| Bespoke Cricket Ltd | Manufacturing | 2021 |
| Beta Graphic Limited | Professional & scientific | 2003 |
| Bettison Clark Ltd | Wholesale & retail | 2025 |
| Beyond Fibre Ltd | Information & communication | 2024 |
| BFG Services Ltd | Manufacturing | 2004 |
| BFP Group Ltd | Wholesale & retail | 2022 |
| Biddles Scrap Metal Ltd | Water & waste | 2007 |
| Big Mango Properties Limited | Real estate | 2024 |
| BIKES2GO Limited | Manufacturing | 2017 |
| Binley Group Ltd | Construction | 2023 |
| Birch Sports Surfaces Limited | Administrative & support | 2006 |
| Biscuit Consultancy Ltd | Professional & scientific | 2023 |
| Bishops Tachbrook Ltd | Transport & logistics | 2021 |
| Blackbrown International Ltd | Professional & scientific | 2012 |
| Blackfriars (Market Harborough) Management Company Limited | Households | 2006 |
| Blackwell's Grazing Company Limited | Real estate | 2020 |
| Blaise Industries Ltd | Professional & scientific | 2017 |
| Bldtst Ltd | Wholesale & retail | 2025 |
| Blinds & Curtains Megastore Ltd | Wholesale & retail | 2016 |
| Bliss Belle Limited | Wholesale & retail | 2026 |
| Bliss Belle Nails Limited | Wholesale & retail | 2026 |
| BLJ Group Holdings Ltd | Professional & scientific | 2025 |
| BLR Investments Ltd | Construction | 2026 |
| BLU Connection Ltd | Wholesale & retail | 2011 |
| Blue Drift Ltd | Professional & scientific | 2025 |
| Blue Noble LLP | | 2017 |
| Blue Ocean HCW Ltd | Other services | 2018 |
| Blue Touch Limited | Professional & scientific | 2007 |
| Blue Windmill Childcare Limited | Other services | 2001 |
| Blueberry Holdco Limited | Wholesale & retail | 2008 |
| Bluefrog Design Limited | Manufacturing | 2003 |
| Blzee Pubs Limited | Hospitality | 2016 |
| BMR UK Properties Limited | Real estate | 2020 |
| Boardwalk Mentoring Limited | Professional & scientific | 2025 |
| BOB Millington Limited | Wholesale & retail | 1996 |
| Bobuild Projects Ltd | Construction | 2020 |
| Boden Bakes Ltd | Manufacturing | 2019 |
| Bohannon International Ltd | Professional & scientific | 2022 |
| Border Merchant Systems Limited | Information & communication | 1990 |
| Borrum Renewables Ltd | Professional & scientific | 2013 |
| Borthwick Investments Ltd | Real estate | 2022 |
| Boston Sidings Limited | Households | 2019 |
| Bosworth Enterprises Limited | Professional & scientific | 2018 |
| Bosworth Leasing Limited | Financial services | 1999 |
| Bowden Consulting Engineers Ltd | Construction | 2012 |
| Bowden Real Estate Limited | Real estate | 2022 |
| Bowden Stores Ltd | Wholesale & retail | 2016 |
| Bowden Studio Ltd | Information & communication | 2026 |
| Box Actuarial Limited | Financial services | 2017 |
| Box Design Limited | Professional & scientific | 1987 |
| Boxed Packaging Ltd | Administrative & support | 2017 |
| Boxitt Ltd | Manufacturing | 2023 |
| Boxx Group Ltd | Real estate | 2020 |
| Brabbsgate Management Company Limited | Households | 2011 |
| Brain Digit Ltd | Information & communication | 2024 |
| Brambillow Accounting Ltd | Professional & scientific | 2020 |
| Bramble Foods Group Holdco Limited | Financial services | 2020 |
| Bramble Foods Limited | Manufacturing | 2007 |
| Bramfield Education Ltd. | Education | 2017 |
| Brammond & Co. Limited | Construction | 1984 |
| Brampton ASH Hotel Investments Limited | Real estate | 2017 |
| Brampton Land and Property Limited | Real estate | 2024 |
| Brandon Purton Limited | Wholesale & retail | 2023 |
| Braybrooke Investments Limited | Real estate | 2011 |
| Braystone Developments Ltd | Construction | 2025 |
| Breathe Digital Solutions Limited | Professional & scientific | 2013 |
| Bredbury Dental Centre Ltd | Health & social care | 2007 |
| Brenstech Limited | Hospitality | 2018 |
| Brett Burrows Limited | Financial services | 2024 |
| Brevitt - Rieker Limited | Wholesale & retail | 1989 |
| Brew Resourceful Ltd | Professional & scientific | 2023 |
| Brewing Trade Ltd | Wholesale & retail | 2023 |
| Brian Holyfield Limited | Households | 1963 |
| Bridgedale Homes Limited | Real estate | 2022 |
| Bright Star (Northampton) Ltd | Hospitality | 2019 |
| Brint Associates Limited | Real estate | 2022 |
| British Damage Management Association | Other services | 1999 |
| Broadcoat Ltd | Real estate | 2018 |
| Broadgate Solutions Limited | Information & communication | 2019 |
| Broadley Properties Limited | Financial services | 2002 |
| Broadpeak Consultants Limited | Professional & scientific | 2011 |
| Broadviews Consulting Ltd | Agriculture & fishing | 2020 |
| Broadway Drives & Patios Ltd | Administrative & support | 2025 |
| Broch Corporate Services LLP | | 2004 |
| Brodrick and Company Limited | Education | 2016 |
| Bromfields Farms Limited | Agriculture & fishing | 1999 |
| Brooke House College Limited | Education | 2019 |
| Brookes & Spencer Learning Technologies Ltd | Education | 2025 |
| Brooklyn Management Services Limited | Professional & scientific | 1986 |
| Brookshaw Holdings Limited | Real estate | 2021 |
| Brookside Carpets and Curtains Limited | Wholesale & retail | 1989 |
| Brothers Executive Search Ltd | Administrative & support | 2023 |
| Brown Sauce Development Limited | Construction | 2019 |
| Brownies Estate Holdings Limited | Real estate | 2017 |
| BRP Architects Limited | Professional & scientific | 2010 |
| Bruce Green Limited | Professional & scientific | 2003 |
| Bryan Investment Group Ltd | Real estate | 2023 |
| Bryan Software Limited | Information & communication | 2022 |
| Buckby Spice Limited | Hospitality | 2025 |
| BUD & Bean Preloved Children’S Sales Ltd | Wholesale & retail | 2024 |