| Bebb Kane Aviation Holdings Limited | Transport & logistics | 2023 |
| Beeyond Limited | Education | 2003 |
| Beili Glas CYF | Agriculture & fishing | 2003 |
| BEN Dufty Limited | Agriculture & fishing | 2019 |
| BEN Soal Family Butchers Ltd | Wholesale & retail | 2026 |
| Ben@Floorit! Limited | Extraterritorial | 2022 |
| Bendigo 9-10 Ltd | Real estate | 2007 |
| Benjamin Poole Carpets Ltd | Construction | 2019 |
| Benjamin Soal Property Company Ltd | Real estate | 2026 |
| Bermontgroup Ltd | Wholesale & retail | 2016 |
| Berrell Building Contractors Limited | Construction | 2004 |
| Best Friends K9 Hotel Limited | Other services | 2021 |
| Best Price Stone Ltd | Wholesale & retail | 2013 |
| Bethan Robinson Ltd | Professional & scientific | 2020 |
| Bevan-Jones & Co Limited | Hospitality | 2011 |
| BGS Home Improvements Ltd | Construction | 2022 |
| Bhuiya Properties UK Ltd | Real estate | 2026 |
| Bibado Ltd. | Manufacturing | 2014 |
| Biosample Hub | Professional & scientific | 2020 |
| Biosample Management Limited | Professional & scientific | 2017 |
| Birdshill Biomass Ltd. | Construction | 2015 |
| Birdshill Employee Ownership Trustee Ltd | Professional & scientific | 2023 |
| Bishop & Daughters Limited | Transport & logistics | 2022 |
| Bishops Grove (Lamphey) Management Company Limited | Households | 2013 |
| Bite & Go Ltd | Hospitality | 2022 |
| Bite & Go Pasta.Com Limited | Hospitality | 2026 |
| Bite and Go Deliveries Limited | Hospitality | 2026 |
| Bjc-Uk (Estates) Ltd | Agriculture & fishing | 2011 |
| Black Falcon Ltd | Information & communication | 2005 |
| Black Mountain Business Services Ltd | Administrative & support | 2025 |
| Blackrock Operations Limited | Professional & scientific | 2015 |
| Blacktree Limited | Real estate | 2021 |
| Blaeneifed Farms Limited | Agriculture & fishing | 2003 |
| Blaenwaun Garage Ltd | Wholesale & retail | 2014 |
| Blasus Delicatessen Limited | Wholesale & retail | 2012 |
| Blasus Welshcakes Ltd | Manufacturing | 2023 |
| Blossom ABA Ltd | Education | 2020 |
| BLU Plastering Limited | Construction | 2019 |
| Blue Hawk Services Limited | Professional & scientific | 2021 |
| Blue Mountain Group Ltd | Financial services | 2017 |
| Blue Mountain Security Ltd | Administrative & support | 1999 |
| Blue Mountain Training Ltd | Education | 2017 |
| Blue Sky Engineering UK Ltd | Manufacturing | 2009 |
| Blue Slate Property Ltd | Construction | 2026 |
| Blue Street Property Limited | Real estate | 2024 |
| Blue Vantage Ltd | Information & communication | 2024 |
| BLUE71 Limited | Hospitality | 2018 |
| Blueridge Estates Limited | Real estate | 2000 |
| Bluewave Taxis Limited | Transport & logistics | 2022 |
| Bobby Howells Plant Hire Limited | Construction | 2025 |
| Bodlon@Whitchurch Road Limited | Extraterritorial | 2017 |
| Bodoli Ltd | Manufacturing | 2022 |
| Boobo Tea Carmarthen Limited | Hospitality | 2026 |
| Boundless Inspiration Limited | Professional & scientific | 2017 |
| Boutique Lettings Hereford Limited | Real estate | 2025 |
| Bowen & Weaving Limited | Wholesale & retail | 2002 |
| Box Barn Enterprises Ltd | Hospitality | 2021 |
| Brach Co. Ltd | Real estate | 2017 |
| Bragdy Pererin Co Limited | Wholesale & retail | 2023 |
| Brandie Holdings Ltd | Financial services | 2025 |
| Brandie Trading & Collectibles Ltd | Wholesale & retail | 2026 |
| Brandsforless Limited | Wholesale & retail | 2025 |
| Branford Building Conservation Ltd | Construction | 2018 |
| Branwood Kitchens LLP | | 2025 |
| Brechfa Mountain Bike Club CIC | Arts & recreation | 2022 |
| Brechfau Holdings Limited | Real estate | 2018 |
| BRF Holdings Limited | Professional & scientific | 2020 |
| Brian Rock Limited | Construction | 2019 |
| Brightfix Limited | Construction | 2000 |
| Bro'R Holl Saint Holdings Limited | Households | 2018 |
| Broadharbour Leisure Ltd. | Real estate | 2023 |
| Brocklis Bitumen Ltd | Construction | 2010 |
| Brolec Electrical Services Ltd | Construction | 2013 |
| Brolec Solar Services Ltd | Construction | 2022 |
| Bromfield Services Ltd | Hospitality | 2025 |
| Bromyard Bodyworx Limited | Wholesale & retail | 2019 |
| Bronifach Ltd | Financial services | 2022 |
| Bronte Beach Properties Ltd | Households | 2025 |
| Brook Hill Accountancy Services Limited | Professional & scientific | 2009 |
| Browne & Dixon Ltd | Professional & scientific | 2026 |
| Brownhill Caravan Park Limited | Hospitality | 2019 |
| Bryn Stores Community Shop Limited | Wholesale & retail | 2003 |
| Bryncyrnau Limited | Construction | 2015 |
| Brynderwen Care Home Limited | Real estate | 2002 |
| Bryndir Ltd | Professional & scientific | 2024 |
| Bubbles, Bounce & Sensory Play C.I.C. | Professional & scientific | 2025 |
| Buckskin Holdings Ltd | Real estate | 2023 |
| Buffers Cleaning Management Limited | Administrative & support | 2007 |
| Bull's EYE Lantern Ltd | Information & communication | 2010 |
| Bulldog Tube Straightening Services Limited | Construction | 2020 |
| Bullock Consulting Ltd | Construction | 2005 |
| Bumbledown Limited | Agriculture & fishing | 2021 |
| Bunny and MOO Ltd | Manufacturing | 2020 |
| Burke Contracts Limited | Construction | 1995 |
| Burke Plant Hire Ltd | Administrative & support | 2022 |
| Burlington Asset Management (NO.1) Limited | Hospitality | 2020 |
| Burlington Asset Management Limited | Professional & scientific | 2014 |
| Burlington Legal Management (NO.1) Limited | Professional & scientific | 2016 |
| Bushmill Trade PC | | 2019 |
| BY Nicola Anderson Ltd | Wholesale & retail | 2020 |