| John Seldon Limited | Transport & logistics | 2014 |
| Joio CBD CYF. | Wholesale & retail | 2020 |
| Jojo's & A'S Beauty Within Training Academy Ltd | Other services | 2023 |
| Jojo's Beauty Within Ltd | Hospitality | 2021 |
| Jones & Lloyd Roofing Supplies Ltd | Wholesale & retail | 2026 |
| Jones & Purslow Limited | Financial services | 2025 |
| Jones Pharma Services Ltd | Health & social care | 2019 |
| Jones Transport and Building Services Ltd | Transport & logistics | 2019 |
| Jongela CYF | Professional & scientific | 2024 |
| Jonny Matthew Ltd | Health & social care | 2024 |
| Joseph Thomas Property Services Ltd | Construction | 2025 |
| Josephine Swede Psychology Limited | Health & social care | 2024 |
| Joshffon Ltd | Hospitality | 2023 |
| Josquared Ltd | Real estate | 2024 |
| Josshua Limited | Wholesale & retail | 2025 |
| JP Developments & Construction Ltd | Construction | 2022 |
| JPE Car Sales Ltd | Wholesale & retail | 2023 |
| JPF Leisure Limited | Wholesale & retail | 2021 |
| JR & S Jones Rentals Ltd | Real estate | 2026 |
| JR Agencies Limited | Real estate | 2010 |
| JR Holdings Ltd | Real estate | 2024 |
| JR Plumbing & GAS Limited | Construction | 2017 |
| Jrdd Property Maintenance Limited | Administrative & support | 2024 |
| Jrdg Properties Limited | Real estate | 2026 |
| Jrf's Holdings Ltd | Real estate | 2025 |
| Jrw.Hair Ltd | Other services | 2023 |
| JSC Invest Ltd | Administrative & support | 2024 |
| JSH Developments Limited | Real estate | 2015 |
| JSM Legacy Ltd | Construction | 2024 |
| JST Engineering Group Ltd | Construction | 2026 |
| JT Bran Ltd | Manufacturing | 2025 |
| Jt's Motorcycles (Bridgend) Limited | Wholesale & retail | 2009 |
| Jt's Travel Ltd | Transport & logistics | 2020 |
| Jtucker Limited | Hospitality | 2025 |
| Julian & Elizabeth Ltd | Wholesale & retail | 2013 |
| Jumpcote Limited | Extraterritorial | 2026 |
| Jumpmead Limited | Wholesale & retail | 2025 |
| Jumpreed Limited | Extraterritorial | 2026 |
| Jumprise Limited | Extraterritorial | 2025 |
| Jungle Island Co Limited | Education | 2013 |
| Juno Bookkeeping and Accountancy Solutions Limited | Professional & scientific | 2013 |
| Just Drive (South Wales) Ltd | Wholesale & retail | 2017 |
| Just JDR Ltd | Transport & logistics | 2025 |
| Just the MAN Limited | Construction | 2021 |
| Just the MAN Supplies Limited | Wholesale & retail | 2025 |
| Justbray Limited | Extraterritorial | 2024 |
| Justin Lott Limited | Information & communication | 2023 |
| Justline Limited | Extraterritorial | 2026 |
| Justover Limited | Extraterritorial | 2025 |
| JW Morris Limited | Construction | 2018 |
| JYC Limited | Public administration | 2024 |
| K & a Holdings Limited | Professional & scientific | 2003 |
| K & E Roofing Ltd | Construction | 2021 |
| K and M Care Services Ltd | Health & social care | 2026 |
| K Gibbins Limited | Manufacturing | 2026 |
| K J Herbert (Finance) Limited | Financial services | 2013 |
| K R D Consultancy Limited | Public administration | 2018 |
| K-Form Exports Limited | Manufacturing | 2016 |
| K. J. Herbert (Insurance Services) Limited | Financial services | 1973 |
| K.N.M. Limited | Manufacturing | 1995 |
| K.N.M. Properties (Bridgend) Limited | Hospitality | 2012 |
| K.P. & SON Ltd | Mining & quarrying | 1999 |
| K.P. Bioplex Limited | Professional & scientific | 1980 |
| K16 Ltd | Hospitality | 2020 |
| K2 Motors Wales Limited | Wholesale & retail | 2017 |
| Kagey Ltd | Hospitality | 2007 |
| KAJ Leadership Ltd | Professional & scientific | 2024 |
| Kajoty Limited | Hospitality | 2011 |
| Kamath Dermatology Ltd | Health & social care | 2020 |
| Karikalan Limited | Wholesale & retail | 2020 |
| Karma Fitness and Agility Limited | Arts & recreation | 2023 |
| Karrie's Coffee Co Ltd | Hospitality | 2022 |
| Katharos LDN Ltd | Wholesale & retail | 2026 |
| KB Installations (Wales) Ltd | Construction | 2010 |
| KB Maintenance Ltd | Administrative & support | 2014 |
| KBS Crown Ltd | Construction | 2016 |
| KCH Properties Limited | Real estate | 2018 |
| KD Property Consultancy Ltd | Professional & scientific | 2023 |
| Keeffy’S Kicks Limited | Wholesale & retail | 2025 |
| Keeparch Limited | Extraterritorial | 2024 |
| Keepbeck Limited | Extraterritorial | 2025 |
| Keepdale Limited | Extraterritorial | 2025 |
| Keephart Limited | Construction | 2025 |
| Keepshaw Limited | Extraterritorial | 2026 |
| Keepward Limited | Extraterritorial | 2025 |
| Keith Evans Properties Ltd | Real estate | 2016 |
| Kellys Chippy Ltd | Hospitality | 2026 |
| Kelsan Transport Services Limited | Transport & logistics | 2007 |
| Kelsham Limited | Construction | 2004 |
| Keltic Fires UK Ltd | Wholesale & retail | 2015 |
| Kemolar Ltd | Hospitality | 2024 |
| KEN Thomas Associates Limited | Administrative & support | 2008 |
| Kendall Developments (Bridgend) Limited | Construction | 2008 |
| Kenfig Hill Barber Ltd | Other services | 2025 |
| Kenfig Hill RFC Limited | Arts & recreation | 2017 |
| Kenfig Nature Corporation Ltd | Real estate | 2020 |
| Kenfighil Superstore Ltd | Wholesale & retail | 2024 |
| Kentacre Limited | Wholesale & retail | 2024 |
| Kentback Limited | Extraterritorial | 2025 |
| Kentmay Limited | Extraterritorial | 2026 |