| Jon’S Supplements Limited | Wholesale & retail | 2022 |
| Jordan's Construction Services Ltd | Administrative & support | 2019 |
| JP Collective Ltd | Professional & scientific | 2026 |
| Jpfb Properties Limited | Real estate | 2024 |
| JR Digital Media Ltd | Wholesale & retail | 2021 |
| Jrad Ltd | Construction | 2023 |
| JRM Rail Ltd | Construction | 2015 |
| JRT Trading Llanelli Limited | Water & waste | 2016 |
| JT Auto Traders Ltd | Wholesale & retail | 2025 |
| Juga Empires Ltd | Real estate | 2022 |
| Jumbo Supplies Limited | Administrative & support | 2021 |
| Just Financial Services (Wales) Ltd | Financial services | 2007 |
| Just Financial Services Limited | Extraterritorial | 2019 |
| Just Lime Limited | Construction | 2014 |
| Just Print Digital Ltd | Manufacturing | 2009 |
| K & K Energy Group Ltd | Wholesale & retail | 2026 |
| K P Autocentre Limited | Wholesale & retail | 2023 |
| K P Tyres Limited | Wholesale & retail | 2023 |
| K W Thomas & Co Limited | Financial services | 2020 |
| K&J Spice (Llanelli) Ltd | Hospitality | 2016 |
| K2K Trading Ltd | Wholesale & retail | 2025 |
| Kadija Properties Ltd | Real estate | 2024 |
| Karen Louisa Hardy Limited | Extraterritorial | 2024 |
| Karlie’S Cookout Limited | Hospitality | 2024 |
| KCS Scaffolding Ltd | Construction | 2025 |
| KD 5 Star Holidays Limited | Real estate | 2017 |
| KD Accounting Limited | Professional & scientific | 2015 |
| KD Saundersfoot Properties Limited | Hospitality | 2022 |
| KEL Tang Ltd | Real estate | 2024 |
| Kemeny Music and Drama Ltd | Arts & recreation | 2022 |
| Kerry Browne Limited | Hospitality | 2026 |
| Kest Property Developments Ltd | Real estate | 2024 |
| Khairan Express Ltd | Hospitality | 2026 |
| Khan Healthcare Ltd | Health & social care | 2022 |
| Khepri Wildlife Services and Consulting Ltd. | Professional & scientific | 2014 |
| Kiki's Hope for Animals CIC | Other services | 2023 |
| Kingston Closers Ltd | Professional & scientific | 2025 |
| Kirsty Williams Mortgage Solutions Ltd | Professional & scientific | 2023 |
| Kirsty's Law Ltd | Professional & scientific | 2022 |
| Kiss Storage Limited | Administrative & support | 2020 |
| Kiwb Ltd | Extraterritorial | 2020 |
| KLP Leisure Ltd | Hospitality | 2019 |
| Klunk and Dobby Ltd | Hospitality | 2025 |
| KMB Service Centre Limited | Wholesale & retail | 2016 |
| KN Richards Limited | Wholesale & retail | 2008 |
| Knabrock Ltd | Professional & scientific | 2023 |
| Knas Properties Limited | Real estate | 2021 |
| Knotweed Support - Invasive Weed Specialists Ltd | Administrative & support | 2016 |
| Kolay Para Contractors Ltd | Construction | 2020 |
| Kolay Para Properties Ltd | Real estate | 2020 |
| KPF Group Ltd | Construction | 2026 |
| Kraken Gaming Ltd | Wholesale & retail | 2022 |
| KRK Properties Ltd | Hospitality | 2012 |
| KSA Gold Ltd | Hospitality | 2019 |
| KSM Technology Ltd | Manufacturing | 2024 |
| Ksnr Lettings Limited | Real estate | 2018 |
| Kung FU Inn Limited | Hospitality | 2024 |
| Kuro HYO Ltd | Other services | 2024 |
| Kuroi RYU Limited | Other services | 2019 |
| KWM Recycling Ltd | Water & waste | 2023 |
| L & E Cambrey Ltd | Financial services | 2025 |
| L & I Motors Limited | Real estate | 1982 |
| L and C Rotating Solutions Ltd | Professional & scientific | 2026 |
| L J Taffetsauffer Wealth Management Limited | Financial services | 2017 |
| L&L Models Ltd | Wholesale & retail | 2017 |
| L. Weston Construction Ltd | Construction | 2025 |
| L.L. Carpentry Ltd | Construction | 2019 |
| L.P Care Solutions Ltd | Wholesale & retail | 2013 |
| L4TCH Ltd | Construction | 2019 |
| LA CHA CHA Productions Ltd | Information & communication | 2020 |
| Ladies Group Tours Ltd | Administrative & support | 2025 |
| Ladies WHO Travel Ltd | Administrative & support | 2024 |
| LAN Amdani Limited | Professional & scientific | 2026 |
| Lancehawk EOT Trustee Limited | Professional & scientific | 2021 |
| Landfill Services (South Wales) Limited | Construction | 1993 |
| Larkhill Enterprises Limited | Wholesale & retail | 2006 |
| Lashed by Lauren King Ltd | Other services | 2022 |
| Laugharne Limited | Professional & scientific | 2006 |
| Lavender Homes & Property Developments Limited | Construction | 2020 |
| Lawadvise Limited | Financial services | 2025 |
| Lazarus Transformation Ltd | Professional & scientific | 2023 |
| Lchd Homes Ltd | Real estate | 2025 |
| Lcld Properties Ltd | Real estate | 2023 |
| LD Eco Ltd | Manufacturing | 2013 |
| LD Eco Properties Ltd | Real estate | 2024 |
| LE Bras @ Rubys Ltd | Hospitality | 2022 |
| Leading the Way UK Ltd | Arts & recreation | 2022 |
| Lean Bites Ltd | Hospitality | 2021 |
| Learn ALL About Property Ltd | Education | 2021 |
| Learning Pack Limited | Information & communication | 1991 |
| Learning Partnership (Wales) Ltd | Education | 2007 |
| LEE Davies Property Ltd | Real estate | 2023 |
| Legally Ginger Ltd | Administrative & support | 2021 |
| Leira Limited | Professional & scientific | 2023 |
| Lewfield Mechanical Ltd | Construction | 2020 |
| Lewis Construction Building Contractors Wales Ltd | Construction | 2009 |
| Lewis Quality Solutions Limited | Manufacturing | 2024 |
| Lh&Ew Ltd | Hospitality | 2023 |
| Life Holdings Limited | Administrative & support | 2021 |
| Life Vitality Ltd | Professional & scientific | 2024 |