| Bandol Capital Limited | Financial services | 2014 |
| Banes Jackson Limited | Real estate | 1999 |
| Bange Building Services Limited | Construction | 2002 |
| Bange Construction Limited | Construction | 2024 |
| Bangladeshi Housing Watford Ltd | Real estate | 2025 |
| Bankside Commercial Limited | Professional & scientific | 2001 |
| Bannerman Accounting Ltd | Professional & scientific | 2015 |
| Banqy Ltd | Professional & scientific | 2020 |
| Bantu Holdings Ltd | Professional & scientific | 2006 |
| Bantu Investments Ltd | Financial services | 2006 |
| Banyan Tree International Ltd | Wholesale & retail | 2023 |
| BAP London Limited | Administrative & support | 2019 |
| Bapashri Services Limited | Construction | 2013 |
| Bar APG Scheme Corporate Trustee Limited | Financial services | 2017 |
| Bar H Limited | Hospitality | 2019 |
| Barbera and Partners Ltd | Professional & scientific | 2021 |
| Barbless Flies Limited | Wholesale & retail | 2016 |
| Barclay & Cowie of URY Limited | Real estate | 2019 |
| Barco Money Ltd | Information & communication | 2026 |
| Bardo Openvizor Limited | Arts & recreation | 2006 |
| Barean Ltd | Real estate | 2022 |
| Barfordex Holdings Ltd | Real estate | 2025 |
| Bargain Basement Centre Limited | Extraterritorial | 2006 |
| Bargain Dentist.Com Limited | Health & social care | 2006 |
| Bargo Steel Ltd | Wholesale & retail | 2021 |
| Bari London Ltd | Wholesale & retail | 2024 |
| Barland Services Ltd | Administrative & support | 1999 |
| Barley Bygrave Limited | Professional & scientific | 2024 |
| Barnes Leisure Ltd | Other services | 2016 |
| Barnett Care Homes Ltd | Health & social care | 2019 |
| Barobertsongs Ltd | Information & communication | 2017 |
| Baron Barbers Ltd | Other services | 2025 |
| Barracuda Bushey Limited | Hospitality | 2016 |
| Barrett Industrial Limited | Other services | 2006 |
| Barrington UK Consultancy Ltd | Professional & scientific | 2017 |
| Barry Builders Limited | Construction | 2023 |
| Barsoaga-Marin Ltd | Wholesale & retail | 2019 |
| Bartmax Limited | Construction | 2018 |
| Barton Dental Centre Limited | Health & social care | 2010 |
| Barton Electrics Ltd | Construction | 2019 |
| Barzel Steel Ltd | Construction | 2012 |
| Basal Holdings Ltd | Health & social care | 2024 |
| Basco Accounts Services Limited | Administrative & support | 1990 |
| Base Control Systems Ltd | Manufacturing | 2016 |
| Base LAB Studios Ltd | Information & communication | 2020 |
| Base Maintenance Services Ltd | Construction | 2019 |
| Base Venture Consultancy Ltd | Professional & scientific | 2025 |
| Base Venture Ltd | Real estate | 2021 |
| Baselevel Labs Ltd | Professional & scientific | 2025 |
| Baseline Technologies Ltd | Wholesale & retail | 2014 |
| Basements London Ltd | Construction | 2023 |
| Bash Property Holdings Ltd | Real estate | 2025 |
| Bashabari Ltd | Real estate | 2021 |
| Bass Place Limited | Wholesale & retail | 2016 |
| Bassi Consulting Limited | Information & communication | 2005 |
| Bastion Logistics Limited | Transport & logistics | 2020 |
| Bastion Renovations Limited | Construction | 2023 |
| Basway Properties Limited | Real estate | 2020 |
| Batach Solutions Ltd | Professional & scientific | 2020 |
| Batch Services Limited | Administrative & support | 2025 |
| Batshon Ltd | Real estate | 2016 |
| Batter and Splatter Ltd | Manufacturing | 2020 |
| Batterytick Ltd | Wholesale & retail | 2026 |
| Batuna Accountants Ltd | Professional & scientific | 2021 |
| Bauddha Ltd | Information & communication | 2023 |
| Bava Logistics Limited | Transport & logistics | 2026 |
| Baverstock Developments Ltd | Real estate | 2025 |
| Bawd Tyre Associates Limited | Information & communication | 2014 |
| Baxter Fell & Co.Limited | | 1937 |
| Baxter Harris Logistics Ltd | Transport & logistics | 2022 |
| Bay Engineering Consultancy Ltd | Professional & scientific | 2022 |
| Bayes Studio Ltd | Wholesale & retail | 2026 |
| BAZ Property Investments Ltd | Real estate | 2021 |
| BAZAR23 Ltd | Construction | 2023 |
| BB (UK) Ltd | Other services | 1997 |
| BB Construction Engineering Ltd | Construction | 2017 |
| BB Designs Europe Limited | Wholesale & retail | 2003 |
| BB Jewellery Online Limited | Wholesale & retail | 2021 |
| BB Printers Ltd | Manufacturing | 2022 |
| Bbda Automotive Limited | Wholesale & retail | 2025 |
| BBH Plumbing & Heating Ltd | Construction | 2017 |
| BBS Construction Limited | Construction | 2023 |
| BC Novate Ltd | Wholesale & retail | 2025 |
| BCB Property Ltd | Real estate | 2007 |
| Bcli Contract Services Limited | Information & communication | 2019 |
| BCM Europe Limited | Financial services | 2015 |
| Bcoc Limited | Administrative & support | 2023 |
| BCR Motors Ltd | Wholesale & retail | 2025 |
| BD & CCA Ltd | Transport & logistics | 2017 |
| Bdellium Trading Company Limited | Wholesale & retail | 2015 |
| BDR Entertainment Ltd | Arts & recreation | 2023 |
| BDW Investments Limited | Real estate | 2022 |
| BE Education Limited | Education | 2015 |
| BE Mint Ltd | Real estate | 2019 |
| BE Residential Holdings Ltd | Real estate | 2026 |
| BE Unexpected Ltd | Administrative & support | 2017 |
| BE Your Own Date Ltd | Education | 2021 |
| Beach Estates Limited | Real estate | 2020 |
| Beach Haven Ltd | Information & communication | 2017 |
| Beachclub Ltd | Administrative & support | 2017 |