| Buildings 3A, 3B & 4 Harbourside Management Company Limited | Households | 2007 |
| Builta Ltd | Construction | 2018 |
| Buku Solutions Limited | Construction | 2023 |
| Bulaila Limited | Wholesale & retail | 2025 |
| Bulgarian School DR Petar Beron Reading Ltd | Education | 2017 |
| Bulk UP Ltd | Wholesale & retail | 2025 |
| Bull's Shed Limited | Hospitality | 2026 |
| Bullcourt Flat Management Company Limited | Households | 1980 |
| Bullers Arms Ltd | Hospitality | 2017 |
| Bullet 13 Limited | Transport & logistics | 2024 |
| Bulletpoint Copy Limited | Professional & scientific | 2016 |
| Bulloak Ltd | Manufacturing | 2021 |
| Bullyache Ltd | Arts & recreation | 2022 |
| Bulmershe Gymnastics Club | Arts & recreation | 1996 |
| Bulmershe Properties Limited | Real estate | 2025 |
| Bulstrode Farm (Holdings) Limited | Agriculture & fishing | 1967 |
| Bumble B Property Agents Limited | Real estate | 2022 |
| Bumbles and BOO Ltd | Wholesale & retail | 2018 |
| Bumpers Solar Limited | Energy | 2015 |
| Bunga Consulting Ltd | Information & communication | 2026 |
| Bunker Harris Limited | Wholesale & retail | 2010 |
| Bunnyaf Ltd | Wholesale & retail | 2025 |
| Buoyancy Health Strategy Ltd | Professional & scientific | 2025 |
| Buraq Technology Ltd | Information & communication | 2026 |
| Buratta`S Limited | Hospitality | 2003 |
| Burgau Apartment LLP | | 2017 |
| Burgeon Investments UK Ltd | Real estate | 2015 |
| Burger DEN Reading Limited | Hospitality | 2024 |
| Burgess Jewellery Ltd | Wholesale & retail | 2025 |
| Burghfield Bridge Tyres Ltd | Wholesale & retail | 2007 |
| Burghfield Community Sports Association | Arts & recreation | 2009 |
| Burghfield Estates Limited | Real estate | 2008 |
| Burghfield Mill Limited | Households | 2000 |
| Burghfield Recording Studio Ltd | Information & communication | 2019 |
| Burghfield Residents CIC | Arts & recreation | 2024 |
| Burghfield RS Ltd | Other services | 2023 |
| Burghfield Sailing Company Limited | Arts & recreation | 1987 |
| Burghley Investments Limited | Real estate | 2019 |
| Burgschneider Ltd | Wholesale & retail | 2024 |
| Burguesa Limited | Professional & scientific | 2023 |
| Burley Consulting (Europe) Ltd | Professional & scientific | 2018 |
| Burlington Legal Management Limited | Professional & scientific | 2015 |
| Burnden Square Limited | Professional & scientific | 2021 |
| Burnham Steam & Historic Machinery Club Ltd | Other services | 2015 |
| Burrell Digital Ltd | Information & communication | 2016 |
| Burrows Management Limited | Households | 2001 |
| Burst Gang Ltd | Wholesale & retail | 2023 |
| Burstchase Limited | Real estate | 1986 |
| Burstx Limited | Transport & logistics | 2025 |
| Burtonwood Heritage | Arts & recreation | 2000 |
| Buscalibre UK Ltd | Wholesale & retail | 2023 |
| Bushman AV Limited | Construction | 2025 |
| Business Cloud Solutions Ltd | Information & communication | 2015 |
| Business Driven Solutions Limited | Information & communication | 2002 |
| Business Enhancers Limited | Professional & scientific | 2012 |
| Business Insight and Accounting Solutions Ltd | Professional & scientific | 2023 |
| Business Mentoring Limited | Administrative & support | 2017 |
| Business Momentum Ltd | Professional & scientific | 2001 |
| Business Moves Group Limited | Professional & scientific | 2003 |
| Business Scaler Ltd | Information & communication | 2024 |
| Business Solutions PVT Limited | Professional & scientific | 2018 |
| Business Systems Group (UK) Limited | Information & communication | 2007 |
| Business Technology Enablement Ltd | Information & communication | 2025 |
| Business Tycoon Ltd | Real estate | 2020 |
| Business Worldwide Limited | Other services | 2011 |
| Busy BEE Construction Limited | Construction | 2024 |
| Busy BEE Wholesale Limited | Wholesale & retail | 2024 |
| Busy Kangaroos Ltd | Construction | 2017 |
| Busybuyer Ltd | Real estate | 2020 |
| Butcher Joe's Ltd | Wholesale & retail | 2024 |
| Butler and Butler Ltd | Hospitality | 2025 |
| Butler Electrical Services Ltd | Construction | 2025 |
| Butlers Services Agri Limited | Agriculture & fishing | 2013 |
| Butlers Services Lettings Ltd | Real estate | 2018 |
| Butlers Services Ltd | Water & waste | 2016 |
| Butt Property Limited | Real estate | 2023 |
| Butt Zain Limited | Wholesale & retail | 2021 |
| Buttar Transport Limited | Transport & logistics | 2025 |
| Butterbur & Sage International Public Limited Company | Extraterritorial | 1995 |
| Butterbur and Sage Limited | Manufacturing | 1983 |
| Butterfly Building Services Limited | Construction | 2025 |
| Butterfly Itsm Limited | Information & communication | 2017 |
| Butterscotch Design Ltd | Professional & scientific | 2010 |
| Butts International Limited | Administrative & support | 1980 |
| Butts Investments Ltd | Real estate | 2025 |
| Butts Kiosk Ltd | Wholesale & retail | 2026 |
| Butts Properties 2 Ltd | Real estate | 2025 |
| Butts Properties Limited | Real estate | 2022 |
| Buxshalls Estate Management Company Limited | Households | 2022 |
| Buyspree Limited | Wholesale & retail | 2022 |
| Buzatu Trans Limited | Wholesale & retail | 2020 |
| Buzley Hall Consultants Ltd | Information & communication | 2020 |
| Buzz GRC Consulting Limited | Other services | 2018 |
| Buzz Gym Limited | Arts & recreation | 2013 |
| Buzz Gym Swindon Ltd | Arts & recreation | 2015 |
| Buzz Gym UK Limited | Arts & recreation | 2005 |
| Buzzbloom Limited | Wholesale & retail | 2026 |
| Buzzify Ltd | Wholesale & retail | 2025 |
| Buzzing Bees Childcare Solution Limited | Health & social care | 2025 |
| BV Pharma Ltd | Health & social care | 2015 |