| Betty Cassie Django Limited | Wholesale & retail | 2026 |
| BFS Farm Services Limited | Financial services | 2020 |
| BGS Education Ltd | Education | 2018 |
| Big Boots Theatre Company Limited | Arts & recreation | 2016 |
| Big Boss Warehouse Ltd | Wholesale & retail | 2024 |
| Bill's Mobile Tyres Wickford Ltd | Extraterritorial | 2023 |
| Billericay Bathroom Design Limited | Other services | 2013 |
| Billericay Building Ltd | Construction | 2016 |
| Billericay Storage Ltd | Transport & logistics | 2015 |
| Billericay Supporters Group Limited | Arts & recreation | 2019 |
| Biosystems Event Productions Limited | Arts & recreation | 2020 |
| Bite and CUT Resistant Clothing Limited | Wholesale & retail | 2022 |
| Bitwise-It Limited | Information & communication | 2009 |
| Bizturbo Ltd | Professional & scientific | 2023 |
| BJE Building Limited | Construction | 2018 |
| Bksk Properties Limited | Construction | 2022 |
| BKW Contractors Limited | Construction | 2013 |
| Black Opal the Fitted Furniture Company Limited | Manufacturing | 2020 |
| Black Orchid Events Ltd | Hospitality | 2022 |
| Blake Air Conditioning Ltd | Construction | 2009 |
| Blakes Contractors Limited | Construction | 2021 |
| Blast N Coat Limited | Manufacturing | 2024 |
| Bleu Property Management Ltd | Construction | 2017 |
| Bling IT on Occasions Ltd | Administrative & support | 2019 |
| BLL Tankers Ltd | Water & waste | 2021 |
| Blockdebt Limited | Administrative & support | 2023 |
| Blondies Bakes Ltd | Manufacturing | 2021 |
| Blossom Hill Florist Ltd | Wholesale & retail | 2022 |
| Blou Construction Limited | Construction | 2010 |
| Blou Dynamic Limited | Construction | 2022 |
| BLU Accounting Limited | Professional & scientific | 2018 |
| Blue Horizon Innovation Limited | Manufacturing | 2020 |
| Blue Ocean Independent Financial Planning Ltd | Financial services | 2019 |
| Bluearch Investment Ltd | Financial services | 2026 |
| Bluebaring Resources Ltd | Administrative & support | 2019 |
| Bluedog Business Solutions Ltd | Administrative & support | 2020 |
| Bluedovemedia Limited | Professional & scientific | 2019 |
| Bluegate Holdings Ltd | Administrative & support | 2026 |
| Blueprint Estate Agents Luton Limited | Real estate | 2018 |
| Blueprint Estates (London) Limited | Real estate | 2019 |
| Blueprint Lettings and Management Ltd | Real estate | 2016 |
| Blueprint Property Group Limited | Extraterritorial | 2019 |
| Blxio Limited | Financial services | 2025 |
| BMD Estates Limited | Real estate | 2015 |
| BML Properties & Developments Limited | Real estate | 2018 |
| BO$$ Barber Ltd | Other services | 2020 |
| BOA Training Ltd | Education | 2021 |
| Bodytech Repair Solutions Limited | Wholesale & retail | 2016 |
| Boiler Recycling Ltd | Other services | 2016 |
| Bonphoto Limited | Professional & scientific | 2002 |
| Bonville Facilities Ltd | Real estate | 2017 |
| Bordeaux Packaging Ltd | Administrative & support | 2015 |
| Bornwest Limited | | 1978 |
| Borrowdale Construction Homes Limited | Construction | 2008 |
| Borrowdale Construction Limited | Real estate | 1984 |
| Borsea Corporation Limited | Construction | 1996 |
| Bosy Ceilings Limited | Construction | 2021 |
| Bouer Ltd | Construction | 2023 |
| Bowers Haulage Limited | Transport & logistics | 2026 |
| Box Valley Property Limited | Construction | 2021 |
| Boxer Building and Landscaping Limited | Administrative & support | 2013 |
| Boxer Media Limited | Other services | 2010 |
| Boyd's Home and Garden Ltd | Wholesale & retail | 2013 |
| BPR Engineering Ltd | Professional & scientific | 2011 |
| BPW Painting & Decorating Ltd | Construction | 2026 |
| BR Healthcare Limited | Health & social care | 2022 |
| Bradgate Developments (Wickford) Limited | Construction | 2004 |
| Bradgate Developments (Wickford) Phase 2 Limited | Professional & scientific | 2004 |
| Brads Bulldog Enterprise Ltd | Manufacturing | 2014 |
| Braiden Plumbing & Heating Limited | Construction | 2016 |
| Brainbox Candy Limited | Professional & scientific | 2008 |
| Bramley White Developments Ltd | Construction | 2025 |
| Brandlabx Limited | Wholesale & retail | 2025 |
| Brandon Brothers Company Ltd | Construction | 2023 |
| Brass Oak Limited | Construction | 2020 |
| Brave Steel Ltd | Construction | 2019 |
| Braven Limited | Real estate | 2024 |
| Braybrook Rail Ltd | Construction | 2022 |
| Brayway Limited | Real estate | 2001 |
| Breaded Streamers Ltd | Professional & scientific | 2025 |
| Breakthestigmauk (Btsuk) C.I.C. | Administrative & support | 2021 |
| Brennan Hvac Technical FM Ltd | Construction | 2026 |
| Brennan Plumbing and Heating Services Ltd | Construction | 2023 |
| Brentwood and District Crossroads Care Attendant Scheme | Health & social care | 1996 |
| Brett Heasman Roofing Ltd | Construction | 2020 |
| BREW81 Limited | Hospitality | 2022 |
| Bridge Education (AP) Limited | Education | 2020 |
| Briffa Consultancy Ltd | Professional & scientific | 2022 |
| Bright Sparky Ltd | Construction | 2011 |
| Bright Starts Childcare Group Limited | Health & social care | 2021 |
| Brighter Builders Ltd | Construction | 2020 |
| Brighter Leaders Limited | Education | 2024 |
| Brindell Limited | Administrative & support | 2014 |
| Brinson House RTM Company Ltd | Households | 2020 |
| Brit I Group Ltd | Financial services | 2020 |
| Britain Israel Communications & Research Centre | Information & communication | 2001 |
| Britannia Capital Properties Ltd | Real estate | 2026 |
| Britannia Data Limited | Information & communication | 1998 |
| Briton House Properties Limited | Real estate | 1989 |
| Broadcast PR Ltd | Professional & scientific | 2018 |