| Big Business Intelligence Limited | Information & communication | 2015 |
| Big Chef Catering Ltd | Hospitality | 2019 |
| Big China Cardiff Ltd | Hospitality | 2024 |
| Big City International Ltd | Real estate | 2019 |
| Big Daddy Rubbish Clearance Ltd | Water & waste | 2026 |
| Big Deez Ltd | Manufacturing | 2017 |
| Big Dreamer Productions Ltd | Arts & recreation | 2017 |
| Big EYE Deers Limited | Information & communication | 2007 |
| Big FAN Trading Co., Ltd | Wholesale & retail | 2021 |
| Big Fish Building Consultancy Limited | Professional & scientific | 2020 |
| Big Fish Chippy Limited | Hospitality | 2025 |
| Big Fish Consulting Limited | Manufacturing | 2014 |
| Big Fish Records Ltd | Arts & recreation | 2023 |
| Big Galaxy Ltd | Wholesale & retail | 2019 |
| Big HIT Hub Ltd | Wholesale & retail | 2025 |
| Big Jacks Peri Peri Ltd | Hospitality | 2020 |
| Big K'S Kitchen Ltd | Hospitality | 2023 |
| Big Little Films Ltd | Information & communication | 2018 |
| Big Malky Ltd | Administrative & support | 2013 |
| Big Mama Store Limited | Wholesale & retail | 2020 |
| Big Mamma's Sandwich Club Ltd | Hospitality | 2024 |
| Big News Trading Ltd | Wholesale & retail | 2015 |
| Big Plast Ltd | Construction | 2014 |
| Big Tick Limited | Administrative & support | 2007 |
| Big Wooden Horse (UK) Ltd | Arts & recreation | 2010 |
| Big Works Ltd | Manufacturing | 2019 |
| Big YAK Media Limited | Professional & scientific | 2025 |
| Bigaloo Ltd | Financial services | 2004 |
| Bigbang Print Limited | Wholesale & retail | 2020 |
| Bigben Movers Limited | Transport & logistics | 2025 |
| Bigcrad Limited | Mining & quarrying | 2026 |
| Bigdealshops Ltd | Wholesale & retail | 2025 |
| Bigfoot Services Ltd | Extraterritorial | 2003 |
| BIGMUNCHSPOLTT@53 Ltd | Hospitality | 2025 |
| Bigness Group Limited | Construction | 2017 |
| Bigpicturex Ltd | Administrative & support | 2021 |
| Bihlas Services Ltd | Wholesale & retail | 2021 |
| Biire Casasign Ltd | Wholesale & retail | 2022 |
| Biizz 365 Ltd | Wholesale & retail | 2023 |
| Biju Thomas Limited | Professional & scientific | 2007 |
| BIL Investments Ltd | Real estate | 2016 |
| Bilad AL Shaam | Health & social care | 2013 |
| Bilal Moukhlis Ltd | Wholesale & retail | 2025 |
| Bilal Shahid Ltd | Wholesale & retail | 2025 |
| Bilbiz Global PLC | Professional & scientific | 2012 |
| Bilbo LLP | | 2011 |
| Bild MCA (UK) Limited | Construction | 2020 |
| Bildbase Ltd | Information & communication | 2026 |
| Bilgeson Limited | Real estate | 2020 |
| Bill Way & Co.Limited | Wholesale & retail | 1953 |
| Billar Ocasion Ltd | Wholesale & retail | 2025 |
| Billesley Convenience Store Limited | Wholesale & retail | 2016 |
| Billflow Management Services Limited | Information & communication | 2025 |
| Billionaire Business Ltd | Other services | 2025 |
| Billione Rikko Ltd | Administrative & support | 2013 |
| Billstock Limited | Wholesale & retail | 2021 |
| Billy Goat Grips Ltd | Information & communication | 2014 |
| Billyioon Limited | Wholesale & retail | 2019 |
| Bilmate Information Communication Technologies Ltd | Information & communication | 2025 |
| Bilow Capital Ltd | Financial services | 2022 |
| Bima Care Ltd | Health & social care | 2024 |
| Bimage Ltd | Professional & scientific | 2017 |
| Bimappolis Limited | Hospitality | 2017 |
| Bimmarc Limited | Wholesale & retail | 2023 |
| Bimmer Elite Limited | Wholesale & retail | 2018 |
| Bimz Global Ltd | Professional & scientific | 2026 |
| Binarshad Ltd | Wholesale & retail | 2025 |
| Binary Communications Ltd | Information & communication | 2018 |
| Binary Mediacom Inc. Limited | Professional & scientific | 2025 |
| Binbevel Limited | Households | 1981 |
| Bineezy Business Ltd | Transport & logistics | 2023 |
| Bing Digital Ltd | Information & communication | 2023 |
| Bingati Retail Limited | Wholesale & retail | 2026 |
| Bingham Hall Partnership Limited | Construction | 2005 |
| Bingo Group Ltd | Water & waste | 2011 |
| Bingo Industries Ltd | Water & waste | 2006 |
| Bingo Nederland Ltd | Arts & recreation | 2025 |
| Bingo Recycling Ltd | Water & waste | 2006 |
| Bingo Resources Ltd | Water & waste | 2011 |
| Bingo Waste Ltd | Water & waste | 2006 |
| Bingothon C.I.C. | Arts & recreation | 2021 |
| Bink Outdoor Limited | Manufacturing | 2018 |
| Binky Events Limited | Other services | 2017 |
| Binmac Limited | Wholesale & retail | 2023 |
| Binnan Developments Ltd | Wholesale & retail | 2026 |
| Bintraders Limited | Wholesale & retail | 2023 |
| BIO Alliance PC | | 2017 |
| BIO Marketing Limited | Professional & scientific | 2024 |
| Biocatalysts Limited | Manufacturing | 1990 |
| Biocertica Ltd | Professional & scientific | 2022 |
| Biocide Consult Limited | Professional & scientific | 2015 |
| Biodexa Ltd | Professional & scientific | 2000 |
| Biodexa Pharmaceuticals (Wales) Limited | Professional & scientific | 2003 |
| Biodexa Pharmaceuticals PLC | Professional & scientific | 2014 |
| Biofiora BIO Technology Ltd | Professional & scientific | 2025 |
| Biohacking Nutrition Ltd | Wholesale & retail | 2020 |
| Biohermes Diagnostics Limited | Extraterritorial | 2019 |
| Biointeligent Ltd | Health & social care | 2025 |
| Biologic AI Ltd | Information & communication | 2025 |
| Bioman Services Limited | Manufacturing | 2012 |