| Brambleton Homes (Nately Scures) Ltd | Construction | 2025 |
| Bramdean Developments Ltd | Construction | 2007 |
| Bramley PUB Co Ltd | Hospitality | 2026 |
| Bramley Sales Consultants Limited | Professional & scientific | 2016 |
| Bramley Village Bakery Limited | Wholesale & retail | 2001 |
| Brampton (Southampton) Residents Association Limited | Households | 1963 |
| Brampton Manor (Southampton) Residents Association Limited | Households | 1962 |
| Branch 16 Limited | Information & communication | 2016 |
| Brand 81 Limited | Information & communication | 2015 |
| Brand Embassy Ltd | Information & communication | 2011 |
| Brand Rochester Ltd | Wholesale & retail | 2025 |
| Brandcare Group Limited | Wholesale & retail | 2008 |
| Branded Kitchens Ltd | Hospitality | 2025 |
| Brandenn Media Ltd | Information & communication | 2016 |
| Branding Worx Limited | Wholesale & retail | 2011 |
| Brandlydrop Ltd | Wholesale & retail | 2025 |
| Brandology Limited | Administrative & support | 2015 |
| Brandz Engage Ltd | Wholesale & retail | 2021 |
| Brantons LLP | | 2006 |
| Brass Knockers Ltd | Real estate | 2016 |
| Bravertinax, UK Ltd | Wholesale & retail | 2026 |
| Bravion Capital Limited | Financial services | 2025 |
| Brazier Systems and Consultants Limited | Extraterritorial | 1986 |
| Brazilian Churros Gourmet Ltd | Hospitality | 2025 |
| Brazuka Delivers Ltd | Transport & logistics | 2021 |
| Bread & Barrel Ltd | Construction | 2026 |
| Bread and Barrel Group Ltd | Hospitality | 2026 |
| Break-For-Life CIC | Arts & recreation | 2024 |
| Breakbeat Brewing Limited | Manufacturing | 2022 |
| Breakfast and Beyond Winchester Limited | Health & social care | 2025 |
| Breakout Youth | Health & social care | 2018 |
| Breakthrough Public Speaking Limited | Administrative & support | 2025 |
| BREAKTHRU4LIFFE Ltd | Other services | 2019 |
| Breaktime Coffee and Vending Limited | Wholesale & retail | 2023 |
| Breathe and Recover Limited | Professional & scientific | 2020 |
| Breathe Fundraising Ltd | Other services | 2017 |
| Breathlab Limited | Education | 2023 |
| Breckenridge & Viana Limited | Professional & scientific | 1982 |
| Breeze Builders Limited | | 1988 |
| Breeze Medical Invoicing Ltd | Health & social care | 2020 |
| Breeze People Ltd | Professional & scientific | 2010 |
| Breeze Removals Ltd | Transport & logistics | 2025 |
| Brekhna's Takeaway Ltd | Hospitality | 2023 |
| Bremaco Ltd | Manufacturing | 2022 |
| Bren Choice Ltd | Professional & scientific | 2009 |
| Brenchley Supplies Limited | Wholesale & retail | 2011 |
| Brenchleys Ltd | Wholesale & retail | 2011 |
| Brenden’S Bargains Ltd | Wholesale & retail | 2022 |
| Brenhaul Commercial Services Limited | Wholesale & retail | 1998 |
| Brenmar Ltd | Construction | 2018 |
| Brennan Plumbing & Heating Limited | Construction | 2007 |
| Brennan Property Services Limited | Real estate | 2015 |
| Brentwood Associates Limited | Professional & scientific | 2010 |
| Brentwood Business Services Limited | Administrative & support | 2021 |
| Brestive Ukeig | | 2011 |
| Brevity Yachting Limited | Arts & recreation | 2009 |
| Brewer Engineering Ltd | Manufacturing | 2024 |
| BRH Consulting Limited | Professional & scientific | 2020 |
| BRH Services Ltd | Construction | 2024 |
| Brhl Limited | Professional & scientific | 2008 |
| Brian Bouch Limited | Transport & logistics | 2002 |
| Brian Mcmonnies Ltd | Professional & scientific | 2014 |
| Briant Building Ltd. | Construction | 2003 |
| Briar Consulting Engineers Limited | Professional & scientific | 2017 |
| Briar Holdings Limited | Professional & scientific | 2017 |
| Briarswood Estates Ltd | Households | 2024 |
| Briarswood Management Limited | Households | 1992 |
| Brica IT 2023 Limited | Information & communication | 2022 |
| Brick Central Ltd | Wholesale & retail | 2024 |
| Brickhill Electrical Services Limited | Construction | 2016 |
| Brickland Building Developments Ltd | Construction | 2004 |
| Brickmakers (Brierley Hill) Ltd | Hospitality | 2024 |
| Brides of Southampton EST 1976 Limited | Administrative & support | 2017 |
| Bridge Education Trust (Southampton) | Education | 2023 |
| Bridge Gallery Limited | Wholesale & retail | 2002 |
| Bridge Road Sandweetch’S Ltd | Hospitality | 2025 |
| Bridge Rubber & Plastics Limited | Wholesale & retail | 2005 |
| Bridge Security Limited | Administrative & support | 2001 |
| Bridge Street House Limited | Hospitality | 2019 |
| Bridgeroad Group Ltd | Construction | 2017 |
| Bridgerton.Uk Ltd | Wholesale & retail | 2022 |
| Bridges Healthcare & Nursing Limited | Health & social care | 2004 |
| Bridgeway Connect Ltd | Information & communication | 2025 |
| Bridgeways ADR Ltd | Professional & scientific | 2025 |
| Bridgeworks Plus Ltd | Information & communication | 2023 |
| Bridgwater Court Management (Southampton) Limited | Households | 1996 |
| Bridport Court RTM Limited | Households | 2004 |
| Briel Design Limited | Professional & scientific | 2019 |
| Brig Construction Ltd | Construction | 2023 |
| Bright Blue Sky Heating Limited | Wholesale & retail | 2025 |
| Bright Electrical Ltd | Energy | 2014 |
| Bright Eyes Southern Ltd | Health & social care | 2012 |
| Bright Future Recruitment Solutions Ltd | Administrative & support | 2024 |
| Bright Haven Shop Ltd | Wholesale & retail | 2025 |
| Bright Invest Limited | Real estate | 2017 |
| Bright Lights Contractors Ltd | Other services | 2021 |
| Bright Moon Training, Coaching and Consultancy Limited | Education | 2023 |
| Bright QA Systems Ltd. | Construction | 1994 |
| Bright Spark Tuition Limited | Education | 2012 |
| Brightconsult Limited | Professional & scientific | 2009 |