| Baldock Bespoke Ltd | Manufacturing | 2021 |
| Baldwin Design Consultancy Limited | Professional & scientific | 2007 |
| Balenfort Limited | Administrative & support | 2013 |
| Ball Media Ltd | Information & communication | 2023 |
| Ballard Aesthetics Limited | Other services | 2025 |
| Ballard Evans Corporate Finance Limited | Financial services | 2009 |
| Balloon Bouquet Bliss Co. Ltd. | Hospitality | 2023 |
| Balo Properties Ltd | Real estate | 2021 |
| Balsini Ltd | Wholesale & retail | 2020 |
| Balt Analytics Limited | Administrative & support | 2023 |
| Banbrace Limited | Wholesale & retail | 2019 |
| Bancon-It ASI Ltd | Information & communication | 2024 |
| Bandgrade Services Limited | Professional & scientific | 1988 |
| Bank Farm Grove Management Company Limited | Households | 2019 |
| Baoji Limited | Health & social care | 2020 |
| Bar Etna Limited | Hospitality | 2022 |
| Bar-Ba-Loot-Suit Limited | Professional & scientific | 2022 |
| Barakat Aviorepair Limited | Professional & scientific | 2026 |
| Barber's Bar Ltd | Other services | 2019 |
| Barbican Orthodontics Ltd | Health & social care | 2018 |
| Barchitect Solutions Limited | Information & communication | 2025 |
| Barclay Accounting Services Limited | Professional & scientific | 2019 |
| Barclay Blackthorn Legal Services Ltd | Professional & scientific | 2013 |
| Bard House Management Ltd | Real estate | 2019 |
| Bargains and Brands Ltd | Wholesale & retail | 2011 |
| Barinthus Biotherapeutics (UK) Limited | Professional & scientific | 2016 |
| Barinthus Biotherapeutics PLC | Financial services | 2021 |
| Bark Park Central Ltd | Other services | 2019 |
| Barlow House Management Company Limited | Households | 1990 |
| Barlow Stores Ltd | Wholesale & retail | 2023 |
| Barnell Properties Ltd | Real estate | 2025 |
| Barnes Walker Landscapes Ltd | Administrative & support | 2005 |
| Barnes Walker Limited | Administrative & support | 2001 |
| Barnsley Consulting Limited | Professional & scientific | 2023 |
| Barra Velha Limited | Professional & scientific | 2023 |
| Barrington Lodge Veterinary Clinic Limited | Professional & scientific | 2013 |
| Barringtoncooper Ltd | Financial services | 2009 |
| Barron Abodes Limited | Households | 2023 |
| Barrowcrete Limited | Construction | 2018 |
| Barry Bladon (Hale) Limited | Wholesale & retail | 1985 |
| Barry Hart Limited | Real estate | 2018 |
| Barry Hunt Windows Limited | Construction | 2006 |
| Barrymango Limited | Health & social care | 2024 |
| Bartimaeus Enterprising Solutions and Technologies Limited | Wholesale & retail | 2018 |
| Barton-Jones Consulting Services Ltd | Administrative & support | 2023 |
| BAS Estates Ltd | Real estate | 2023 |
| Base Reality Interactive Limited | Professional & scientific | 2026 |
| Base Skncare Ltd | Wholesale & retail | 2019 |
| Basilica Services Ltd | Information & communication | 2024 |
| Bass Angling Conservation Limited | Arts & recreation | 2023 |
| Batch Arms Limited | Hospitality | 2023 |
| Batch Bottlestore Limited | Hospitality | 2019 |
| Bath Property Company Limited | Real estate | 2003 |
| Bathbridge Consulting Limited | Professional & scientific | 2026 |
| Batta Ltd | Hospitality | 2019 |
| Battersea Park Court RTM Company Limited | Households | 2004 |
| Battlefield Holdings Ltd | Real estate | 2022 |
| Bauer Property Limited | Real estate | 2024 |
| Bauhaus Consultants Limited | Administrative & support | 2003 |
| Bavarian Nordic UK Ltd | Health & social care | 2024 |
| Bayfield Capital Limited | Real estate | 2006 |
| Baymews Limited | Professional & scientific | 1996 |
| BBS Switchgear Ltd | Construction | 2013 |
| Bbsai Solutions Limited | Professional & scientific | 2021 |
| BC Bidco 1 Holdings Ltd | Financial services | 2025 |
| BC Bidco 1 Ltd | Financial services | 2025 |
| BC Bidco 3 Ltd | Financial services | 2025 |
| BC Bidco 4 Limited | Financial services | 2025 |
| BC Bidco 5 Limited | Financial services | 2026 |
| BC Bidco 6 Limited | Financial services | 2026 |
| BC Holdco 5 Limited | Financial services | 2026 |
| BC Holdco 6 Limited | Financial services | 2026 |
| BCA Productions Limited | Information & communication | 1978 |
| BCF Investments Limited | Wholesale & retail | 2023 |
| BCL Holdings (NW) Ltd | Real estate | 2022 |
| Bcme Properties Ltd | Real estate | 2021 |
| BCS Cleaning Limited | Other services | 2014 |
| Bcsf Stamford Property SPV Ltd | Real estate | 2026 |
| Bcybersecure Limited | Information & communication | 2025 |
| BD Health Ltd | Health & social care | 2025 |
| Bdbb Limited | Financial services | 2025 |
| BDC Specialist Finance Ltd | Financial services | 2022 |
| BDG UK Ltd | Administrative & support | 2026 |
| BDS Eyecare Ltd | Wholesale & retail | 2021 |
| BE Electrical Services Ltd | Construction | 2020 |
| BE That Woman Ltd | Health & social care | 2024 |
| BE Trendy Ltd | Wholesale & retail | 2023 |
| Be-Baby Limited | Wholesale & retail | 2014 |
| Beach House Spirits Ltd | Manufacturing | 2022 |
| Beacon Consultancy Solutions Ltd | Health & social care | 2015 |
| Beain Ltd | Information & communication | 2024 |
| Beam UK Biggleswade Management Limited | Real estate | 2022 |
| Beanstalk Telecom Ltd | Information & communication | 2004 |
| Beanz Accounts Ltd | Professional & scientific | 2017 |
| Bear Mountain Ltd | Real estate | 2025 |
| Beards and Jackson Limited | Health & social care | 2014 |
| Beaufort Group Ltd | Real estate | 2023 |
| Beaupre Management Limited | Households | 1986 |
| Beauthorn House Limited | Real estate | 1972 |
| Beauty Trend UK Limited | Wholesale & retail | 2011 |