| Bonians Limited | Wholesale & retail | 2001 |
| Bonney Brickwork Limited | Construction | 2025 |
| Boost Corporate Performance Limited | Professional & scientific | 2003 |
| Booth & Booth Ltd | Professional & scientific | 2010 |
| Booyah UK Limited | Professional & scientific | 2004 |
| Border Heating Services Ltd | Energy | 2018 |
| Borg Ventures Limited | Professional & scientific | 2001 |
| Bornerra Foods UK Limited Limited | Hospitality | 2025 |
| Borough Limited | Manufacturing | 1989 |
| Bos.Cltv Limited | Wholesale & retail | 2024 |
| Boss Air Limited | Transport & logistics | 2000 |
| Botanicals & Between Limited | Wholesale & retail | 2025 |
| Botec Ltd | Construction | 2026 |
| Bottle & Basket 2 Ltd | Wholesale & retail | 2004 |
| Bourne Bridge Nurseries Limited | | 1975 |
| Bowgen Limited | Professional & scientific | 2006 |
| Boww Ltd | Professional & scientific | 2026 |
| Boxfixdesign Ltd | Professional & scientific | 2026 |
| Boyce Hill Golf and Country Club Limited | Arts & recreation | 1922 |
| Boyd Autos Limited | Wholesale & retail | 2002 |
| Boyraci Fish and Chips Ltd | Hospitality | 2026 |
| BPC Interiors Trustee Limited | Professional & scientific | 2024 |
| Bpfc Limited | Health & social care | 2021 |
| Brad Global Cargo Limited | Other services | 2010 |
| Bradford Street Flats (Braintree) Limited | Households | 1992 |
| Bradford Watts Limited | Construction | 1984 |
| Bradgate View Homes Ltd | Real estate | 2026 |
| Bradleigh Building Contractors Ltd | Construction | 2002 |
| Bradshaw Fine Wood Furniture Limited | Manufacturing | 2004 |
| Bradwell Wholesale Ltd | Wholesale & retail | 2025 |
| Braintree Motor Company Limited | Wholesale & retail | 1998 |
| Brainxone Technologies Limited | Information & communication | 2026 |
| Braiswick Service Station Ltd. | Extraterritorial | 1998 |
| Brampton Consulting Ltd | Professional & scientific | 2001 |
| Bramwell & Lloyd Limited | Agriculture & fishing | 1952 |
| Branchin OUT Limited | Administrative & support | 2004 |
| Branching Tree Ventures Ltd | Wholesale & retail | 2025 |
| Branchsound Limited | Manufacturing | 1982 |
| Brand Research and Development LLP | | 2005 |
| Brand Scaler Ltd | Information & communication | 2026 |
| Brandcript Ltd | Administrative & support | 2026 |
| Brandflix Limited | Professional & scientific | 2023 |
| Brandlett Ltd | Wholesale & retail | 2025 |
| Brandora Media Ltd | Information & communication | 2026 |
| Brandora Studio Limited | Professional & scientific | 2025 |
| Branksome Building Services Limited | Construction | 1997 |
| Branoc Engineering Limited | Construction | 1996 |
| Bravo MR Ashcroft Ltd | Administrative & support | 2013 |
| Braybrook Limited | Construction | 2000 |
| Braybrook Services Limited | Manufacturing | 1997 |
| Breakway Properties Limited | Real estate | 1989 |
| Breast and Body Clinic Ltd | Health & social care | 2025 |
| Breezie Designs Limited | Information & communication | 1998 |
| Brents Financial Services Limited | Financial services | 1984 |
| Brents of Brentwood (Financial Services) Limited | Financial services | 1989 |
| Brentwood Kitchen Centre Limited | | 1967 |
| Brentwood Park Karting Centre Limited | Arts & recreation | 1996 |
| Brentwood Park SKI and Snowboard Centre Limited | Administrative & support | 2000 |
| Brentwood Specsavers Limited | Wholesale & retail | 1993 |
| Brentwood Theatre Trust | Arts & recreation | 1982 |
| Brettvale Golf Club Limited | Arts & recreation | 1990 |
| Brewery Lane (Coburn Estate) Management Company Limited | Households | 1974 |
| Bri-Chez Limited | Water & waste | 2007 |
| Brian Andrews Builders Limited | | 1985 |
| Brian Birt Carpets Limited | Wholesale & retail | 2003 |
| Brian Sheridan Cars (Hounslow) Limited | | 1987 |
| Briarcote Limited | Real estate | 1973 |
| Brick House Crafts Limited | Wholesale & retail | 2005 |
| Bridge Roofing Limited | Construction | 1997 |
| Bridge Street Estates Limited | Information & communication | 1968 |
| Bridgebank Homes Limited | Construction | 2016 |
| Bridged Gaps Film and Theatre Limited | Professional & scientific | 2025 |
| Bridgerent Limited | Real estate | 2025 |
| Bridgerent Property Management Limited | Real estate | 2025 |
| Bridgeview Court Management Company Limited(The) | Real estate | 1980 |
| Bright Delight Cleaners Ltd | Administrative & support | 2026 |
| Bright Investment Group Ltd | Real estate | 2021 |
| Brighthub Training & Recruitment Ltd | Education | 2024 |
| Brightkey Estate Ltd | Real estate | 2025 |
| Brightpath Retail Ltd | Wholesale & retail | 2026 |
| Brightsprings Group Limited | Wholesale & retail | 2011 |
| Brilanka Limited | Wholesale & retail | 1978 |
| Brilliant Minds Focus Jeweller Ltd | Manufacturing | 2025 |
| Brindlewyck Limited | Wholesale & retail | 2025 |
| Brit Select Ltd | Wholesale & retail | 2025 |
| Britailabs Ltd | Information & communication | 2025 |
| Britannia Mart Direct Ltd | Wholesale & retail | 2025 |
| Britannia Roofing & Construction Limited | Construction | 1999 |
| Britannia Sealants Limited | Construction | 2005 |
| Britannia Service Station Ltd | Wholesale & retail | 2004 |
| Britcrown Limited | Real estate | 1999 |
| Britishjobs.Net Limited | Professional & scientific | 2001 |
| Britluxe Cart Limited | Wholesale & retail | 2025 |
| Britova Developments Ltd | Construction | 2021 |
| Broach Limited | Real estate | 2007 |
| Broad Properties (Grays) Ltd | Real estate | 2020 |
| Broad Reach Partnership Limited | Professional & scientific | 1999 |
| Broadway Brothers Limited | Hospitality | 1955 |
| Bronze Trading Limited | Hospitality | 2019 |
| Bronzecourt Limited | | 1977 |