| Biodigester Products Ltd | Manufacturing | 2008 |
| Biofare Investments Limited | Manufacturing | 2011 |
| Bionex Ltd | Financial services | 2020 |
| Biosynth Group Limited | Financial services | 2021 |
| Biosynth Laboratories Limited | Manufacturing | 1999 |
| Biosynth Limited | Manufacturing | 2006 |
| Biotrend Ltd | Wholesale & retail | 2015 |
| Biowatt Facilities Management Limited | Construction | 2016 |
| Biowatt Site Services Limited | Construction | 2015 |
| Biquet Ltd | Other services | 2016 |
| Birchwood Consulting Limited | Professional & scientific | 2026 |
| Bishops Green Farm Limited | Agriculture & fishing | 2017 |
| Bite Express Ltd | Hospitality | 2022 |
| Bitech Data Limited | Information & communication | 2005 |
| Bitech Digital Limited | Information & communication | 2011 |
| Bitek Software Ltd | Information & communication | 2016 |
| Biys Corporation Limited | Information & communication | 2025 |
| Bizznet.Uk Ltd | Administrative & support | 2010 |
| BJT Mechanical Solutions Limited | Construction | 2017 |
| Black Bear Honey Company Ltd | Manufacturing | 2020 |
| Black Bear Ltd | Manufacturing | 2021 |
| Black Rainbow Consulting Limited | Professional & scientific | 2017 |
| Black Rock SKI Lodge Limited | Hospitality | 2012 |
| Blackthorn Hudson Group Ltd | Financial services | 2026 |
| Blackthorn Hudson Limited | Transport & logistics | 2026 |
| Blackthorne EOT Limited | Professional & scientific | 2024 |
| Blackthorne International Transport Ltd | Transport & logistics | 2009 |
| Bladon Investments Ltd | Other services | 2021 |
| Blake Consult Ltd | Professional & scientific | 2023 |
| Blakes Building Profiles Limited | Manufacturing | 1988 |
| Blankcanvaspropertysolutions Limited | Real estate | 2021 |
| Blenix Chain Technology Ltd | Information & communication | 2025 |
| Blesovsky Limited | Other services | 2015 |
| Blewbury Down Mews (Compton) Management Company Limited | Households | 2005 |
| Blindspot Enterprises Limited | Real estate | 2014 |
| Blink Creative Limited | Manufacturing | 2001 |
| BLISS5 Consulting Limited | Information & communication | 2016 |
| Block 5 Wentworth Court (Freehold) Limited | Real estate | 2016 |
| Block Management Specialists (Thames Valley) Limited | Real estate | 2014 |
| BLS (UK Holdings) Limited | Financial services | 2020 |
| BLS (UK) Limited | Financial services | 2000 |
| BLS Solutions Ltd | Information & communication | 2025 |
| Blue Aspire LLP | | 2008 |
| Blue Box Events Ltd | Wholesale & retail | 2023 |
| Blue Helix Limited | Extraterritorial | 2003 |
| Blue Lemon Training Limited | Professional & scientific | 2016 |
| Blue Tortoise Limited | Administrative & support | 2014 |
| Blue Truffle Ltd | Administrative & support | 2015 |
| Blue Van Builders Limited | Other services | 2023 |
| BLUE2GREEN Limited | Professional & scientific | 2014 |
| Bluecore Heating & Plumbing Services Limited | Construction | 2023 |
| Bluegreen Magic IT Consultancy Limited | Information & communication | 2022 |
| Bluewave Finance Solutions Limited | Professional & scientific | 2023 |
| Blyth Wealth Management Limited | Professional & scientific | 2020 |
| BMG Consulting Ltd | Professional & scientific | 2019 |
| BMG Prestige Ltd | Manufacturing | 2026 |
| Boardman Developments Limited | Construction | 2016 |
| BOB Brewer Limited | Construction | 2008 |
| BOB Cady Services Ltd | Professional & scientific | 2010 |
| BOD -Nant Estates Limited | Real estate | 1962 |
| Bodex Building Services Ltd | Construction | 2019 |
| Body Bonito Limited | Other services | 2024 |
| Boiler Spares 2 Go Limited | Extraterritorial | 2014 |
| Bollinger Bertie Limited | Real estate | 2019 |
| Bond Woodhouse Limited | Professional & scientific | 2000 |
| Bonsai Marketing & Management Services Limited | Professional & scientific | 1994 |
| Bonzai Communications Limited | Administrative & support | 2014 |
| Boogie Pumps Newbury Ltd | Arts & recreation | 2026 |
| Booktastic Newbury CIC | Education | 2026 |
| Boomerang Nutrition Limited | Administrative & support | 2015 |
| Boori (Europe) Limited | Administrative & support | 2005 |
| Bose Solutions Limited | Information & communication | 2025 |
| Botanic Project & Maintenance (UK) Ltd | Arts & recreation | 2023 |
| Boulter Tippers Limited | Manufacturing | 1983 |
| Boundary Road Estates Limited | Real estate | 2025 |
| Boundless Films Ltd | Information & communication | 2019 |
| Bournebridge Golf Club Limited | Arts & recreation | 1962 |
| Box 1 Andover Ltd | Real estate | 2026 |
| Boxford Masques | Arts & recreation | 2003 |
| Bpac Consulting Limited | Professional & scientific | 2017 |
| Bpac Property Investments Limited | Real estate | 2019 |
| BPC Property Limited | Real estate | 2017 |
| Braces (Holdings) Ltd | Financial services | 2021 |
| Bradfield Investment Company Limited | Extraterritorial | 2008 |
| Bradfield Properties Limited | Real estate | 2000 |
| Brading Cryer Limited | Professional & scientific | 2001 |
| Bradmill Meat Limited | Manufacturing | 1980 |
| Bramleigh Advisory Limited | Professional & scientific | 2026 |
| Brandmasters Limited | Other services | 2000 |
| Bravo Hairdressing Limited | Other services | 2003 |
| Breakthrough Minds Limited | Administrative & support | 2021 |
| Breathing Arts Ltd | Information & communication | 2021 |
| Breathing in Peace C.I.C. | Other services | 2019 |
| Bremad Ltd | Real estate | 2015 |
| Brian Gubby Limited | Wholesale & retail | 1979 |
| Brickman Actuarial Services Ltd | Professional & scientific | 2018 |
| Brickman Property Services Ltd | Real estate | 2020 |
| Brickman Souter Properties Limited | Real estate | 2022 |
| Bricks and Mortar Surveys (Wessex) Limited | Professional & scientific | 2025 |
| Bridgemere 19 Limited | Extraterritorial | 2022 |