| Boom Lifts Ltd | Administrative & support | 2024 |
| Boom Pro Clean Ltd | Administrative & support | 2025 |
| Boons Social Limited | Professional & scientific | 2025 |
| Boops Place Ltd | Hospitality | 2026 |
| Boot LED Zeppelin Ltd | Arts & recreation | 2006 |
| Booth & Co Builders Ltd | Construction | 2014 |
| Booth & SON Limited | Manufacturing | 2005 |
| Boothfairy Partnership Ltd | Other services | 2023 |
| Boppers Limited | Wholesale & retail | 2002 |
| Bori Trans Ltd | Transport & logistics | 2025 |
| Boric Real Estate Limited | Real estate | 2005 |
| Borisfen Aviation Ltd | Professional & scientific | 2022 |
| Boristan Limited | Financial services | 2025 |
| Born to BEE Happy Ltd | Education | 2020 |
| Born to FLY Limited | Professional & scientific | 2018 |
| Borough News Limited | Real estate | 1985 |
| Borygo Limited | Transport & logistics | 2012 |
| Bosco Tree Management Limited | Agriculture & fishing | 2026 |
| Bose Consultants Limited | Professional & scientific | 2023 |
| Boss Empire Barber Ltd | Other services | 2026 |
| Boss MEN Ltd | Other services | 2020 |
| Botha Construction Consultancy Limited | Administrative & support | 2014 |
| Bouf's Hair & Beauty Ltd | Other services | 2018 |
| Boundary Property Management Ltd | Households | 2019 |
| Boundary Scaffolding Contractors Ltd | Construction | 2021 |
| Boundary Scaffolding Limited | Construction | 1997 |
| Bourdanne Photography Limited | Professional & scientific | 2020 |
| Bourton Avenue Limited | Professional & scientific | 2013 |
| Bourton Best Kebab Ltd | Hospitality | 2019 |
| Bourton Brickworks Limited | Construction | 2015 |
| BOV Logistics Company Ltd | Transport & logistics | 2026 |
| Bower Mapson Homes Limited | Construction | 2015 |
| Boweringjames Ltd | Professional & scientific | 2018 |
| Box Art Studios Ltd | Information & communication | 2017 |
| Box of Motola Ltd | Professional & scientific | 2013 |
| Box-N-X Ltd | Wholesale & retail | 2021 |
| Boxing Predicos Ltd | Information & communication | 2026 |
| Boxpilot Ltd | Transport & logistics | 2025 |
| Boxpilot Vehicle Hire Ltd | Administrative & support | 2026 |
| Boyce Groundworks Ltd | Construction | 2023 |
| Boyes Air Conditioning Ltd | Construction | 2024 |
| Bozovali & Co Ltd | Other services | 2023 |
| Bp&H Ltd | Construction | 2024 |
| Bp.Gurkha Foods Ltd | Hospitality | 2019 |
| BP3 London Ltd | Wholesale & retail | 2017 |
| BR Barber's Shop Ltd | Wholesale & retail | 2022 |
| Brachetto Ltd | Hospitality | 2023 |
| Bracknell Management Limited | Real estate | 1992 |
| Brada Consulting Ltd | Professional & scientific | 2012 |
| Braderz Limited | Information & communication | 2022 |
| Bradwells Achp Ltd | Energy | 2024 |
| Braintree Electric Forecourt Ltd | Energy | 2016 |
| Bramble Angling Ltd | Agriculture & fishing | 2017 |
| Bramble Digital Ltd | Other services | 2017 |
| Bramble House Day Nursery Limited | Education | 2012 |
| Bramley Technologies Limited | Information & communication | 2015 |
| Branch Joinery and Interiors Ltd | Wholesale & retail | 2016 |
| Brand Commercial South Limited | Professional & scientific | 2024 |
| Brand Hand Ltd | Information & communication | 2016 |
| Brand Monkey Branding Limited | Wholesale & retail | 2022 |
| Brand Monkey Services Ltd | Professional & scientific | 2019 |
| Brand-K Transporting Limited | Wholesale & retail | 2012 |
| Brandy Island Holdings Ltd | Financial services | 2023 |
| Bravapro Ltd | Manufacturing | 2019 |
| Bravedog Ltd | Professional & scientific | 2012 |
| Bravo Cleaning and Home Improvement Services Ltd | Construction | 2021 |
| Bravos Barbershop Limited | Other services | 2025 |
| Bravus Churrascaria Ltd | Hospitality | 2025 |
| Braydon Trailers Ltd | Wholesale & retail | 2023 |
| Brazil COM Farofa Ltd | Hospitality | 2016 |
| Brazil Hair & Beauty Ltd | Other services | 2009 |
| Breakboard Ltd | Information & communication | 2011 |
| Breaking Barriers Reading West LLP | | 2024 |
| Breakspeare Electrical Limited | Construction | 2006 |
| Breasthetics Ltd | Health & social care | 2014 |
| Brebantransport Ltd | Transport & logistics | 2021 |
| Bremels Ltd | Administrative & support | 2024 |
| Brenton Chocolatier Ltd | Manufacturing | 2023 |
| Brenton International Limited | Administrative & support | 2024 |
| Bressan Ltd | Transport & logistics | 2024 |
| Brett Capital Ltd | Financial services | 2025 |
| Brett Property Developments Ltd | Construction | 2011 |
| Brett Property Holdings Ltd | Financial services | 2022 |
| Brett Property Investments Ltd | Real estate | 2015 |
| Brettingham Gate (Broome Manor) Residents Limited | Households | 1981 |
| Brevity IT Solutions Ltd | Information & communication | 2017 |
| Brew Book Ltd | Hospitality | 2024 |
| Brewka Ltd. | Transport & logistics | 2018 |
| Brian Beckett Distribution Limited | | 1970 |
| Brian Bell Holdings Limited | Financial services | 2026 |
| Brian's Hire Limited | Transport & logistics | 2010 |
| Brichaus Ltd | Real estate | 2025 |
| Brick and Build Ltd | Construction | 2020 |
| Bricks Art Construction Limited | Construction | 2020 |
| Bricks by Bruno Ltd | Real estate | 2025 |
| Brickseller Ltd | Construction | 2021 |
| Brickstosell Ltd | Wholesale & retail | 2026 |
| Brickyard Motorcycles Ltd | Wholesale & retail | 2025 |
| Bridge Builders Ministries | Education | 2010 |
| Bridge Court Newbury Limited | Real estate | 2016 |