| Best Grocery Retail Swansea Ltd | Wholesale & retail | 2026 |
| Bestco Surfacing Limited | Construction | 1987 |
| Beste Ltd | Wholesale & retail | 2018 |
| Beta Lett Ltd | Real estate | 2024 |
| Better Care London Limited | Health & social care | 2019 |
| Betterbreaks Ltd | Information & communication | 2025 |
| Betterconnected Limited | Professional & scientific | 2016 |
| Betty Recruitment Limited | Administrative & support | 2009 |
| Beyond Care Limited | Health & social care | 2019 |
| Beyond Visual Appeal Ltd | Wholesale & retail | 2024 |
| Bezired Ltd | Real estate | 2018 |
| BFC Accountants Ltd | Professional & scientific | 2026 |
| BFT Properties Limited | Real estate | 2017 |
| BG Vita Import Export Ltd | Wholesale & retail | 2022 |
| Bgfiresolution Ltd | Construction | 2025 |
| BH Managing Limited | Construction | 2019 |
| Big Bite (London) Limited | Hospitality | 2005 |
| Big Ximes Limited | Arts & recreation | 2019 |
| Bilimway Training and Consultancy Ltd | Other services | 2016 |
| Billy's Autocare Ltd | Administrative & support | 2024 |
| Billys Childcare Services Ltd | Health & social care | 2022 |
| Biloosh UK Limited | Wholesale & retail | 2023 |
| Biosafe Ltd | Professional & scientific | 2019 |
| Birchtree Limited | Professional & scientific | 2024 |
| Birdie Spirits Limited | Wholesale & retail | 2024 |
| Biri Services Ltd | Construction | 2020 |
| Bishop's Stortford Residential Management Company Limited | Households | 1999 |
| Bishopsgate Apartments LLP | | 2006 |
| Bishopsgate Apartments NO 2 LLP | | 2010 |
| Bitis Brands Limited | Wholesale & retail | 2023 |
| BJW Electrical Limited | Construction | 2018 |
| BK Properties & Construction Ltd | Real estate | 2023 |
| BKG Estates Ltd | Real estate | 2025 |
| BKH Consulting Ltd | Administrative & support | 2018 |
| Black Dog Group Limited | Construction | 2015 |
| Black GAS Plumbing and Heating Ltd | Construction | 2025 |
| Black Oak Property Group Ltd | Real estate | 2020 |
| Black Olives Event Catering Ltd | Extraterritorial | 2021 |
| Black Rabbit Cars Limited | Transport & logistics | 2025 |
| Black Women in Scripted (Bwis) Ltd | Information & communication | 2024 |
| Blackbird Marketing Group Ltd | Information & communication | 2023 |
| Blackdale Holdings Limited | Financial services | 2023 |
| Blackdale Properties Limited | Real estate | 2023 |
| Blake & AJB Resources Limited | Real estate | 2024 |
| Blake Knight Ltd | Professional & scientific | 2016 |
| Blanco Toro Limited | Construction | 2024 |
| Blend Pilates Ltd | Arts & recreation | 2025 |
| Blind Scouse Limited | Real estate | 2022 |
| Blobbies Ltd | Wholesale & retail | 2020 |
| Block a Phase 4 Colindale Management Limited | Households | 2015 |
| Bloom Building Services Ltd | Professional & scientific | 2023 |
| Bloom Cafe Limited | Hospitality | 2010 |
| Blossom Bites Cafe and Tea Rooms Ltd | Hospitality | 2023 |
| Blossom Haus Ltd | Wholesale & retail | 2026 |
| BLU Vision Consulting Ltd | Professional & scientific | 2021 |
| Blue Horizon Logistics Ltd | Transport & logistics | 2025 |
| Blue River Home Care Ltd | Health & social care | 2017 |
| Blue SAW Limited | Real estate | 2016 |
| Bluebrick Property Development Ltd | Construction | 2025 |
| Bluebug Holdings Limited | Financial services | 2023 |
| Bluebyu London Limited | Wholesale & retail | 2025 |
| Blueprint for Health Ltd | Wholesale & retail | 2015 |
| Bluesmart Ltd | Hospitality | 2012 |
| Bluetops Limited | Information & communication | 2014 |
| BM Entertainment Ltd | Information & communication | 2020 |
| BMI Electrical Solutions Ltd | Construction | 2018 |
| BNG Units Limited | Professional & scientific | 2024 |
| BNV Electricals Ltd | Construction | 2024 |
| Bobtail Fruit Limited | Wholesale & retail | 2009 |
| Bogdan Catering Ltd | Manufacturing | 2020 |
| Boiken’S Builds Ltd | Construction | 2026 |
| Boiler Install Ltd | Construction | 2023 |
| Bold Blueprints Construction Ltd | Construction | 2023 |
| Bold Realty Ltd | Real estate | 2023 |
| Bolo Investment Strategies Ltd | Wholesale & retail | 2026 |
| Bons Property Services Ltd | Real estate | 2024 |
| Bonsori Limited | Information & communication | 2026 |
| Bop-Me Ltd | Health & social care | 2012 |
| Borekchi Ltd | Hospitality | 2020 |
| Boss Tyres Ltd | Wholesale & retail | 2023 |
| Botanic Cafe Limited | Hospitality | 2026 |
| Bouncing Bees Ltd | Education | 2012 |
| Bounty Properties Limited | Real estate | 2023 |
| Bourne Close Flats (Ware) Management Company Limited | Households | 1977 |
| Boxing Clever Anger Management Therapy Limited | Education | 2023 |
| Boxx Pizza Limited | Hospitality | 2026 |
| BOZ Kent Limited | Real estate | 2023 |
| Bozkina Properties Ltd | Real estate | 2022 |
| Bpch Land Limited | Financial services | 2022 |
| BPG IS Love Ltd | Other services | 2025 |
| Brackenhurst Vale Ventures Ltd | Wholesale & retail | 2026 |
| Bramble Hill Lodge Limited | Real estate | 2021 |
| Brasil Auto Repairs Limited | Wholesale & retail | 2025 |
| Braveson Holding Ltd | Financial services | 2022 |
| Brazilian Property Investments Limited | Other services | 2007 |
| Breeze TR Ltd | Transport & logistics | 2022 |
| Bregu International Consulting Ltd | Professional & scientific | 2025 |
| Brentwood Centre Management Company Limited | Real estate | 2021 |
| Brentwood Tile Boutique Ltd | Other services | 2015 |
| Brentwood Vehicle Sales Limited | Wholesale & retail | 2017 |