| Benjamin Priest Limited | Manufacturing | 1950 |
| Bennie Equipment Limited | Administrative & support | 1967 |
| Bennie Haulage Limited | Transport & logistics | 1974 |
| Bennie Holdings Limited | Professional & scientific | 2008 |
| Bennie Plant Limited | Administrative & support | 1993 |
| Bentley Commercial Consultants Limited | Professional & scientific | 2018 |
| Bergiel Ltd | Wholesale & retail | 2024 |
| Berry & Cross Ltd | Wholesale & retail | 2026 |
| Besecure Computer Systems Limited | Information & communication | 2009 |
| Besleaga Limited | Wholesale & retail | 2016 |
| Bespoke Bridal Bliss Ltd | Wholesale & retail | 2024 |
| Bespoke Health and Safety Ltd | Professional & scientific | 2015 |
| Bespoke Luxe Wigs & Hair Ltd. | Other services | 2020 |
| Bespoke Paint Finishes Limited | Administrative & support | 2015 |
| Best 4 U Mortgages Ltd | Financial services | 1999 |
| Best 4U Estate Planning Ltd | Other services | 2022 |
| Best Asset Investments Limited | Real estate | 2018 |
| Best Asset Limited | Construction | 2015 |
| Best C&M Services Ltd | Manufacturing | 2025 |
| Best Choice Transport Ltd | Transport & logistics | 2015 |
| Best Desborough Pizza Ltd | Hospitality | 2024 |
| Best in Class Software Systems Ltd | Information & communication | 2025 |
| Best Logistics 247 Ltd | Transport & logistics | 2025 |
| Bestfood (Kettering) Ltd | Hospitality | 2025 |
| Bestforyou Accounting Ltd | Professional & scientific | 2024 |
| Beta Byte Limited | Wholesale & retail | 2022 |
| Beth Chloe Tattoos Ltd | Other services | 2023 |
| Better Lives (Northants) Limited | Education | 2008 |
| Better Lives Group Ltd | Financial services | 2024 |
| Better Sourced Deals Ltd | Real estate | 2020 |
| Better Tasting Drinks Co. Limited | Wholesale & retail | 2015 |
| Beulah Afro Hair Salon Ltd | Professional & scientific | 2015 |
| Bevin Properties Limited | Real estate | 2026 |
| Bevom Limited | Professional & scientific | 2019 |
| Bewers Turner & Co LLP | | 2019 |
| Bewlay Consulting Limited | Information & communication | 2007 |
| Beyond Curious Limited | Professional & scientific | 2016 |
| Beyond Speech Speech and Language Therapy Ltd | Health & social care | 2025 |
| Beyond Steel Ltd | Professional & scientific | 2019 |
| Beyond Therapy Limited | Professional & scientific | 2024 |
| BFJ Properties Limited | Real estate | 2024 |
| Bgbet Limited | Arts & recreation | 1996 |
| BGK Property Ltd | Real estate | 2023 |
| Bgnaps Limited | Professional & scientific | 2006 |
| BGO Multi Trade Ltd | Administrative & support | 2021 |
| BH Tools and Equipment Ltd | Wholesale & retail | 2020 |
| BH12345 Ltd | Real estate | 2024 |
| Bhangoo Developments Limited | Other services | 2010 |
| Bhva Axis Hub CIC | Education | 2021 |
| Big Aumais TCG Ltd | Wholesale & retail | 2024 |
| Big Bopper Entertainment Limited | Other services | 2011 |
| Big Grilla BBQ Ltd | Hospitality | 2025 |
| Big-C Creative AI Ltd | Information & communication | 2024 |
| Bigself Ltd | Professional & scientific | 2020 |
| Bigstream Limited | Professional & scientific | 1987 |
| Billing Property Investments Ltd | Real estate | 2025 |
| Billson Steel Ltd | Manufacturing | 2019 |
| Billsons Holdings Limited | Extraterritorial | 2015 |
| Binary Web Solutions Ltd | Professional & scientific | 2016 |
| Bingol Kettering Ltd | Hospitality | 2023 |
| BIO Support Services Limited | Manufacturing | 2002 |
| BIOME9 Limited | Professional & scientific | 2023 |
| Biosolve UK Limited | Professional & scientific | 2025 |
| Birch Systems Ltd. | Construction | 2025 |
| Birchfield Springs Limited | Agriculture & fishing | 2010 |
| Birchwood Utilities Limited | Construction | 2016 |
| Birley Estates Limited | Construction | 1984 |
| Bishop Stopford School | Education | 2011 |
| Bistro Domowe Ltd | Hospitality | 2020 |
| Bistro Vino E Pasta Ltd | Hospitality | 2025 |
| Bizology Ltd | Administrative & support | 2019 |
| BJD Plumbing & Heating Ltd | Construction | 2025 |
| BKL Driving Services Limited | Administrative & support | 2023 |
| BL 2008 Ltd | Administrative & support | 2008 |
| BL One Trading Ltd | Wholesale & retail | 2025 |
| Black INK Accounting Ltd | Professional & scientific | 2026 |
| Black Resin Cosmetics Ltd | Financial services | 2026 |
| Black Titan Solutions Ltd | Wholesale & retail | 2025 |
| Black-Lyon Trading Limited | Financial services | 2024 |
| Blackbox Investments and Property Ltd | Financial services | 2019 |
| Blackbox Pentesters Ltd | Professional & scientific | 2025 |
| Blackbridge Construction Consultancy Ltd | Professional & scientific | 2025 |
| Blackbridge Group Holdings Limited | Financial services | 2022 |
| Blackbridge Plant Limited | Construction | 2014 |
| Blackcat Management Limited | Professional & scientific | 2021 |
| Blackdown Horticultural Consultants Limited | Agriculture & fishing | 1999 |
| Blackhaven Enterprises Limited | Other services | 2017 |
| Blackhorse Developments 2019 Ltd | Construction | 2019 |
| Blackthorn Marina Limited | Arts & recreation | 2011 |
| Blackwell's of Kettering Ltd | Administrative & support | 2020 |
| Blake Henderson Ltd | Real estate | 2015 |
| Blandford Bespoke Ltd | Construction | 2022 |
| Blandford GAS Services Limited | Manufacturing | 2002 |
| Blandford Management Services Limited | Professional & scientific | 2012 |
| Blandfords LLP | | 2005 |
| BLD Software Limited | Information & communication | 2023 |
| Blecer Limited | Wholesale & retail | 2018 |
| Blivr Ltd | Information & communication | 2024 |
| BLK Limited | Extraterritorial | 1946 |
| BLL Limited | Extraterritorial | 1966 |