| Biovolt Ltd | Manufacturing | 2025 |
| Biovoltmedical Ltd | Manufacturing | 2025 |
| Bippity Boppity Bounce Ltd | Administrative & support | 2024 |
| Birchamp Ltd | Professional & scientific | 2023 |
| Birchwood Motor Centre Ltd | Wholesale & retail | 2019 |
| Bishops Electrical & Building Services Limited | Construction | 2013 |
| Bison Shutters Ltd | Construction | 2025 |
| Bitcoin Billionair Club Ltd | Information & communication | 2020 |
| Bitcoin Education Ltd | Education | 2019 |
| Bizroy Investments UK Limited | Wholesale & retail | 2022 |
| BJO Ltd | Health & social care | 2011 |
| BKC Roofing Limited | Construction | 2016 |
| BKM Construction Ltd | Construction | 2013 |
| BKR Group Solutions Ltd | Construction | 2025 |
| BL Educational & Child Psychology Ltd | Health & social care | 2023 |
| BL Plumbing & Heating Ltd | Construction | 2015 |
| BL Sportswear Ltd | Arts & recreation | 2019 |
| Black Cat Sourdough Limited | Manufacturing | 2024 |
| Black in Projects Ltd | Professional & scientific | 2024 |
| Black Loom Ltd | Hospitality | 2024 |
| Black Moth Barbers and Tattoo Ltd | Other services | 2023 |
| Black Moth Barbers Limited | Other services | 2012 |
| Black Moth Woman Ltd | Other services | 2018 |
| Black Panther Consultancy Ltd | Information & communication | 2020 |
| Blackhorse Properties Limited | Construction | 1978 |
| Blackmore Build's Ltd | Construction | 2020 |
| Blackmore Homes Limited | Real estate | 2007 |
| Blackmore Properties Limited | Real estate | 2025 |
| Blackwall Industrial Solutions Ltd | Construction | 2012 |
| Blackwood Hair Studio Ltd | Transport & logistics | 2026 |
| Bladon Dental Limited | Health & social care | 2015 |
| Blak Box Music Group Ltd | Arts & recreation | 2025 |
| Blake Media Ltd | Information & communication | 2020 |
| Blaze Fireworks Ltd | Other services | 2014 |
| BLB Corringham Ltd | Hospitality | 2024 |
| Blessed Jobs Ltd | Health & social care | 2018 |
| Blitzcare Specialist Cleaning Limited | Transport & logistics | 2018 |
| Bloc Contracts Ltd | Construction | 2015 |
| Bloom Accountancy Limited | Professional & scientific | 2019 |
| Bloom Studio Properties Ltd | Real estate | 2025 |
| Blooming Colour Print Limited | Manufacturing | 2019 |
| Blooming Perfect Florist and Wedding Designer Ltd | Wholesale & retail | 2024 |
| Blossom and Heal Nutrition Ltd | Health & social care | 2016 |
| Blossom Bloom Creations Ltd | Hospitality | 2023 |
| Blossom Blooms Creations CIC | Hospitality | 2023 |
| Blossom House Ltd | Health & social care | 2023 |
| Blue Bear Building Ltd | Construction | 2016 |
| Blue Gerbera Horticulture Limited | Administrative & support | 2016 |
| Blue Healthcare Recruitment Limited | Administrative & support | 2020 |
| Blue Ice Enterprises Ltd | Administrative & support | 2018 |
| Blue Peninsula Properties Ltd | Real estate | 2015 |
| Blue Skies & Sunnies Ltd | Administrative & support | 2024 |
| Blue Sky Supermarket Limited | Wholesale & retail | 2005 |
| Bluebell Cleaning Company Limited | Administrative & support | 2008 |
| Bluebelle Skye Productions Limited | Arts & recreation | 2011 |
| Bluebells Enterprise Limited | Real estate | 2023 |
| Bluecrownexa Limited | Wholesale & retail | 2026 |
| Blunden Property Ltd | Real estate | 2024 |
| BM (Barleymont) Catering & Events Limited | Hospitality | 2015 |
| BM Payroll Services Ltd | Professional & scientific | 2025 |
| Bmahen Consultants Ltd | Professional & scientific | 2023 |
| BMB Security Limited | Administrative & support | 2012 |
| BMG GAS Services Limited | Construction | 2020 |
| BMG Management Services Limited | Professional & scientific | 2026 |
| BMO Solutions Limited | Information & communication | 2008 |
| BMR Estate&Investments Ltd. | Real estate | 2017 |
| BMR Investments Limited | Real estate | 2017 |
| Bmrs Property Ltd | Real estate | 2025 |
| BMS Electrical Limited | Construction | 2017 |
| BMS Nails Ltd | Other services | 2023 |
| Bmss Performing Arts Limited | Arts & recreation | 2014 |
| Bmtg Fighter & Events Limited | Arts & recreation | 2023 |
| BNM Investment Limited | Arts & recreation | 2024 |
| Boad Services Limited | Real estate | 2025 |
| Boateng'Slux Limited | Other services | 2025 |
| Bobb & Karm Property Limited | Construction | 2024 |
| BOD Services Ltd | Transport & logistics | 2015 |
| Bodach MOR Limited | Arts & recreation | 2025 |
| Body Balance Limited | Education | 1994 |
| Body Solution LAB Ltd | Other services | 2024 |
| Boffin Finance Limited | Financial services | 2021 |
| Boheme Wear Limited | Wholesale & retail | 2025 |
| Boiler Buddy Ltd | Construction | 2019 |
| Boka by Palms Ltd | Hospitality | 2025 |
| Boleyn Heating Solutions Limited | Other services | 2016 |
| Bolson Properties Ltd | Real estate | 2019 |
| Bolson U.K Limited | Health & social care | 2008 |
| Bonbon Consulting Limited | Other services | 2023 |
| Bonds & Moore Limited | Professional & scientific | 2009 |
| Bonds Leisure Limited | Arts & recreation | 2024 |
| Bonds of Hornchurch Limited | Real estate | 2015 |
| Bonita Aesthetics Ltd | Other services | 2018 |
| Bons Resource Limited | Administrative & support | 2022 |
| Bonum Lucrum Ltd | Transport & logistics | 2021 |
| Booking & Transport Limited | Wholesale & retail | 2024 |
| Bookxpert Ltd | Wholesale & retail | 2023 |
| Boorman & Carter Accountancy Services Limited | Professional & scientific | 2018 |
| Boost Educational Ltd | Education | 2020 |
| Booth Todd Limited | Construction | 2006 |
| Borden Computing Limited | Information & communication | 1992 |