| Brazilarte Circle CIC | Arts & recreation | 2020 |
| Brazilarte Limited | Arts & recreation | 2012 |
| Breavington Properties LLP | | 2022 |
| Breese Ltd | Wholesale & retail | 2024 |
| Brelfin Limited | Real estate | 2017 |
| Brenbase Properties Limited | Real estate | 1997 |
| Brenford Properties Limited | Real estate | 2018 |
| Brentwood Central Management Company Limited | Real estate | 2023 |
| Breva Records Ltd | Information & communication | 2025 |
| Brickstock Furze Freehold Limited | Households | 2023 |
| Brickwork Quantity Surveying Services Ltd | Professional & scientific | 2025 |
| Bridge Start-Up Finance Limited | Professional & scientific | 2019 |
| Bridges & Sons GAS Ltd | Construction | 2023 |
| Briggs Air Limited | Construction | 2019 |
| Bright Horizon Cleaning Ltd | Administrative & support | 2023 |
| Bright Horizons Care Recruitment Limited | Health & social care | 2021 |
| Bright Payments Consultancy Limited | Professional & scientific | 2025 |
| Bright Spark Collective Ltd | Administrative & support | 2025 |
| Bright Spot International Limited | Professional & scientific | 2016 |
| Brisad Limited | Wholesale & retail | 2011 |
| Britannia Trading Corporation Ltd | Wholesale & retail | 2023 |
| Britcare Property Services Limited | Construction | 2024 |
| Britminds Limited | Professional & scientific | 2025 |
| Brmk Property Ltd | Real estate | 2024 |
| Broad Payne Limited | Construction | 2018 |
| Broad-Leaf Developments Limited | Construction | 2011 |
| Broadway Creek UK Limited | Financial services | 2024 |
| Broadway Movement LLP | | 2025 |
| Broadway Vanguard Supplies Limited | Construction | 1993 |
| Brockley Grove UK Limited | Financial services | 2024 |
| Brodie Business Centre Ltd | Administrative & support | 2019 |
| Bromley Engineering & Consultancy Limited | Construction | 2025 |
| Brook View (Blackburn) Management Company Limited | Households | 2015 |
| Brooke Trading Estate Limited | Households | 2009 |
| Brookprice Limited | Manufacturing | 1992 |
| Brookshield Healthcare Ltd | Health & social care | 2024 |
| Broomfield Utilities Ltd | Construction | 2022 |
| Brother LDN Limited | Wholesale & retail | 2026 |
| Browns Plumbing Ltd | Construction | 2008 |
| Brownstone Driveways Ltd | Administrative & support | 2022 |
| Broxhill Road Limited | Construction | 2019 |
| Brunel Computer Services Limited | Manufacturing | 1997 |
| Brunswick Business Services Limited | Professional & scientific | 2008 |
| Brunswick Heating Ltd | Construction | 2016 |
| Bryant Rigs Ltd | Construction | 2025 |
| Bryson Group Limited | Professional & scientific | 2023 |
| BT Convenience Ltd | Wholesale & retail | 2019 |
| BTS Crane Services Ltd | Construction | 2012 |
| Buckhurst Gate Residents Company Limited | Households | 2005 |
| Buddha Belly Southend Ltd | Hospitality | 2025 |
| Buddies Diner Ltd | Hospitality | 2021 |
| Buddy Box Films Limited | Information & communication | 2014 |
| Buddytutor Ltd | Education | 2022 |
| Budget CUT Limited | Construction | 2008 |
| Budleigh Doodles Ltd | Agriculture & fishing | 2020 |
| Budleigh Irish Doodles Ltd | Agriculture & fishing | 2021 |
| Buglem Limited | Hospitality | 2018 |
| Build Team Solutions Ltd | Construction | 2003 |
| Build-Trans Ltd | Construction | 2018 |
| Building Things Ltd | Information & communication | 2018 |
| Buildlever Innovations Limited | Information & communication | 2025 |
| Bull Creative Consultants Limited | Arts & recreation | 2015 |
| Bull Fanwear Limited | Wholesale & retail | 2026 |
| Bullmans Wharf Marine Limited | Financial services | 2022 |
| Bunch Healthcare Ltd | Administrative & support | 2025 |
| Bunker 19 Ltd | Arts & recreation | 2023 |
| Bunters Yard Limited | Wholesale & retail | 2025 |
| Burdaco Limited | Construction | 2025 |
| Burleigh Court RTM Company Limited | Households | 2014 |
| Burning Branch Ltd | Information & communication | 2004 |
| Burnt Mills Tyres Limited | Other services | 1993 |
| Bush Builders (Essex) Limited | Construction | 2024 |
| Bush Property Services Limited | Real estate | 2025 |
| Business Education Partnership South East Essex Limited | Education | 1997 |
| Business Efficiency Limited | Information & communication | 2006 |
| Busy Stitch Pro Limited | Manufacturing | 2026 |
| Butler Property Group Limited | Real estate | 2018 |
| Butler Solutions Ltd | Information & communication | 2012 |
| Buy 2 Rent Limited | Extraterritorial | 2010 |
| Buynew Holdings Ltd | Information & communication | 2025 |
| Buzz Box Limited | Wholesale & retail | 2001 |
| Bwoc Developments Limited | Construction | 2016 |
| BY Sydney Longmuir Limited | Other services | 2024 |
| Byfords Building Repairs Ltd | Other services | 2017 |
| Bytebraid Ltd | Information & communication | 2021 |
| C & B International Limited | Wholesale & retail | 2017 |
| C & L Automotive Bodyshop Ltd | Wholesale & retail | 2019 |
| C & S Grab Services Ltd | Administrative & support | 2017 |
| C & S Home Maintenance Services Ltd. | Water & waste | 2017 |
| C Carino Ltd | Health & social care | 2019 |
| C P Southern (Holdings) Limited | Financial services | 2011 |
| C Pond & Family Limited | Construction | 2020 |
| C Stevens Family Holdings Limited | Real estate | 2018 |
| C&C Collections Limited | Administrative & support | 2020 |
| C&C Property Group Ltd | Construction | 2022 |
| C&O's Vape Co. Limited | Wholesale & retail | 2016 |
| C&S Global Ltd | Manufacturing | 2022 |
| C&Speed Car Ltd | Wholesale & retail | 2014 |
| C&T Drinks Ltd | Hospitality | 2019 |
| C. Jones Construction Limited | Construction | 2012 |