| BK ELY Ltd | Hospitality | 2025 |
| BKK (ELY) Ltd | Real estate | 2002 |
| BKR SET and Store Ltd | Transport & logistics | 2023 |
| BL Holdco Limited | Financial services | 2023 |
| Black Monday Ltd | Professional & scientific | 2014 |
| Black Rock Inns Limited | Hospitality | 2012 |
| Blackburn Consulting Group Limited Partnership | | 2023 |
| Blackwell Original Drums Limited | Manufacturing | 2013 |
| Blair R Holdings Limited | Real estate | 2023 |
| Blaise Biogas Limited | Energy | 2018 |
| Blakey Holdings Ltd | Financial services | 2018 |
| Blockmoor Associates Ltd | Professional & scientific | 2013 |
| Blockmoor Ltd | Information & communication | 2023 |
| Bloom Seed Bidco Limited | Financial services | 2024 |
| Blooming Youth Community Interest Company | Health & social care | 2025 |
| Blue Donkey Limited | Administrative & support | 1999 |
| Blue in Art Ltd | Wholesale & retail | 2021 |
| Blue Pebble Technology Ltd | Manufacturing | 2017 |
| Blue Room Consulting Ltd | Information & communication | 2020 |
| Blueboxcreative Limited | Administrative & support | 2015 |
| Bluevane Limited | Administrative & support | 2008 |
| Blush ELY Limited | Wholesale & retail | 2018 |
| BM Aerial & Television Services Limited | Administrative & support | 2010 |
| Bnraji Ltd | Extraterritorial | 2025 |
| Boat Haven Marine Services Ltd | Manufacturing | 2024 |
| Boatserv Ltd | Manufacturing | 2019 |
| BON Creppe & Coffee Ltd | Hospitality | 2026 |
| Boniface Holdings Limited | Financial services | 2023 |
| Bonsai Dynamics Limited | Information & communication | 2025 |
| Boofie Dais Holdings Limited | Financial services | 2018 |
| Boon Event Staffing Ltd | Hospitality | 2023 |
| Boostfocal Limited | Financial services | 2002 |
| Boot & Barrow Ltd | Information & communication | 2026 |
| Border Farm Properties Limited | Financial services | 2016 |
| Border Farm Timber Limited | Wholesale & retail | 2012 |
| Borzellino Property Management (BPM) Ltd | Real estate | 2019 |
| Boss Elite CIC | Education | 2020 |
| Bounce NO.1 Limited | Administrative & support | 2022 |
| Bovingdons Limited | Real estate | 2015 |
| Bradshaw's Engineering Ltd | Wholesale & retail | 2020 |
| Bramley Bale Ltd | Manufacturing | 2024 |
| Brasher & Sons Construction Limited | Construction | 2018 |
| Braybrooke OIL Tanks Limited | Construction | 2024 |
| Breck Gardens Management Limited | Households | 2020 |
| Breeze Technology Limited | Information & communication | 2013 |
| Brick Company Games Limited | Information & communication | 2024 |
| Bridge Boatyard (ELY) Limited | Professional & scientific | 1971 |
| Brigg Lane Biogas Limited | Energy | 2016 |
| Brightpath Cleaning Services Ltd | Administrative & support | 2025 |
| Brington Farm Limited | Agriculture & fishing | 2018 |
| Britanniasitesolutions Limited | Information & communication | 2025 |
| British Society of Plant Breeders Limited(The) | Professional & scientific | 1966 |
| Broad Associates Limited | Professional & scientific | 1994 |
| Broadley Energy Limited | Professional & scientific | 2016 |
| Brodielec Ltd | Construction | 2021 |
| Broker SOT Limited | Wholesale & retail | 1997 |
| Bronco Global Limited | Administrative & support | 2022 |
| Brow LAB by Anna Ltd | Other services | 2021 |
| Brown Bear Books Limited | Information & communication | 2010 |
| Browserealestate Ltd | Construction | 2023 |
| Bruyneel Homes Limited | Construction | 2016 |
| BSC Associates Ltd | Professional & scientific | 2003 |
| Btmm Property Ltd | Real estate | 2018 |
| BTS Core Properties Ltd | Real estate | 2025 |
| Buangoen Limited | Hospitality | 2018 |
| Buckingham & Sparrow Limited | Construction | 1966 |
| Builderly Ltd | Construction | 2020 |
| Buildsure Paving Limited | Other services | 2019 |
| Built Like Butter Ltd | Professional & scientific | 2024 |
| Bumblebee Estates Limited | Real estate | 2024 |
| Bumblebee Fencing Limited | Administrative & support | 2024 |
| Bumps to Babies Limited | Health & social care | 2007 |
| Bunga Truck Ltd | Transport & logistics | 2023 |
| Bunten Pickup Limited | Hospitality | 2006 |
| Burgess Computer Services Limited | Information & communication | 2009 |
| Burj Enterprise Ltd | Information & communication | 2024 |
| Burling Associates Limited | Professional & scientific | 2019 |
| Burner and Combustion Ltd | Manufacturing | 2010 |
| Burton and Co.Services Limited | Professional & scientific | 2025 |
| Burwell Cleaning Ltd | Administrative & support | 2023 |
| Business Bees Ltd | Extraterritorial | 2025 |
| Businessclean (Cambridge) Limited | Administrative & support | 2002 |
| Busitech Limited | Information & communication | 2011 |
| Bustimi Ltd | Wholesale & retail | 2020 |
| Busy BEE Recruitment Limited | Administrative & support | 2017 |
| Buttington Property Limited | Real estate | 2020 |
| Buzz Mortgages Limited | Financial services | 2024 |
| BVB Food Ltd | Hospitality | 2025 |
| BVT Project Management Services Ltd | Construction | 2024 |
| BY Dottie Limited | Information & communication | 2015 |
| Bycamo Ltd | Wholesale & retail | 2023 |
| Byford Consulting Ltd | Professional & scientific | 2026 |
| C & G Franks Limited | Transport & logistics | 1990 |
| C D Clowe Electrical Services Ltd | Construction | 2017 |
| C H Huntingdon Management Company Limited | Real estate | 2012 |
| C J Overy Transport and Crane Hire Limited | Transport & logistics | 2009 |
| C K Electrical Testing Limited | Construction | 2010 |
| C S Transporter Ltd | Transport & logistics | 2024 |
| C&G Bricklaying Contractors Ltd | Extraterritorial | 2024 |
| C&G Construction Contractors Ltd | Construction | 2021 |