| BJ Precision Business Solutions Ltd | Information & communication | 2026 |
| BJK 4980 UK Ltd | Hospitality | 2019 |
| BJV Consulting Ltd | Information & communication | 2018 |
| BK Construction Services Ltd | Construction | 2017 |
| BK Pharma Limited | Professional & scientific | 2023 |
| BK Realty Limited | Real estate | 2024 |
| BKM Environmental Consultancy Ltd | Professional & scientific | 2020 |
| Bkrs Consulting Limited | Wholesale & retail | 2018 |
| BKS Property Limited | Real estate | 2021 |
| Blaby Bookkeepers Ltd | Professional & scientific | 2013 |
| Black & Decker | Administrative & support | 1934 |
| Black & Decker Europe | Professional & scientific | 1984 |
| Black and White London Limited | Manufacturing | 2015 |
| Black Ascend Ltd | Administrative & support | 2025 |
| Black by Nattasha Ltd | Arts & recreation | 2026 |
| Black CAB SPV Ltd | Information & communication | 2022 |
| Black Country Engineering Group Limited | Manufacturing | 2020 |
| Black Diamond Entertainment Ltd | Arts & recreation | 2025 |
| Black Duck Bars and Catering Limited | Hospitality | 2020 |
| Black Ducks Events Ltd | Hospitality | 2022 |
| Black FOX Hospitality Ltd | Hospitality | 2026 |
| Black Gold KO Ltd | Administrative & support | 2023 |
| Black PUP Consulting Ltd | Information & communication | 2026 |
| Black PUP Rentals Ltd | Administrative & support | 2023 |
| Black Revolver Films Limited | Information & communication | 2011 |
| Black Revolver Properties Ltd | Real estate | 2018 |
| Black Rifle Limited | Wholesale & retail | 2015 |
| Black Ronin VS Santa Gold Limited | Wholesale & retail | 2008 |
| Black Rose Design Ltd | Wholesale & retail | 2024 |
| Black Sheep Communications Ltd | Professional & scientific | 2019 |
| Black Shell Store Ltd | Wholesale & retail | 2024 |
| Black Snow Media Limited | Administrative & support | 2025 |
| Black Star MD Ltd | Construction | 2022 |
| Black Swan Candles Ltd | Wholesale & retail | 2020 |
| Black Swan Events Ltd | Professional & scientific | 2009 |
| Black Terrier Consulting Limited | Administrative & support | 2000 |
| Black TIE Boxing Ltd | Arts & recreation | 2025 |
| Black&White Roofing Ltd | Construction | 2019 |
| Blackmyth Limited | Wholesale & retail | 2025 |
| Blackshore Limited | Financial services | 2006 |
| Blacksmith Distribution Limited | Real estate | 2023 |
| Blacksmith Store London Ltd | Wholesale & retail | 2018 |
| Blackstar Amplification Ltd | Manufacturing | 2004 |
| Blackstar Asset Management Limited | Financial services | 2025 |
| Blackstar Instrument Group Limited | Professional & scientific | 2017 |
| Blackthorn Gardens Limited | Extraterritorial | 2016 |
| Blackwell Group Limited | Real estate | 2018 |
| Blackwell Property Management Limited | Real estate | 2021 |
| Blackwell Structural Consultants Ltd | Professional & scientific | 2008 |
| Blahblah Catering Limited | Hospitality | 2020 |
| Blair Consultancy Services Limited | Information & communication | 2022 |
| Blair Productions Limited | Arts & recreation | 2005 |
| Blaise Park Resident Management Company Limited | Households | 2018 |
| Blake Project Planning Limited | Professional & scientific | 2025 |
| Blakemore Management Limited | Construction | 2026 |
| Blakemore Renewables Ltd | Construction | 2024 |
| Blakemoreus Ltd | Construction | 2025 |
| Blakewaters Limited | Construction | 2002 |
| Blaklader Workwear Ltd | Wholesale & retail | 2003 |
| Blanc DE Bierges (Europe) Limited | Manufacturing | 2018 |
| Blank Goods Ltd | Manufacturing | 2021 |
| Blason's Sound & Vision Centre Ltd | Wholesale & retail | 2015 |
| Blaze Consulting Limited | Information & communication | 2018 |
| Blaze Fire Technology Limited | Construction | 2011 |
| Blaze Group Holdings Ltd | Public administration | 2026 |
| Blcns Ltd | Transport & logistics | 2018 |
| Bleat PR Limited | Professional & scientific | 2015 |
| Blenheim Court (Leicester) Management Company Limited | Households | 2015 |
| Bless Pixels Limited | Professional & scientific | 2024 |
| Blessarm Ltd | Extraterritorial | 2022 |
| Blessing Fidel Limited | Education | 2025 |
| Blessing Realty Group Ltd | Real estate | 2025 |
| Blessjabz Ltd | Health & social care | 2022 |
| Bletchley View Limited | Construction | 2018 |
| Blets Lets Ltd | Real estate | 2023 |
| Blets Store Ltd | Transport & logistics | 2023 |
| Bletsoe - Brown Limited | Agriculture & fishing | 1969 |
| Bleu Star Land and Development Limited | Construction | 2004 |
| Blickle Castors & Wheels Ltd | Wholesale & retail | 1991 |
| Blidaru Trans Ltd | Transport & logistics | 2016 |
| Blikys Ltd | Wholesale & retail | 2025 |
| Blind Corner Blinds Limited | Wholesale & retail | 2019 |
| Blind Screens Northampton Ltd | Wholesale & retail | 2024 |
| Blinds MK Limited | Real estate | 2015 |
| Blink Commercial Services Limited | Other services | 1997 |
| Bliss Ltd | Other services | 2025 |
| Blissful Nest Limited | Real estate | 2020 |
| Blisworth FC Trading Limited | Arts & recreation | 2021 |
| Blisworth Gifts and Toys Limited | Wholesale & retail | 2019 |
| Blisworth Mill Management Company Limited | Households | 1999 |
| Blisworth Tunnel Narrowboats Limited | Transport & logistics | 2005 |
| Blitz Pest Control & Drain Clearance Services Ltd | Other services | 2024 |
| BLM Trans Limited | Transport & logistics | 2018 |
| Bloch Transport Ltd | Transport & logistics | 2025 |
| Blockwell Paving Ltd | Construction | 2021 |
| Blonde Cat Books Ltd | Information & communication | 2025 |
| Blonde Cat Publications Ltd | Information & communication | 2025 |
| Blonde Dog Designs Ltd | Wholesale & retail | 2020 |
| Blondies Brewery London Ltd | Manufacturing | 2023 |
| Blood LAB Ltd | Health & social care | 2019 |