| Blue Duck Education Ltd | Education | 2008 |
| Blue Flamingo Music Limited | Arts & recreation | 1988 |
| Blue INK Developments Limited | Real estate | 2017 |
| Blue Ridge Refurbs Limited | Real estate | 2024 |
| Blue Salmon Enterprises Limited | Arts & recreation | 2023 |
| Bluebird Essentials Ltd | Wholesale & retail | 2026 |
| Bluecoats Hertford (Alexandra House) RTM Company Limited | Households | 2024 |
| Blueyellowco Ltd | Professional & scientific | 2022 |
| BM Retailers PVT Ltd | Wholesale & retail | 2021 |
| BM Wheels and Tyres Ltd | Wholesale & retail | 2024 |
| Bo-Smart Ltd | Administrative & support | 2022 |
| BOB Deering Limited | Financial services | 2017 |
| BOB Solutions UK Ltd | Professional & scientific | 2023 |
| Bobb Management Limited | Real estate | 2022 |
| Bobby's Childcare Limited | Health & social care | 2017 |
| Bobby's Wheels and Tyres Limited | Wholesale & retail | 2018 |
| Body Health Group Ltd | Health & social care | 2020 |
| Boilerman (Herts) Limited | Construction | 2006 |
| Boilerpro Ltd | Construction | 2016 |
| Bongthai Ltd | Hospitality | 2017 |
| Bonn Events Limited | Professional & scientific | 2020 |
| Boogie Bear Music & Drama Limited | Education | 2017 |
| Bookbinders of London Limited | Information & communication | 1969 |
| Border in a Box Limited | Professional & scientific | 2011 |
| Borne Homes Limited | Real estate | 2007 |
| Borough Smart Limited | Information & communication | 2019 |
| Borough Smart Technology Limited | Information & communication | 2022 |
| Boston Digital Limited | Information & communication | 2016 |
| Both Barrels PUB Co. Ltd. | Hospitality | 2019 |
| Boudica Mousehold Limited | Real estate | 2018 |
| Boulivan IT Ltd | Information & communication | 2024 |
| Boundary Software Ltd | Information & communication | 2026 |
| Bourke Construction London Ltd | Construction | 2014 |
| Bourne Grove Limited | Real estate | 2014 |
| Box Cleaning London Ltd | Administrative & support | 2024 |
| BPM Contracts Services Ltd | Construction | 2024 |
| BPN Ventures Ltd | Information & communication | 2023 |
| Bracey’S Accountants (Hertford) Limited | Professional & scientific | 2022 |
| Bradley Mechanical Services Limited | Construction | 2024 |
| Brags London Limited | Hospitality | 2026 |
| Brakeons Ltd | Professional & scientific | 2023 |
| Bramfield Trading Company Ltd | Information & communication | 2025 |
| Brand IQ Limited | Manufacturing | 2017 |
| Brand IQ Technologies Ltd | Manufacturing | 2019 |
| Brand Seen Limited | Extraterritorial | 2012 |
| Brand Watches and Diamonds Limited | Extraterritorial | 2012 |
| Branue Limited | Information & communication | 2025 |
| Brass Trading Limited | Professional & scientific | 2000 |
| Bray C.E Ltd | Construction | 2026 |
| Brayford Properties Limited | Real estate | 2002 |
| Breeze Environmental Solutions Limited | Construction | 2015 |
| Breslin Public Policy Limited | Professional & scientific | 2010 |
| Brett Marshall Services UK Limited | Construction | 2017 |
| Brewbarn Beverage Innovations Global Ltd | Manufacturing | 2026 |
| Brickendon Grange Developments Limited | Construction | 2016 |
| Bricket Wood Auto Service & Repair Ltd | Wholesale & retail | 2021 |
| Brides Farm Livery Limited | Agriculture & fishing | 2024 |
| Bridge Court (Welwyn) Management Company Limited | Households | 2004 |
| Bridge Engineering & Transmission Limited | Professional & scientific | 2013 |
| Bridge Finance Direct Limited | Financial services | 2016 |
| Bridge Place (Bricket Wood) Management Company Limited | Households | 2007 |
| Bridge Road Welwyn Limited | Construction | 2018 |
| Bridgehart Limited | Administrative & support | 2025 |
| Bridget B'S Limited | Manufacturing | 2007 |
| Bridget Online 247 Limited | Information & communication | 2019 |
| Brigade Court Investco Limited | Real estate | 2019 |
| Brigade Court Management Limited | Real estate | 2019 |
| Brightlingsea K H Freehold Limited | Households | 2009 |
| Brinkley Grove (Two) Management Company Limited | Households | 2005 |
| Brinkley Scientific Limited | Professional & scientific | 2018 |
| Britannia Close (Northolt) Management Company Limited | Households | 1983 |
| British Motorsports Marshals' Club Limited | Other services | 1969 |
| Brixton Trade Services Ltd | Construction | 2025 |
| Brnup Solutions Limited | Information & communication | 2025 |
| Bro-Ken Ltd | Administrative & support | 2014 |
| Broad Oak Manor Developments Limited | Health & social care | 2001 |
| Broadmeads (Ware) Management Limited | Households | 1983 |
| Broadwater Electrical Ltd | Construction | 2021 |
| Broadwater Living Limited | Real estate | 2025 |
| Broadwood Site Services Ltd | Administrative & support | 2009 |
| Brocket Hall (UK) Limited | Arts & recreation | 2016 |
| Bromham Management Limited | Financial services | 2018 |
| Brookmans 4 Ltd | Real estate | 2019 |
| Brookmans Park Tree Surgery Ltd | Agriculture & fishing | 2018 |
| Brooks Quayle Global Resourcing Ltd | Administrative & support | 2012 |
| Brooksky Ltd | Real estate | 2014 |
| Brookson (5016E) Limited | Professional & scientific | 2007 |
| Brothers Tyres Ltd | Wholesale & retail | 2025 |
| Brown Dog Developments Limited | Construction | 2016 |
| Budget Headphones Limited | Education | 2020 |
| Build & Remodel Ltd | Construction | 2025 |
| Building and Construction Limited | Construction | 2019 |
| Building&Remodeling Limited | Construction | 2016 |
| Bull Point Capital Ltd | Professional & scientific | 2015 |
| Bulldog Tools (North America) Ltd | Wholesale & retail | 2017 |
| Bullrig Electrical Services Ltd | Construction | 2026 |
| Bunkworks Ltd | Information & communication | 2024 |
| Burleigh James Ltd | Administrative & support | 2013 |
| Business and Skills Support Ltd | Professional & scientific | 2017 |
| Business Environment Basingstoke Limited | Administrative & support | 2006 |