| BOO BLG Limited | Financial services | 2003 |
| Book Curl Ltd | Wholesale & retail | 2023 |
| Bookham Chartered Physiotherapy Service Ltd | Health & social care | 2003 |
| Booksmart Consultancy Ltd | Professional & scientific | 2013 |
| Boom! Global Limited | Administrative & support | 2019 |
| Boomerang Barber Shop Limited | Real estate | 2008 |
| Boost Broadcast Ltd | Information & communication | 2023 |
| Booth Fencing Limited | Construction | 2015 |
| Borde Hill Energy Limited | Other services | 2015 |
| Borde Hill Events Limited | Agriculture & fishing | 1991 |
| Borde Hill Garden Limited | Arts & recreation | 1965 |
| Borde Hill Hospitality LLP | | 2022 |
| Boretec Construction Limited | Construction | 2020 |
| Bosun Mechanical Services Ltd | Manufacturing | 2021 |
| Boswell Property Services (Sussex) Ltd | Real estate | 2022 |
| Bottega Veneta U.K. Co. Limited | Wholesale & retail | 1994 |
| Boucheron (UK) Limited | Wholesale & retail | 1936 |
| Boudicca IT Limited | Information & communication | 2016 |
| Boulder Engineering Limited | Manufacturing | 2009 |
| Bowalker Windows Ltd | Wholesale & retail | 2009 |
| Bowens Kennels LLP | | 2005 |
| Bowley & Gallagher Limited | Other services | 1997 |
| Box 2 Ltd | Wholesale & retail | 1992 |
| Boyles Properties Ltd | Real estate | 2023 |
| BPM Dance Academy Limited | Arts & recreation | 2011 |
| BPM Workshops Limited | Other services | 2015 |
| Brainiac Media Limited | Information & communication | 2012 |
| Brainwave (Services) Limited | Health & social care | 2014 |
| Bramble Place Management Company Limited | Households | 2026 |
| Branagan Coaching and Consultancy Limited | Professional & scientific | 2025 |
| Brand & Boost Limited | Information & communication | 2021 |
| Brand Borne Limited | Information & communication | 2016 |
| Brand Champion Bootcamp Limited | Education | 2022 |
| Brass Trustees Limited | Professional & scientific | 2020 |
| Breen Equestrian Limited | Other services | 2007 |
| Breeze Photo Ltd | Professional & scientific | 2022 |
| Brett Norris Fire Training Ltd | Professional & scientific | 2018 |
| Brett Tyres Limited | Wholesale & retail | 2018 |
| Brewbrands Limited | Administrative & support | 2011 |
| Bribourne Limited | Professional & scientific | 1970 |
| Bricks & Beyond Limited | Real estate | 2020 |
| Bricks & Daughter Limited | Real estate | 2007 |
| BRID9E Limited | Other services | 2025 |
| Bridge and BUN Ltd | Hospitality | 2026 |
| Bridge Hall Golf Limited | Arts & recreation | 1995 |
| Bridge Place Limited | Real estate | 2021 |
| Bridgefield Trading Ltd | Wholesale & retail | 2015 |
| Bridgeham Clinic Ltd | Health & social care | 2003 |
| Bridgewater Accountants Ltd | Professional & scientific | 2019 |
| Briganti Films Ltd | Information & communication | 2026 |
| Bright Behaviour Solutions Ltd | Professional & scientific | 2023 |
| Bright Care Recruitment Ltd | Administrative & support | 2020 |
| Bright Clean Services Ltd | Administrative & support | 2014 |
| Brightbridge Performance Limited | Professional & scientific | 2025 |
| Brighton Analytics Limited | Information & communication | 2021 |
| Brighton and Hove Sea Serpents Rugby Football Club Limited | Arts & recreation | 2024 |
| Brighton Early Music Festival Limited | Education | 2003 |
| Brighton Pianos Limited | Wholesale & retail | 2016 |
| Brightstove Limited | Professional & scientific | 1998 |
| Brioni UK Limited | Wholesale & retail | 2002 |
| Britannia Developments (South East) Limited | Real estate | 2004 |
| British Parking Association(The) | Professional & scientific | 1970 |
| Brixter Developments Ltd | Construction | 2022 |
| Brkd Limited | Wholesale & retail | 2021 |
| Broad Oak Tree Consultants Limited | Agriculture & fishing | 2004 |
| Broadway Heights Limited | Real estate | 2017 |
| BROADWAY44 Ltd | Hospitality | 2006 |
| Brompton Grove Limited | Construction | 2018 |
| Brook Lane Properties Ltd | Real estate | 2021 |
| Brooke and Associates Ltd | Professional & scientific | 2016 |
| Brooks Braithwaite (Sussex) Limited | Financial services | 1979 |
| Brookwood Plumbing and Heating Limited | Construction | 2020 |
| Browns Garage (Haywards Heath) Limited | Wholesale & retail | 1970 |
| Broxmead Biomass LLP | | 2013 |
| BRT Consulting Limited | Administrative & support | 2021 |
| Bruce Copen Laboratories Limited | Manufacturing | 1996 |
| Bruce Rayner Property Limited | Professional & scientific | 2014 |
| Brumsen Consulting Limited | Professional & scientific | 2010 |
| BSE Controls Limited | Manufacturing | 2024 |
| BSE3D Limited | Professional & scientific | 2011 |
| Bsefm Limited | Manufacturing | 2018 |
| BSW Energy Solutions Limited | Construction | 2010 |
| BSW Property Holdings Ltd | Real estate | 2024 |
| BTH Consulting Ltd | Professional & scientific | 2021 |
| BTI Consulting Ltd | Extraterritorial | 2021 |
| Buchan RUM Architects Limited | Professional & scientific | 2018 |
| Buck Real Estate Limited | Real estate | 2014 |
| Buckeridge Limited | Professional & scientific | 2022 |
| Buffalo Residential Investments LLP | | 2009 |
| Buffalo SY Limited | Hospitality | 2024 |
| BUG Hunter Limited | Information & communication | 2010 |
| Buildconsult International Ltd | Professional & scientific | 1999 |
| Building Blocks SLT Ltd | Health & social care | 2023 |
| Buildwise Construction (Sussex) Limited | Construction | 2007 |
| Bulstrode Farm Limited | Agriculture & fishing | 1942 |
| BUREAU543 Ltd | Professional & scientific | 2014 |
| Burgess Hill Youth | Arts & recreation | 2012 |
| Burhill Management Limited | Real estate | 2019 |
| Burn Stewart (Marylebone) Limited | Professional & scientific | 1973 |
| Burn Stewart (Sutton) Limited | Professional & scientific | 1947 |