| Avitus International Limited | Financial services | 2019 |
| AVM Construction and Engineering Ltd | Construction | 2025 |
| Awakened Gatherings Ltd | Hospitality | 2023 |
| Awards Admin Ltd | Administrative & support | 2017 |
| Awasix Holdings Ltd | Wholesale & retail | 2019 |
| Aylin Kebab Ltd | Hospitality | 2023 |
| B & a Cranes Limited | Other services | 1995 |
| B Maddocks Rugby Ltd | Professional & scientific | 2024 |
| B N Griffiths Limited | Information & communication | 2007 |
| B&O Photography Service Ltd | Wholesale & retail | 2020 |
| B.D. Williams & Sons (Butchers) Limited | Wholesale & retail | 1998 |
| B.T.S. Haulage Limited | Transport & logistics | 1985 |
| Baby Swimming Carmarthenshire LLP | | 2017 |
| Back to Basics Care & Training Limited | Health & social care | 2013 |
| Bar Luna Limited | Hospitality | 2020 |
| Bark & Bound Limited | Other services | 2021 |
| Bark Wales Limited | Professional & scientific | 2003 |
| Barleybind 2 Health Care Limited | Real estate | 2013 |
| Barleybind Properties Ltd | Real estate | 2022 |
| Barnett & Jones Plastering Ltd | Construction | 2014 |
| Barraclough Carey Productions Limited | Information & communication | 1985 |
| Barratt Associates Ltd | Professional & scientific | 2019 |
| Basmati Cross Hands Ltd | Hospitality | 2022 |
| Bassline IT Limited | Information & communication | 2024 |
| Baton Twirling Association Cymru | Other services | 2020 |
| Bawar's Barber Ltd | Other services | 2025 |
| Baysoft Software Solutions Ltd | Information & communication | 2013 |
| Baytree Property Rentals Ltd | Real estate | 2016 |
| BE Insured Ltd | Administrative & support | 2019 |
| BE Seen Content Limited | Information & communication | 2023 |
| Bear & Claude Limited | Manufacturing | 2015 |
| Bear Human Resources Limited | Administrative & support | 2019 |
| Bear Property Solutions Ltd | Real estate | 2022 |
| Beaufort Medical Imaging Limited | Health & social care | 2015 |
| Beaute Boutique Limited | Professional & scientific | 2015 |
| Beautifully Made Limited | Manufacturing | 2017 |
| Becker (Sliding Partitions) Limited | Construction | 1986 |
| BEE Different Ltd | Wholesale & retail | 2013 |
| BEE Trendy Ltd | Wholesale & retail | 2025 |
| Beefy’S Vehicle Transport and Recovery Limited | Transport & logistics | 2026 |
| Beerpark Ltd | Wholesale & retail | 2020 |
| Bellator Properties Ltd | Real estate | 2023 |
| Bemedsafe Limited | Health & social care | 2018 |
| BEN O'Connor Electrical Services Limited | Construction | 2019 |
| Ben's Barber Shop Ltd | Other services | 2024 |
| Berwick Boarding Kennels Ltd | Administrative & support | 2018 |
| Bespoke Electrical Home Services Limited | Construction | 2020 |
| Bespoke Home WDC Limited | Construction | 2026 |
| Bessent and Bessent Limited | Construction | 2015 |
| Best Choice Plumbing Limited | Construction | 2025 |
| Better Days Restoration Limited | Manufacturing | 2019 |
| Bevans Developments Ltd | Real estate | 2025 |
| Biddulph Arms Ltd | Hospitality | 2022 |
| Big Farma Limited | Professional & scientific | 2021 |
| Biker at Heart Ltd | Extraterritorial | 2021 |
| Bink Broadband Ltd | Information & communication | 2005 |
| Bink Group Ltd | Information & communication | 2005 |
| Bisbo Property Limited | Construction | 2017 |
| Bitfields Limited | Information & communication | 2017 |
| Black Door Property Group Ltd | Real estate | 2023 |
| Black Horse Marketing Limited | Professional & scientific | 2007 |
| Black Mountain Asset Solutions Ltd | Real estate | 2023 |
| Black Spring Investments Limited | Financial services | 2025 |
| Bladescope Access Ltd | Construction | 2025 |
| Blaen Treweryll CYF | Households | 2024 |
| Blaenhiraeth Farming Limited | Agriculture & fishing | 2013 |
| Blaidd CYF | Information & communication | 2023 |
| Blaine Transport Ltd | Transport & logistics | 2022 |
| Blinds of Elegance Limited | Manufacturing | 1984 |
| Blossomy Ltd | Real estate | 2024 |
| Blue Planet Schools Ltd | Education | 2022 |
| Blue Whale Gifts Limited | Wholesale & retail | 2014 |
| Bondale Limited | Administrative & support | 2009 |
| Bookaspark Ltd | Other services | 2024 |
| Boss Construction & Developments Ltd | Construction | 2024 |
| Boughan Panteg Stores Limited | Wholesale & retail | 2020 |
| Bowcon Ltd | Real estate | 2024 |
| Boxform Limited | Construction | 2025 |
| Boyar Armoury Ltd | Wholesale & retail | 2022 |
| Brew Coffee Club Ltd | Wholesale & retail | 2025 |
| Bridlewise Ltd | Information & communication | 2014 |
| Brightley Ltd | Professional & scientific | 2011 |
| Brilliant Mortgages Limited | Financial services | 2007 |
| Brit Educational Ltd | Education | 2022 |
| Brockington Bellows Limited | Extraterritorial | 2003 |
| Brockington Group International Limited | Extraterritorial | 2003 |
| Brodyr Properties Limited | Real estate | 2023 |
| Brown Maze Group Limited | Administrative & support | 2017 |
| Browns Recycling Group Limited | Water & waste | 2014 |
| Browns Waste Management and Recycling Limited | Water & waste | 2003 |
| BRT Doorway Diggers Ltd | Construction | 2026 |
| Bruce Charles Commercials Ltd | Wholesale & retail | 2020 |
| BRV CYF | Professional & scientific | 2021 |
| Brynamman Self Storage Limited | Administrative & support | 2022 |
| Bryncelyn Enterprises Limited | Professional & scientific | 2003 |
| Brynfuwch CYF | Financial services | 1979 |
| Brynteg Farm and Wellbeing Sanctuary Ltd | Education | 2021 |
| Brynteg Services Ltd | Other services | 2025 |
| Bryntirion Apartments 1-6 RTM Company Limited | Households | 2010 |
| Bszi Limited | Financial services | 2019 |