| Biznav Kent Limited | Professional & scientific | 2023 |
| Biznav Limited | Professional & scientific | 2012 |
| Biznav Orpington Limited | Real estate | 2016 |
| Bizness Buddies Ltd | Information & communication | 2009 |
| Bizzell Property Co. Limited(The) | Construction | 1978 |
| Bj's Bouncy Castles Limited | Arts & recreation | 2009 |
| BJK 68 Ltd | Hospitality | 2024 |
| BKP Property Ltd | Households | 2020 |
| Bl-Wright Ltd | Other services | 2021 |
| Black Arrow Holding Limited | Real estate | 2024 |
| Black Harbour Management Limited | Professional & scientific | 2025 |
| Black Haus Interiors Limited | Professional & scientific | 2021 |
| Black Hawkstone Ltd | Construction | 2024 |
| Black in the Ballroom CIC | Education | 2023 |
| Black Professional Services Collective C.I.C. | Information & communication | 2021 |
| Black Sea Tiles Limited | Wholesale & retail | 1996 |
| Blackator Productions Limited | Professional & scientific | 2008 |
| Blackbrook Mews Management Company Limited | Households | 2013 |
| Blackhaus Consultants Limited | Professional & scientific | 2020 |
| Blackhaus Developments Limited | Professional & scientific | 2012 |
| Blackhaus Properties Limited | Professional & scientific | 2021 |
| Blackheath & Bromley Harriers AC. | Arts & recreation | 1926 |
| Blackline Cladding Ltd | Wholesale & retail | 2026 |
| Blackline Projects Limited | Construction | 2026 |
| Blackman Painters Ltd | Construction | 2025 |
| Blackridge Roofing Ltd | Construction | 2026 |
| Blacksmith Court Development Limited | Administrative & support | 2022 |
| Blackthorn House (Romford) RTM Company Limited | Real estate | 2016 |
| Blanford House Residents Limited | Households | 1988 |
| Blaze Fire Protection Paint Systems Ltd. | Construction | 2007 |
| BLC Buildings Ltd | Construction | 2021 |
| Blenbrom Property Company Limited | Real estate | 2026 |
| Blessly Limited | Wholesale & retail | 2024 |
| Blinc & Corporation Ltd | Administrative & support | 2025 |
| Bliss Relocation Limited | Hospitality | 2024 |
| Blmc Building Services Ltd | Construction | 2026 |
| Block & Press Ltd | Wholesale & retail | 2021 |
| Blocksafe Facility Services Limited | Construction | 2025 |
| Blooms in Hayes Limited | Wholesale & retail | 2025 |
| Blooms London Ltd | Wholesale & retail | 2022 |
| Bloomsbury Management (1982) Leytonstone Limited | Households | 1982 |
| Bloomsbury Mansions RTM Company Limited | Households | 2021 |
| Blossom and Ruby Services Ltd | Health & social care | 2015 |
| Blossom Consultancy Limited | Hospitality | 2010 |
| Blossom Housing and Support Ltd | Administrative & support | 2022 |
| Blossom Springs Limited | Real estate | 2021 |
| Blossom Technology Solutions Limited | Information & communication | 2015 |
| Blower and Wingfield Properties Limited | Real estate | 2025 |
| Blue Apple Accountants Ltd | Professional & scientific | 2015 |
| Blue Building (London) RTM Company Limited | Real estate | 2025 |
| Blue Crayon Limited | Professional & scientific | 2017 |
| Blue Dolphin Consultants Limited | Administrative & support | 2015 |
| Blue GEM International Ltd | Wholesale & retail | 2025 |
| Blue Gradient Ltd | Professional & scientific | 2025 |
| Blue Indigo Limited | Other services | 2005 |
| Blue London Limited | Professional & scientific | 2020 |
| Blue Lozenge Limited | Professional & scientific | 2021 |
| Blue Marlin Ltd | Real estate | 2011 |
| Blue Pearl DRY Cleaners Limited | Other services | 2017 |
| Blueapple Services Limited | Professional & scientific | 2007 |
| Bluebell Farm (Kent) Limited | Agriculture & fishing | 2018 |
| Blueberry Property Management and Lettings Limited | Real estate | 2021 |
| Bluefish Bar Limited | Hospitality | 2024 |
| Bluegrass Restaurants Ltd | Hospitality | 2013 |
| Bluemint Co Technologies Limited | Information & communication | 2025 |
| BLUEMOON1 Limited | Extraterritorial | 2023 |
| Bluepond Properties Limited | Households | 1998 |
| Blueport Research Limited | Wholesale & retail | 2025 |
| Blueprinted Visions Limited | Manufacturing | 2025 |
| Bluesky Digital Consult Limited | Information & communication | 2021 |
| Bluestone Electrical Services Ltd | Construction | 2007 |
| Bluetrip Motor Limited | Extraterritorial | 2025 |
| Bluewake Ltd | Extraterritorial | 2026 |
| Bluezone for Life Limited | Information & communication | 2026 |
| Blush & Ivory Limited | Wholesale & retail | 2015 |
| BM Partners VCC Ltd | Administrative & support | 2012 |
| Bmaria Electronics Limited | Wholesale & retail | 2023 |
| BMB Mortgages Ltd | Professional & scientific | 2013 |
| BMC Homes Limited | Construction | 2011 |
| Bmdecs Painting Contractors Ltd | Construction | 2024 |
| BMK & Co UK Ltd | Real estate | 2019 |
| Boardtransit Couriers Ltd | Transport & logistics | 2026 |
| Bodi & Co UK Ltd | Health & social care | 2018 |
| Bodies by Design Ltd | Health & social care | 2015 |
| Bognor Property Limited | Real estate | 2025 |
| Boiler Repair Ltd | Construction | 2015 |
| Bold Build Ltd | Construction | 2020 |
| Bollano Plumbers Limited | Construction | 2014 |
| Bolst Ltd | Information & communication | 2024 |
| Bolt Golf Limited | Arts & recreation | 2025 |
| Bolt Leisure Limited | Hospitality | 2025 |
| Bolt Padel Limited | Arts & recreation | 2025 |
| Bolt Production and Post Limited | Information & communication | 2019 |
| Bolti FW UK Holding LLP | | 2024 |
| Bomartech Ltd | Other services | 2023 |
| Bon-Bleu Limited | Wholesale & retail | 2025 |
| Bond 50 Ukeig | | 2009 |
| Bonding School Nurseries Limited | Education | 2023 |
| Boodas Business Services Limited | Health & social care | 2013 |
| Bookedops Ltd | Information & communication | 2025 |