| B & K Heating Limited | Construction | 2011 |
| B & M Courier Services Limited | Transport & logistics | 2024 |
| B & R 2016 Ltd | Hospitality | 2016 |
| B & S Brickwork Limited | Construction | 2013 |
| B & S Hairdressing Trin Gwallt CYF. | Other services | 2017 |
| B & Soll Painting Limited | Construction | 2018 |
| B & W Builders Ltd | Construction | 2014 |
| B & W Electrical (South Wales) Limited | Construction | 2006 |
| B 42 Ltd | Arts & recreation | 2023 |
| B and B Building Ltd | Construction | 2023 |
| B and B Hardware & Plumbing Supplies Ltd | Wholesale & retail | 2016 |
| B and N Cleaning and Maintenance Services Ltd | Construction | 2025 |
| B B B of C | Arts & recreation | 1997 |
| B B George Limited | Financial services | 2022 |
| B B Medicom Limited | Arts & recreation | 1987 |
| B Bond Consultancy Ltd | Professional & scientific | 2021 |
| B Bounce Cardiff Limited | Arts & recreation | 2021 |
| B Browne & Co Ltd | Hospitality | 2014 |
| B Carey Plumbing & Heating Ltd | Construction | 2019 |
| B Coached Ltd | Education | 2025 |
| B Daniels Training Limited | Education | 2025 |
| B Fit Group Limited | Financial services | 2021 |
| B G Engineers Limited | Manufacturing | 2017 |
| B Good Consulting Ltd | Administrative & support | 2017 |
| B H-H Heating and Plumbing Ltd | Construction | 2019 |
| B Healthcare Limited | Health & social care | 2015 |
| B Holland Fabrication Services Limited | Manufacturing | 2013 |
| B Ireland Ltd | Other services | 2019 |
| B J Lalpet Ltd | Transport & logistics | 2019 |
| B K MAX Ltd | Hospitality | 2015 |
| B Milton Electrical (Cardiff) Ltd | Construction | 2024 |
| B Nails Ltd | Other services | 2022 |
| B Promotions Ltd | Administrative & support | 2026 |
| B R Stubbs Limited | Financial services | 2013 |
| B S B Building and Civils Ltd | Construction | 2019 |
| B S Harris Ltd | Real estate | 2025 |
| B Sawz Ltd | Wholesale & retail | 2025 |
| B Scaled Ltd | Information & communication | 2025 |
| B Small Consultancy Limited | Administrative & support | 2017 |
| B Squared Construction Ltd | Administrative & support | 2017 |
| B Sure B Safe Ltd | Professional & scientific | 2002 |
| B Trade Ltd | Wholesale & retail | 2020 |
| B Willis Consulting Limited | Professional & scientific | 2016 |
| B Wilson Services Ltd | Construction | 2014 |
| B&B Audio Concepts Limited | Wholesale & retail | 2003 |
| B&B Billericay Ltd | Hospitality | 2020 |
| B&B Business Centre Limited | Professional & scientific | 2007 |
| B&B Business Limited | Wholesale & retail | 2016 |
| B&B Cardiff Ltd | Hospitality | 2026 |
| B&B Mechanical Ltd | Manufacturing | 2020 |
| B&E Capital Ltd | Financial services | 2025 |
| B&K Holdings 1 Ltd | Real estate | 2023 |
| B&M Fibre Optic Supplies Ltd | Construction | 2026 |
| B&M Rail Company Ltd | Administrative & support | 2016 |
| B&O Sasa Global Limited | Construction | 2020 |
| B&P Catering Ltd | Hospitality | 2018 |
| B&R Holdings Ltd | Financial services | 2021 |
| B&R Scaffolding Limited | Construction | 2017 |
| B&S Design and Build Ltd | Construction | 2019 |
| B&S Exterior and Interior Group Ltd | Construction | 2026 |
| B&T Fish Properties Limited | Real estate | 2026 |
| B'Nourishd Ltd | Wholesale & retail | 2026 |
| B-R Cargo & Removal Services Ltd | Transport & logistics | 2023 |
| B.A. Group International Ltd | Wholesale & retail | 2020 |
| B.A.C Cleaning (Cheshire) Limited | Other services | 2015 |
| B.B Home Delivery Specialist Ltd | Transport & logistics | 2018 |
| B.B. E-Commerce Ltd | Wholesale & retail | 2018 |
| B.B.S Maintenance Services Ltd | Professional & scientific | 2026 |
| B.D.B.C. (UK) Limited | Construction | 1998 |
| B.E.T Social Work Solutions Ltd | Health & social care | 2014 |
| B.G.S. Industrial Limited | Wholesale & retail | 1996 |
| B.I.A International Limited | Professional & scientific | 2025 |
| B.O.T.I. Guard Limited | Administrative & support | 2015 |
| B.R.A.I.N. Biotechnology Research and Information Network UK 2 Limited | Financial services | 2018 |
| B.R.Suman Consultancy Limited | Professional & scientific | 2015 |
| B.S.T.Warehouses Limited | Construction | 1960 |
| B1 Consultancy Ltd | Professional & scientific | 2023 |
| B1 LV Trading Limited | Hospitality | 2023 |
| B11 Ltd | Professional & scientific | 2025 |
| B11 Vans & Cars Limited | Construction | 2019 |
| B1TTERBLUE Limited | Real estate | 2019 |
| B2 Landlord Limited | Households | 2012 |
| B2B Business Developing Ltd | Professional & scientific | 2017 |
| B2B Experts Ltd | Energy | 2019 |
| B2B IT Services Holdings Limited | Financial services | 2021 |
| B2B IT Services Limited | Information & communication | 2004 |
| B2B Jade Ltd | Administrative & support | 2024 |
| B2B Loans & Mortgages Limited | Financial services | 2006 |
| B2CONTROL Ltd | Professional & scientific | 2018 |
| B2I Services Ltd | Wholesale & retail | 2011 |
| B34RBG Limited | Arts & recreation | 2020 |
| B4 Consultants Ltd | Professional & scientific | 2019 |
| B42 Community Amateur Athletics Club Ltd | Arts & recreation | 2026 |
| B42SPIN Ltd | Arts & recreation | 2025 |
| BA Consultancy Group Ltd | Professional & scientific | 2025 |
| BA Partners LLP | | 2024 |
| BA Property Developments (Cardiff) Limited | Real estate | 2018 |
| Baab LDN Ltd | Information & communication | 2019 |
| Baahi Group Ltd | Financial services | 2024 |
| Baahi Services Ltd | Hospitality | 2024 |