| Bletchley Social Club Limited | Hospitality | 2025 |
| Bletchley Supermarket Limited | Wholesale & retail | 2026 |
| Bletchley Wood Works Ltd | Construction | 2025 |
| Bletchley's Car Clinic Limited | Other services | 2007 |
| Blewett Ltd | Manufacturing | 2026 |
| Bliiss Ltd | Manufacturing | 2018 |
| Blind and Film Company Limited | Construction | 2006 |
| Blind Tiger Cocktails and Events Limited | Hospitality | 2022 |
| Blindmatrix Limited | Information & communication | 2010 |
| Blink Invest Ltd | Real estate | 2020 |
| Blink IT Limited | Information & communication | 2024 |
| Blip VFX Productions Limited | Information & communication | 2010 |
| Blipcraft Studios Limited | Information & communication | 2026 |
| Bliss Ventures LLP | | 2025 |
| Bliss Woof Limited | Professional & scientific | 2013 |
| Blissful Properties Limited | Real estate | 2023 |
| Blistex Limited | Manufacturing | 1963 |
| Blitz Mechanical Services Ltd | Other services | 2014 |
| Block 524 ROW 6 Limited | Professional & scientific | 2017 |
| Block C 9 the Upper Drive Limited | Households | 2023 |
| Block One Design & Engineering Ltd | Manufacturing | 2023 |
| Block Two Technology Ltd | Manufacturing | 2018 |
| Blockworks Group Ltd | Hospitality | 2013 |
| Blockyard Limited | Construction | 2016 |
| Blog Heads Ltd | Professional & scientific | 2025 |
| Blokproperty Ltd | Real estate | 2022 |
| Bloom Branch Limited | Real estate | 2015 |
| Bloom Finance Ltd | Information & communication | 2020 |
| Bloom Island Ltd | Wholesale & retail | 2025 |
| Bloom Project Consulting Ltd | Professional & scientific | 2024 |
| Bloom Virtual Limited | Professional & scientific | 2025 |
| Bloom Womens Health LLP | | 2025 |
| Bloombridge Recruitment Limited | Administrative & support | 2011 |
| Bloomer Homes Ltd | Real estate | 2018 |
| Bloomer Homes Midlands Ltd | Real estate | 2018 |
| Bloomline Distribution Limited | Wholesale & retail | 2025 |
| Bloomsbury Stud Limited | Agriculture & fishing | 1966 |
| Blossom ARK Ltd | Information & communication | 2023 |
| Blossom Carers Ltd | Administrative & support | 2017 |
| Blossom Education Consultancy Ltd | Education | 2019 |
| Blossom Global Solutions Ltd | Health & social care | 2023 |
| Blossom Tree Day Nursery Limited | Education | 2015 |
| Blossoms Solutions Ltd | Health & social care | 2026 |
| Bloxham Consultancy UK Ltd | Professional & scientific | 2025 |
| BLP Chemists Limited | Wholesale & retail | 2006 |
| BLS Sportswear & PPE Equipment Limited | Manufacturing | 2021 |
| Blsr Property Limited | Real estate | 2019 |
| BLT Stokesay Limited | Real estate | 2022 |
| BLU Betty UK Limited | Wholesale & retail | 2023 |
| BLU Contractor Limited | Construction | 2011 |
| BLU Digital Group Limited | Information & communication | 2012 |
| BLU Petal Home Care Ltd | Public administration | 2023 |
| BLU Star Limited | Administrative & support | 2012 |
| Blue Alligator Company Limited | Information & communication | 1983 |
| Blue Alligator Holdings Limited | Information & communication | 2022 |
| Blue and Gray Limited | Administrative & support | 2024 |
| Blue Aspen Technologies UK Limited | Information & communication | 2015 |
| Blue Badge Limited | Professional & scientific | 2001 |
| Blue Bear Property Limited | Real estate | 2016 |
| Blue Bell Holdings Limited | Financial services | 2018 |
| Blue Box Financials Ltd | Professional & scientific | 2024 |
| Blue Chilli Group Ltd | Administrative & support | 2025 |
| Blue Chimp IT Limited | Information & communication | 2016 |
| Blue COW Tractors Limited | Administrative & support | 2016 |
| Blue DOC Limited | Health & social care | 2016 |
| Blue DOT Thinking Limited | Information & communication | 2016 |
| Blue Flame (MK) Limited | Construction | 2010 |
| Blue Frog Properties Ltd | Real estate | 2016 |
| Blue Gemstone Limited | Information & communication | 2017 |
| Blue Glass Ventures Ltd | Administrative & support | 2021 |
| Blue Griffin Ltd | Professional & scientific | 2017 |
| Blue Group Food Services Limited | Hospitality | 2024 |
| Blue Hawk Accountants Ltd | Professional & scientific | 2024 |
| Blue Heaven Real Estate Ltd | Real estate | 2025 |
| Blue Hectare Associates Limited | Professional & scientific | 2020 |
| Blue Jellybean Ltd | Information & communication | 2020 |
| Blue Krait Security Limited | Administrative & support | 2019 |
| Blue Leaf Properties Limited | Transport & logistics | 2019 |
| Blue Leopard Property Limited | Real estate | 2022 |
| Blue Lion Property Limited | Real estate | 2021 |
| Blue Lotus 360 Ltd | Information & communication | 2021 |
| Blue Lotus Healthcare Ltd | Health & social care | 2020 |
| Blue Mist Limited | Real estate | 2012 |
| Blue Moon Vintners Limited | Hospitality | 2007 |
| Blue Nature Limited | Real estate | 2020 |
| Blue North Sustainability Ltd | Professional & scientific | 2018 |
| Blue Oak Manufacturing Limited | Manufacturing | 2013 |
| Blue Oak Property Ltd | Real estate | 2025 |
| Blue Payroll & Recruitment Services Ltd | Administrative & support | 2022 |
| Blue Peak Builders Limited | Construction | 2025 |
| Blue Pelican Holdings | Financial services | 2023 |
| Blue Pigeon Exim UK Ltd | Wholesale & retail | 2017 |
| Blue Rock CAP A4 Limited | Other services | 2025 |
| Blue Rock Homes Ltd | Construction | 2025 |
| Blue Rose Logistics Limited | Professional & scientific | 2025 |
| Blue Services Limited | Other services | 2023 |
| Blue Sky Advisory Services Limited | Professional & scientific | 2025 |
| Blue Sky Aviation Catering Ltd | Hospitality | 2019 |
| Blue Sky Estates Limited | Real estate | 2011 |
| Blue Sky Fine Foods Ltd | Hospitality | 2020 |