| LC Couriers Ltd | Transport & logistics | 2025 |
| LC Payment Services Limited | Professional & scientific | 2024 |
| LC Properties Limited | Real estate | 2002 |
| LCT Surfacing Ltd | Construction | 2023 |
| LDS Property Holdings Ltd | Real estate | 2019 |
| Leaning Tower of Pizza Limited | Hospitality | 2017 |
| Learnaboutfilm Ltd | Education | 2012 |
| Ledgeriq Ltd | Information & communication | 2019 |
| Leggett DJO Ltd | Transport & logistics | 2026 |
| Leverage Gym Equipment Ltd | Wholesale & retail | 2026 |
| Lewis Chaney Limited | Manufacturing | 2013 |
| Lexagor Limited | Professional & scientific | 2022 |
| Lexington IT Ltd | Information & communication | 2009 |
| LGC Developments Limited | Real estate | 2024 |
| Life of Reilly Coffee Ltd | Manufacturing | 2023 |
| Lighthouse Development Consulting Limited | Professional & scientific | 2021 |
| Lily in Bloom Therapy Ltd | Health & social care | 2026 |
| Lime Commercial Finance Limited | Financial services | 2020 |
| Lime Wealth Limited | Financial services | 2023 |
| Linc Telecom Limited | Wholesale & retail | 2020 |
| Lindens Penarth Limited | Households | 2001 |
| Liris Technologies Ltd | Administrative & support | 2024 |
| Little Dinosaur Limited | Information & communication | 2014 |
| Little Fizz and Party Fizz Franchise Ltd | Education | 2023 |
| Little Fizz CIC | Education | 2026 |
| Little FOX Design Ltd | Wholesale & retail | 2024 |
| Little Giant Media Ltd | Professional & scientific | 2014 |
| Little Often Always Ltd | Wholesale & retail | 2022 |
| Livfit London Ltd | Arts & recreation | 2023 |
| LJ Clarke Consulting Ltd | Professional & scientific | 2021 |
| LJ Construction UK Group Limited | Construction | 2025 |
| LJ Williams Group Ltd | Hospitality | 2026 |
| LJC Investments and Holdings Ltd | Real estate | 2020 |
| LJE Cardiff Construction Limited | Construction | 2020 |
| LJE Construction Swansea Limited | Construction | 2022 |
| LJL Management Limited | Real estate | 2017 |
| LJL Trading Limited | Hospitality | 2026 |
| Llandough Medical Services Limited | Health & social care | 2017 |
| Llewellyn Roofing & Solar Limited | Construction | 2024 |
| LLJ Hair and Make-Up Artist Ltd | Arts & recreation | 2021 |
| Llwyd Jones Ltd | Professional & scientific | 2022 |
| Location 7 Limited | Real estate | 2023 |
| Locker Room Events Ltd | Administrative & support | 2023 |
| Locks Court Management Company Limited | Households | 2008 |
| Lotus Properties (Wales) Limited | Real estate | 2015 |
| Lsmr Ltd | Real estate | 2025 |
| LT Property Developments Limited | Construction | 2016 |
| LTS Addy Property Ltd | Real estate | 2021 |
| Lucci HUT22 Company Ltd | Health & social care | 2026 |
| Lucid Theatre Ltd. | Arts & recreation | 2014 |
| Ludlow Street Properties Limited | Real estate | 2017 |
| Ludlow Street Services Limited | Financial services | 2019 |
| Luna 3D Products Ltd | Manufacturing | 2026 |
| LUX Watches Ltd | Wholesale & retail | 2019 |
| Luxtons Limited | Extraterritorial | 2001 |
| LVN Watches Ltd | Wholesale & retail | 2025 |
| Lynrad Capital Ltd | Real estate | 2025 |
| M Hope Holdings Ltd | Financial services | 2023 |
| M J Palmer Transport Ltd | Transport & logistics | 2021 |
| M Murphy Group Limited | Construction | 2018 |
| M S Cardiff Ltd | Hospitality | 2026 |
| M&K James Holdings Ltd | Financial services | 2023 |
| Mabinogi Productions Ltd | Administrative & support | 2015 |
| MAC Artists Ltd | Wholesale & retail | 2017 |
| MAC Tools Cardiff Limited | Wholesale & retail | 2018 |
| Macauley Automotive Ltd | Wholesale & retail | 2025 |
| Mack Events Presents Ltd | Arts & recreation | 2014 |
| Macob Scaffolding Contracts Limited | Construction | 1988 |
| Macroactive UK Limited | Professional & scientific | 2021 |
| Made by Moon Ltd | Information & communication | 2012 |
| Madhu's Hospitality Ltd | Hospitality | 2023 |
| Madison Securities Ltd | Real estate | 2020 |
| Magic Wand PR Limited | Professional & scientific | 2015 |
| Magnacell Ltd | Wholesale & retail | 2020 |
| Magnetic Metals Ltd | Wholesale & retail | 2019 |
| Maha Fish Bar Ltd | Hospitality | 2025 |
| Mainurgent Limited | | 1988 |
| MAK Communications Consultancy Limited | Information & communication | 2012 |
| Make Land CYF | Wholesale & retail | 2018 |
| Mallory Custom Lighting Limited | Wholesale & retail | 2023 |
| Mango Lettings Ltd | Real estate | 2019 |
| Marconi Holiday Villages Limited | Hospitality | 1961 |
| Marcus Howells Flooring Services Ltd | Construction | 2013 |
| Marine Court Residents Association Limited | Real estate | 1986 |
| Mariners Heights Limited | Households | 1987 |
| Market Bull Bar Ltd | Hospitality | 2026 |
| Marshall Development Group Ltd | Construction | 2026 |
| Martin Tinney Gallery Limited | Wholesale & retail | 1994 |
| Mast Tech Global Ltd | Information & communication | 2023 |
| Mathos Tutors Ltd | Education | 2026 |
| Mato Data Solutions Limited | Professional & scientific | 2025 |
| Matt Navarra Media Ltd | Professional & scientific | 2018 |
| Matt PG Morgan Limited | Information & communication | 2017 |
| Mawr Ltd | Information & communication | 2018 |
| Mayfair Stores Limited | Wholesale & retail | 2020 |
| Mbcco Ltd | Professional & scientific | 2025 |
| MCC Travel Ltd | Hospitality | 2024 |
| Mckenziecomps Ltd | Arts & recreation | 2026 |
| Mckinney Advisory Limited | Information & communication | 2024 |
| ME DE YA K9 Ltd | Professional & scientific | 2024 |