| LE & LE Properties Limited | Real estate | 2021 |
| LE Mode Limited | Other services | 2023 |
| Leadfab Limited | Manufacturing | 2021 |
| Leading Edge Consultancy Limited | Professional & scientific | 2015 |
| Leading Lignt Limited | Construction | 2025 |
| Learn VIA Saints Community Interest Company | Education | 2021 |
| Ledapt Limited | Wholesale & retail | 2020 |
| Legal Resourcing Limited | Other services | 2024 |
| Leigh Property Enterprises Ltd | Real estate | 2023 |
| Leighton Norris Saddlery Ltd | Other services | 2023 |
| Leisure Solutions (U.K.) Ltd. | Manufacturing | 2003 |
| Lemontree Property Management Ltd | Households | 2020 |
| LES Barbershop Ltd | Other services | 2022 |
| Letties Autos Ltd | Wholesale & retail | 2024 |
| Leviathan Supplies Ltd | Agriculture & fishing | 2020 |
| Liability Claims Investigations Ltd | Administrative & support | 2024 |
| Liannas Takeaway Ltd | Hospitality | 2025 |
| Libwy Ltd | Professional & scientific | 2021 |
| Life Through the Lens (South Wales) Ltd | Professional & scientific | 2023 |
| Lighthouse Company (PVT) Limited | Health & social care | 2023 |
| Lili-Mi Enterprises Ltd | Wholesale & retail | 2025 |
| Line Caught Bass Ltd | Agriculture & fishing | 2025 |
| Linea Executive Search Limited | Administrative & support | 2015 |
| Linkter Ltd | Information & communication | 2026 |
| Lion Group (Cardiff) Limited(The) | Professional & scientific | 1986 |
| Lion Industries (Cardiff) Limited | Professional & scientific | 1973 |
| Lion Laboratories Limited | Manufacturing | 1981 |
| Lion Scientific Limited | Professional & scientific | 1981 |
| Lion Technology Limited | Professional & scientific | 1979 |
| Lisette Saunders Consulting Ltd | Public administration | 2025 |
| Lite Year Media Ltd | Professional & scientific | 2020 |
| Little Dino Limited | Information & communication | 2025 |
| Little Legends Playhub Ltd | Health & social care | 2025 |
| Little Lions Athletics CIC | Arts & recreation | 2019 |
| Little Rainbow Play Ltd | Arts & recreation | 2025 |
| Little Space Cadets Ltd. | Health & social care | 2021 |
| Lixie Limited | Hospitality | 2018 |
| LIZ Hawrylak Ltd | Other services | 2022 |
| LJ Capital Ltd | Real estate | 2024 |
| LJ Travel Barry Ltd | Transport & logistics | 2023 |
| LJH RIG Ltd | Information & communication | 2026 |
| LJZ Cleaning Services Ltd | Administrative & support | 2024 |
| Lkbw Ltd | Health & social care | 2011 |
| Lloydstone Limited | Other services | 2014 |
| Lloyson Limited | Wholesale & retail | 2020 |
| LLR Carpentry Ltd | Construction | 2016 |
| LMF Motor Factors Ltd | Wholesale & retail | 2019 |
| Lmprestigemotors Ltd | Wholesale & retail | 2024 |
| Local Property Management Ltd | Real estate | 2025 |
| Locality Solutions Ltd | Information & communication | 2011 |
| Location Services (Wales) Limited | Information & communication | 2011 |
| Logistical Trading (Wales) Limited | Construction | 2015 |
| Lombard Grange Management Company Limited | Households | 1995 |
| Lorax (Trustee) Limited | Other services | 2020 |
| Lorax Limited | Wholesale & retail | 2005 |
| Losoma Properties Limited | Real estate | 2023 |
| Lost and Found Gaming CIC | Education | 2023 |
| Lovine Care Limited | Health & social care | 2020 |
| Loving Heart Ltd | Health & social care | 2018 |
| Lsjgrub Limited | Hospitality | 2025 |
| LT Electrical Engineering Ltd | Construction | 2025 |
| LT Scaffold Services Limited | Construction | 2016 |
| LT Scaffold Services Trustee Limited | Professional & scientific | 2024 |
| Luciano Evangelista Window Cleaning Services Ltd | Administrative & support | 2010 |
| LUCY2BELLS Limited | Hospitality | 2025 |
| Lumivo Light Ltd | Manufacturing | 2026 |
| Luna Tides Productions Ltd | Professional & scientific | 2023 |
| Lunch at Mine Ltd | Hospitality | 2025 |
| Lush Homes 4 U Ltd | Real estate | 2017 |
| Luxefield Property Care Ltd | Households | 2025 |
| LVD Property Investments Ltd | Real estate | 2026 |
| LYD FE Ltd | Hospitality | 2022 |
| Lyesniko Ltd | Hospitality | 2019 |
| M Canton Limited | Hospitality | 2014 |
| M E Rentals LLP | | 2017 |
| M Group Investments Ltd | Real estate | 2024 |
| M Group Properties Ltd | Real estate | 2024 |
| M&H (Barry) Ltd | Wholesale & retail | 2025 |
| M&T Electrical Services Ltd | Construction | 2019 |
| M.A.Hardy Limited | Agriculture & fishing | 1963 |
| Mabel 24 Limited | Hospitality | 2024 |
| Mabel Enterprises Limited | Real estate | 2022 |
| Mack International Trade Ltd | Wholesale & retail | 2017 |
| Mack Worx Limited | Administrative & support | 2026 |
| Madetop Limited | Real estate | 1983 |
| MAE Maria Limited | Hospitality | 2017 |
| Maeth Ltd | Information & communication | 2026 |
| Magbox Ltd | Information & communication | 2018 |
| Magbox Publishing Ltd | Information & communication | 2026 |
| Maher Consultants Ltd | Real estate | 2008 |
| Mahi Spice Limited | Hospitality | 2021 |
| Mahon Management Limited | Health & social care | 2012 |
| Main Street Motors Ltd | Wholesale & retail | 2022 |
| Mais Nails Ltd | Other services | 2024 |
| Makadara Enterprise Ltd | Transport & logistics | 2026 |
| Malarville & Co Ltd | Wholesale & retail | 2019 |
| Malfatti Estates Limited | Real estate | 2025 |
| Manalos Pizza & Grill Ltd | Hospitality | 2023 |
| Mandy Property Developments Ltd | Construction | 2022 |
| Mangoed Limited | Professional & scientific | 2014 |