltd | Transport & logistics | 2021 |
| Bramley Trading Ltd | Financial services | 2004 |
| Brandmaker Ltd | Professional & scientific | 2026 |
| Brar Haulage Ltd | Transport & logistics | 2025 |
| Brar.Sterling Limited | Hospitality | 2025 |
| Brar.Sterling-Heights Limited | Real estate | 2014 |
| Bravo Facilities Management Limited | Administrative & support | 2025 |
| Bread + Butter Limited | Professional & scientific | 2005 |
| Breakthrough Masterclasses Ltd | Administrative & support | 2025 |
| Breakthrough Ministries International CIC | Education | 2025 |
| Breeze IT Solutions Ltd | Information & communication | 2011 |
| Bremont Weir Limited | Financial services | 2021 |
| Brenwards Limited | Construction | 1983 |
| Breslin Holdings Limited | Financial services | 2025 |
| Breslin Property Limited | Real estate | 2023 |
| Breway Limited | Construction | 2009 |
| Brewster Financial Planning Limited | Financial services | 2009 |
| Brick Masters Construction Ltd | Construction | 2025 |
| Bricksworth Mortgage Company Ltd | Financial services | 2025 |
| Brics Solutions Limited | Construction | 2014 |
| Bride & Groom (Kent) Limited | Wholesale & retail | 2009 |
| Bridge Ways Lane Ltd | Other services | 2018 |
| Bridgepath Solutions Limited | Construction | 2024 |
| Bridges Day Nursery Limited | Education | 2024 |
| Bridgeview Investments Limited | Real estate | 2013 |
| Bright Light AKA Ltd | Health & social care | 2021 |
| Bright Lights Agcy Limited | Administrative & support | 2024 |
| Bright Skies Pet Services Limited | Other services | 2017 |
| Bright Star PCO Ltd | Administrative & support | 2026 |
| Bright Touch Services Ltd | Administrative & support | 2025 |
| Bright Vision Group Limited | Construction | 2022 |
| Bright Vision Interior Limited | Construction | 2020 |
| Brightbuild Solutions Ltd | Manufacturing | 2019 |
| Brighter Horizonz Limited | Health & social care | 2024 |
| Brightforce Resources Ltd | Administrative & support | 2025 |
| Brightlink Logistics Ltd | Transport & logistics | 2025 |
| Brightstar Business Ltd | Construction | 2024 |
| Bristone Precast Ltd | Manufacturing | 2023 |
| Brit Sidecar Championship Limited | Arts & recreation | 2025 |