| Bizzwax Investment Limited | Information & communication | 2020 |
| BJ Neat & Nurture Ltd | Administrative & support | 2025 |
| BJ Yuan Ltd. | Wholesale & retail | 2025 |
| BJE Properties Ltd | Real estate | 2017 |
| BJM Housing Limited | Real estate | 2019 |
| BK Electrical (MK) Ltd | Construction | 2026 |
| BK Finance Global Ltd | Professional & scientific | 2026 |
| BK Hunter Ltd | Manufacturing | 2018 |
| BK Renovations Limited | Professional & scientific | 2006 |
| BK Training & Consulting Limited | Professional & scientific | 2019 |
| BKA Estates Limited | Real estate | 2026 |
| BKS Electrical Services Ltd | Construction | 2025 |
| BKSZ1 Ltd | Wholesale & retail | 2023 |
| BL Design & Construction Consultancy Limited | Professional & scientific | 2017 |
| Bl-Av Limited | Construction | 2023 |
| Black & White Training Limited | Professional & scientific | 2018 |
| Black and Old Gold Solutions Limited | Information & communication | 2017 |
| Black Belt Ventures Ltd | Wholesale & retail | 2024 |
| Black Box Echo Ltd. | Arts & recreation | 2014 |
| Black Capital Partners Ltd | Real estate | 2019 |
| Black Cat Accounts Ltd | Professional & scientific | 2012 |
| Black Commercial Limited | Real estate | 2012 |
| Black Crow Training Ltd | Arts & recreation | 2025 |
| Black Diamond Advisory UK Ltd | Information & communication | 2021 |
| Black ELK Heating Limited | Professional & scientific | 2023 |
| Black ELK Home Surveys Limited | Other services | 2009 |
| Black HAT Services Limited | Administrative & support | 2020 |
| Black HAT Trading Ltd | Wholesale & retail | 2020 |
| Black Knight Retail Systems LLP | | 2013 |
| Black Label Security Ltd | Administrative & support | 2026 |
| Black Lion Security Ltd | Administrative & support | 2025 |
| Black Salt Limited | Information & communication | 2001 |
| Black Wolf Media Limited | Professional & scientific | 2017 |
| Blackbeard Group Limited | Real estate | 2021 |
| Blackbeard Technologies Ltd | Professional & scientific | 2025 |
| Blackberry Way Management (NO.2) Limited | Households | 1990 |
| Blackbird Audio Limited | Information & communication | 2018 |
| Blackbird Capital Partners Limited | Professional & scientific | 2016 |
| Blackbird Innovations Ltd | Information & communication | 2024 |
| Blackbird Solicitors Limited | Professional & scientific | 2017 |
| Blackcollectives Limited | Wholesale & retail | 2020 |
| Blackened Sun Brewing Company Limited | Manufacturing | 2017 |
| Blackfish Brands Ltd | Manufacturing | 2021 |
| Blackfriars Tax Solutions LLP | | 2010 |
| Blackhawk Group Ltd | Information & communication | 2015 |
| Blackline Conversions Limited | Manufacturing | 2026 |
| Blackmore Signalling Solutions (BSS) Limited | Professional & scientific | 2023 |
| Blackout Entertainment Ltd | Arts & recreation | 2017 |
| Blackridge Build Ltd | Construction | 2026 |
| Blackseed Education Ltd | Information & communication | 2013 |
| Blackshire Limited | Information & communication | 2019 |
| Blackthorn Property Investment Company Limited | Real estate | 2022 |
| Blackthorn Research Services Limited | Information & communication | 2025 |
| Blacktop Auto Group Limited | Wholesale & retail | 2026 |
| Blackwell Legal Ltd | Professional & scientific | 2025 |
| Blackwood Chase Consultants Limited | Professional & scientific | 2019 |
| Blackwood Chase Ltd | Professional & scientific | 2007 |
| Blackwood Composites Ltd | Manufacturing | 2014 |
| Blaco Property Ltd | Real estate | 2020 |
| Blad International Limited | Health & social care | 2015 |
| Blades Dolls Ltd | Other services | 2026 |
| Blae Media Ltd | Professional & scientific | 2020 |
| Blajin Construction Limited | Construction | 2025 |
| Blake Shipping Ltd | Transport & logistics | 2026 |
| Blakeburn Brothers Ltd | Professional & scientific | 2020 |
| Blakeney Estates Limited | Construction | 2000 |
| Blakeney Homes (Breachwood Green) Limited | Construction | 2024 |
| Blakeney Homes (Developments) Limited | Construction | 2022 |
| Blakeney Homes (Ickleford) Limited | Construction | 2025 |
| Blakeney Homes Holdings Limited | Financial services | 2023 |
| Blakeney Homes Limited | Construction | 2012 |
| Blakeney Strategic Land Limited | Real estate | 2025 |
| Blakes Painting & Decorating Limited | Construction | 2017 |
| Blanes MGT Limited | Administrative & support | 2016 |
| Blank Canvas Group Limited | Other services | 2023 |
| Blash Consult Ltd | Other services | 2016 |
| Blaze Sprinkler Protection Ltd | Construction | 2025 |
| Blazetech Systems Ltd | Manufacturing | 2025 |
| BLE Toois Ltd | Wholesale & retail | 2025 |
| Bleeks Signature Ltd | Wholesale & retail | 2017 |
| Blend Milkshakes Ltd | Other services | 2019 |
| Blenheim Executive Limited | Transport & logistics | 2021 |
| Blenheim Property Services Group Ltd | Real estate | 2020 |
| Blerrie Lekker Ltd | Wholesale & retail | 2015 |
| Blessed Elegance by Ella Ltd | Other services | 2024 |
| Blessed PAM Childcare Limited | Education | 2025 |
| Blessing's Care Ltd | Health & social care | 2013 |
| Blessings Care Group Ltd | Real estate | 2020 |
| Blessings Gallery Limited | Professional & scientific | 2018 |
| Bletchley Construction Ltd | Professional & scientific | 2014 |
| Bletchley Masonic Events Ltd | Hospitality | 2023 |
| Bletchley Masonic Hall Limited | Real estate | 1971 |
| Bletchley Park Capital Partners Limited | Real estate | 2004 |
| Bletchley Park Company Limited | Administrative & support | 1992 |
| Bletchley Park Property Developments Limited | Construction | 2012 |
| Bletchley Park Trust Limited | Arts & recreation | 1992 |
| Bletchley PJ Pizza Limited | Hospitality | 2019 |
| Bletchley Printing Shop Limited | Manufacturing | 2024 |
| Bletchley Rugby Club Limited | Arts & recreation | 2009 |
| Bletchley Scaffolding Ltd | Construction | 2020 |