| Big Grubs Ltd | Hospitality | 2020 |
| Big JAY Vapes Ltd | Transport & logistics | 2026 |
| Big Jazz Ltd | Other services | 2023 |
| Big MAK Publications Ltd | Information & communication | 2018 |
| Big Marketing Limited | Professional & scientific | 2000 |
| Big Mouth Music Limited | Information & communication | 2001 |
| Big Noise Media Ltd | Information & communication | 2021 |
| Big Ocean Therapy Limited | Health & social care | 2026 |
| Big Rock Climbing Limited | Arts & recreation | 2009 |
| Big Rock Limited | Extraterritorial | 2017 |
| Big Shop Friday Ltd | Manufacturing | 2019 |
| Big Voice Ltd | Professional & scientific | 2019 |
| Big Will Elect Ltd | Construction | 2019 |
| Bigbens Landscaping Ltd | Agriculture & fishing | 2026 |
| Bigbens Removals Ltd | Transport & logistics | 2026 |
| Bigcommerce Japan Limited | Information & communication | 2021 |
| Bigdata Academy Ltd | Information & communication | 2017 |
| Bigdog Media Limited | Information & communication | 2023 |
| Bigger Picture Consulting (UK) Ltd | Professional & scientific | 2014 |
| Bigger Trucking Limited | Transport & logistics | 2021 |
| Biggleswade Management Company Limited | Other services | 2019 |
| Biggleswade Sheet Metal Limited | Financial services | 2025 |
| Bigmore Construction Limited | Construction | 2017 |
| Bigoli Ltd | Manufacturing | 2020 |
| Bigrock People Performance Solutions Ltd | Professional & scientific | 2008 |
| Bikass Care Milton Keynes Limited | Health & social care | 2025 |
| Bike Zone Oxford Limited | Wholesale & retail | 2003 |
| Bike-Eye Products Limited | Wholesale & retail | 2010 |
| Bikesafe Ltd | Other services | 2024 |
| Bikestand Solutions Ltd | Other services | 2024 |
| Bila Properties Ltd | Real estate | 2025 |
| Bilateral Trading Ltd | Construction | 2021 |
| Bilc Drive Ltd | Transport & logistics | 2017 |
| Bill & Artisans Ltd | Manufacturing | 2017 |
| Bill's Minibus & Coach Hire Limited | Transport & logistics | 2012 |
| Billing Fish Bar Limited | Hospitality | 2007 |
| Billing Service Station Ltd. | Wholesale & retail | 1992 |
| Billion U.K. Limited | Manufacturing | 1988 |
| Billionaires Milton Keynes Ltd | Wholesale & retail | 2025 |
| Billionett Consulting Ltd | Professional & scientific | 2026 |
| Billy Burns Consultantcy Ltd. | Information & communication | 2018 |
| Billy Schwer Consulting Limited | Professional & scientific | 2019 |
| Biloba Consultancy Services Limited | Professional & scientific | 2018 |
| Bimglobal Limited | Professional & scientific | 2015 |
| Bims Beauty Ltd | Other services | 2022 |
| Bimwise Solutions Ltd | Professional & scientific | 2025 |
| BIN- Noor Ltd | Real estate | 2025 |
| Binary Base Limited | Information & communication | 2024 |
| Binary Spiders Ltd | Information & communication | 2015 |
| Binzy Building Services Ltd | Construction | 2011 |
| BIO Herbs Ltd | Wholesale & retail | 2021 |
| Biocomplete Ltd | Other services | 2023 |
| Bioluminux Ltd | Health & social care | 2021 |
| Biomed Laboratory Limited | Health & social care | 2022 |
| Biomed Medical Devices Limited | Manufacturing | 2023 |
| Biomedica Limited | Professional & scientific | 2019 |
| Biometric Innovations Limited | Information & communication | 2016 |
| Biopharm Compliance Ltd | Real estate | 2019 |
| Biopower Engineering Limited | Manufacturing | 2022 |
| Biopower Technologies Limited | Manufacturing | 2013 |
| Bioquette Ltd | Other services | 2024 |
| Birch (MK) Ltd | Construction | 2013 |
| Birch Landscapes Limited | Administrative & support | 2014 |
| Birchesholdings Ltd | Real estate | 2025 |
| Birchgala Ltd | Wholesale & retail | 2025 |
| Birchgate Contracts & Consulting Limited | Construction | 2017 |
| Birchlandscapes and Sons Ltd | Construction | 2025 |
| Birchover Residences Limited | Real estate | 2014 |
| Birchtree Group Limited | Construction | 2020 |
| Birdie Investment Group Limited | Real estate | 2023 |
| Birsha Limited | Wholesale & retail | 2018 |
| Birt Holdings Ltd | Real estate | 2014 |
| Biryani in a Box Limited | Hospitality | 2018 |
| Biser&Desi Transport Services Ltd | Transport & logistics | 2025 |
| Bisfom Tech Services Limited | Information & communication | 2019 |
| Bishi Medical Services Limited | Health & social care | 2011 |
| Bishop Home Improvements Limited | Construction | 2021 |
| Bismillah MK Limited | Hospitality | 2020 |
| Bison Transport Ltd | Transport & logistics | 2014 |
| Bissell Metal Polishing Limited | Manufacturing | 2011 |
| Bistro in a BUN Ltd | Hospitality | 2025 |
| Bitcoin Advisor Ltd | Information & communication | 2013 |
| Bitdefender IPR Management Limited | Information & communication | 2010 |
| Bite Size Portfolio Limited Partnership | | 2007 |
| Bite the Carrot Ltd | Wholesale & retail | 2025 |
| Bitmix Consulting Limited | Professional & scientific | 2024 |
| Bitzer Compressors UK LP | | 1992 |
| Bitzer UK Limited | Administrative & support | 2010 |
| BIU MK Ltd | Administrative & support | 2015 |
| Biz-Trans Tech Limited | Information & communication | 2022 |
| Bizarre Love Triangle Ltd | Administrative & support | 2024 |
| Bizerba (U.K.) Limited | Manufacturing | 1983 |
| Bizerba Labels U.K. Ltd | Manufacturing | 2021 |
| Bizie Limited | Information & communication | 2015 |
| Bizlynk Limited | Hospitality | 2025 |
| Biztech Technology Forum Limited | Other services | 2009 |
| Biztrack UK Ltd | Information & communication | 2025 |
| Bizz Assistant Ltd | Professional & scientific | 2021 |
| Bizza Commerce Ltd | Wholesale & retail | 2026 |
| Bizznic UK Limited | Hospitality | 2018 |