| Borthwicks PHS Ltd | Construction | 2017 |
| BOS Accounting Ltd | Professional & scientific | 2025 |
| Boss Contract Solutions Ltd | Construction | 2015 |
| Boss Fitness Limited | Arts & recreation | 2018 |
| Boston & Boston Ltd | Professional & scientific | 2012 |
| Bounder & CAD Limited | Information & communication | 2014 |
| Bourne & Co Estates Ltd | Real estate | 2024 |
| Bourne and Co Technologies Ltd | Information & communication | 2026 |
| BOW Trust (Durham) Limited(The) | Arts & recreation | 1983 |
| Bowburn Indian Ltd | Hospitality | 2024 |
| Bowburn Music & Performing Arts C.I.C. | Arts & recreation | 2020 |
| Bowburn North Ltd | Real estate | 2015 |
| Bowcock Security Services / ILM Associates Ltd | Administrative & support | 2011 |
| Bowesfield Management Company Limited | Real estate | 2004 |
| Box 37 Ltd | Wholesale & retail | 2025 |
| Boyd Consulting Limited | Professional & scientific | 2012 |
| Boyle Homes Ltd | Real estate | 2026 |
| BPD Holdings Ltd | Financial services | 2024 |
| Brad Burton Limited | Professional & scientific | 2009 |
| Bradleyden Ltd | Real estate | 2025 |
| Brambledown Contracts Group Limited | Wholesale & retail | 2011 |
| Brambledown Landscape Services Limited | Construction | 1972 |
| Bramhall Hospitality Limited | Hospitality | 2016 |
| Bramwells Elvet Limited | Wholesale & retail | 2014 |
| Branchford Group Ltd | Professional & scientific | 2024 |
| Branchwalkers NE Landscapes Limited | Administrative & support | 2024 |
| Branden Property Limited | Real estate | 2006 |
| Brandon Happytimes Daycare Limited | Education | 2005 |
| Brandon Village Nursery Limited | Professional & scientific | 2011 |
| Branksome Booze & Convenience Limited | Wholesale & retail | 2017 |
| Brass Tacks Consulting Limited | Professional & scientific | 2012 |
| BRC Textile Ltd | Wholesale & retail | 2025 |
| Breakfast Tea Ltd | Hospitality | 2025 |
| Brechin Turner Limited | Health & social care | 2003 |
| Bregazzi and Starr Construction Limited | Water & waste | 2016 |
| Bremner Property Holdings Ltd | Real estate | 2024 |
| Brenton Commercial Ltd | Construction | 2024 |
| Brett Bros. Developments Limited | Construction | 1986 |
| Brewery Shaft (Nmcs) Ltd | Extraterritorial | 2016 |
| Briar PMC Limited | Professional & scientific | 2016 |
| Brickie Bro’S Ltd | Construction | 2025 |
| Brickstone Group Ltd | Construction | 2022 |
| Bridge Studio Art CIC | Education | 2024 |
| Bridgedales Nutrition Limited | Wholesale & retail | 2005 |
| Bridgez Ltd | Information & communication | 2024 |
| Bright Cosy Homes Limited | Real estate | 2024 |
| Brighter Futures Children's Services Ltd | Health & social care | 2026 |
| Brightstar Venture Group Ltd | Financial services | 2025 |
| Brisda Properties Ltd | Real estate | 2019 |
| Brit Cars (International) Limited | Wholesale & retail | 2012 |
| Britedgetrading Ltd | Wholesale & retail | 2024 |
| Britons Anglia Limited | Real estate | 2019 |
| Britshop LLC Limited | Wholesale & retail | 2025 |
| BRK Global Ltd | Wholesale & retail | 2025 |
| Broken Cross Energy SPV Limited | Real estate | 2023 |
| Broken Cross Windfarm SPV Limited | Real estate | 2023 |
| Brooke Anderson Consulting Engineers Limited | Professional & scientific | 2008 |
| Brookes Outfitters & Tailors Limited | Wholesale & retail | 2004 |
| Brooks Construction NE Limited | Construction | 2025 |
| Brookson (5144K) Limited | Administrative & support | 2007 |
| Brookwood Outdoors Education CIC | Education | 2017 |
| Broom House Durham Limited | Agriculture & fishing | 2019 |
| Broomhouse Care Limited | Administrative & support | 2009 |
| Brown SAW Limited | Manufacturing | 2025 |
| Brown's Boathouse Limited | Manufacturing | 1976 |
| Browns Auto Services Limited | Wholesale & retail | 2005 |
| Browns Coalyard Limited | Real estate | 2018 |
| Browns Enterprises Ltd | Real estate | 2021 |
| Browns Hairdressing Limited | Other services | 2007 |
| Brows and Blush Limited | Other services | 2021 |
| BRQ Recovery Ltd | Transport & logistics | 2024 |
| Brsl Limited | Professional & scientific | 2016 |
| Bruder Property Limited | Real estate | 2007 |
| Bryden Polymer Trading Ltd | Professional & scientific | 2026 |
| BS Heating Solutions (NE) Limited | Construction | 2021 |
| Bs@Bs Limited | Hospitality | 2018 |
| BT Joinery Ltd | Construction | 2017 |
| Bubblecat Ltd | Education | 2010 |
| Buckley Medical Limited | Health & social care | 2022 |
| Buford Court Management Limited | Extraterritorial | 2001 |
| Build Secure INS Ltd | Financial services | 2021 |
| Build Secure Ltd | Financial services | 2021 |
| Buildbright Contractors Ltd | Construction | 2025 |
| Building Blocks of Communication Ltd | Education | 2025 |
| Building Culture CIC | Arts & recreation | 2016 |
| Building Wiring Solutions Limited | Construction | 2011 |
| Bullivant Agricultural Limited | Manufacturing | 2021 |
| Bulman Property Limited | Administrative & support | 1969 |
| Bulmer Construction Ltd | Construction | 2017 |
| Bunker Pumps UK Ltd | Wholesale & retail | 2024 |
| Burghley Partners Ltd | Administrative & support | 2021 |
| Burn Hall Estates Management Limited | Households | 1997 |
| Burns & Sons Limited | Construction | 2025 |
| Burns Petcare Ltd | Other services | 2020 |
| Burnside Joinery Limited | Construction | 2015 |
| Burntclay Civils Ltd | Construction | 2020 |
| Burntclay Civils NE Ltd | Construction | 2026 |
| Burntclay Construction Limited | Construction | 2017 |
| Burton Design's Ltd | Manufacturing | 2025 |
| BUS Monkeys Ltd | Wholesale & retail | 2016 |