| L.H. Snow & SON Limited | Construction | 1988 |
| L.P. GAS Limited | Energy | 2019 |
| L.P. GAS Wales Direct Limited | Energy | 1997 |
| L10N Go Ltd | Professional & scientific | 2019 |
| LA Creme Patisserie & Catering Co. Ltd | Manufacturing | 2005 |
| Laguna’S Best Ltd | Health & social care | 2023 |
| Laken Construction Ltd | Construction | 2025 |
| Laken Group Ltd | Construction | 2025 |
| Laker Bar and Maintenance Ltd | Construction | 2024 |
| Laker Electrical Services Ltd | Manufacturing | 2006 |
| Laksta Limited | Wholesale & retail | 2026 |
| Lamb & Flag Glynneath 2025 Ltd | Hospitality | 2025 |
| Lamps Glow Ltd | Construction | 2021 |
| Language Specialists (International) Limited | Real estate | 1984 |
| Lase Limited | Manufacturing | 2012 |
| Laser Surfacing Ltd | Professional & scientific | 2012 |
| Last Legs Ltd | Hospitality | 2022 |
| Lavamyz Limited | Real estate | 1999 |
| Lawr Y Grisiau Limited | Information & communication | 2022 |
| Ldeh Engineering Services Limited | Construction | 2025 |
| Ldeh Limited | Construction | 2022 |
| Leah's Whippy Limited | Hospitality | 2024 |
| Leanne Drane Ltd | Health & social care | 2021 |
| Leasem Limited | Hospitality | 2019 |
| Lee's Garden Neath Ltd | Hospitality | 2025 |
| Leicester House Glynneath Limited | Hospitality | 2026 |
| Lewis 4 X 4 (Neath) Ltd | Wholesale & retail | 2014 |
| Lewis Bespoke Vehicles Ltd | Wholesale & retail | 2019 |
| Lewis GAS & Electrical Ltd | Construction | 2026 |
| Lextan Limited | Other services | 2009 |
| LG Plumbing and Maintenance Ltd | Construction | 2021 |
| Liberty's Function Suite Ltd | Hospitality | 2012 |
| Licensed Trade Compliance Limited | Hospitality | 2015 |
| Lifeline Assist Ltd | Professional & scientific | 2011 |
| Lila Cleaning Services Ltd | Other services | 2018 |
| Lila Transport Ltd | Transport & logistics | 2017 |
| Lily Healthcare Remedy Limited | Health & social care | 2015 |
| Limbell Limited | Hospitality | 1997 |
| Limbu Plant Systems Limited | Wholesale & retail | 2025 |
| Lindum College (ATD) Limited | Other services | 2023 |
| Link IT OUT Limited | Wholesale & retail | 2023 |
| Linked Estates UK Limited | Water & waste | 2015 |
| Lions Legends Limited | Professional & scientific | 2021 |
| Litter Clear Ltd | Construction | 2015 |
| Little Ones Publishing Ltd | Other services | 2025 |
| LJ Thomas (DM) Ltd | Professional & scientific | 2021 |
| LJM AGA Servicing Ltd | Construction | 2022 |
| Llan Properties Ltd | Real estate | 2024 |
| Llandarcy Park Limited | Real estate | 1998 |
| Llandow Vale Estates Limited | Extraterritorial | 2007 |
| Llanelec Holdings Limited | Manufacturing | 2008 |
| Llanelec Precision Engineering Company Limited | Manufacturing | 1987 |
| Llanelec Topco Limited | Manufacturing | 2025 |
| Lloyd Consultancy Services Ltd | Extraterritorial | 2021 |
| LMC Holdings Ltd | Financial services | 2020 |
| Local Utility Store Limited | Wholesale & retail | 2012 |
| Local Vape Shop NO 1 Limited | Wholesale & retail | 2023 |
| Lodge Autos Direct Ltd | Wholesale & retail | 2025 |
| Lodge Van and Car Hire Limited | Administrative & support | 2016 |
| Logic Creations Limited | Information & communication | 2002 |
| Lonely Shepherd Productions Limited | Administrative & support | 2025 |
| Longrow Plant Hire (Pembroke) Limited | | 1987 |
| Loom and Living Ltd | Wholesale & retail | 2025 |
| Lovehuddle Ltd | Information & communication | 2026 |
| LPJ Civils & Groundworks Ltd | Construction | 2020 |
| LR Drywall Finishers Limited | Construction | 2023 |
| LRP Property Holdings Ltd | Real estate | 2024 |
| LS Neath Limited | Hospitality | 2023 |
| LT Deliveries Ltd | Transport & logistics | 2025 |
| LT10 Limited | Professional & scientific | 2026 |
| LTB Consulting Limited | Professional & scientific | 2025 |
| Lucky Corner 888 Ltd | Hospitality | 2023 |
| Lucrezia Properties Ltd | Real estate | 2022 |
| Luem Ltd | Professional & scientific | 2023 |
| Luff Logistics Ltd | Transport & logistics | 2025 |
| Luke Colwell Limited | Other services | 2024 |
| Lullaby Entertainment and Technical Services Limited | Arts & recreation | 2007 |
| Lush and Tidy Ltd | Wholesale & retail | 2020 |
| LV and Sons Properties Ltd | Real estate | 2026 |
| LV Plumbing & GAS Ltd | Construction | 2023 |
| M & a Powell Properties Limited | Real estate | 2024 |
| M and S Business Services Ltd | Administrative & support | 2019 |
| M Cuddy Group Limited | Financial services | 1960 |
| M D Blakeway Ltd | Real estate | 2018 |
| M G M Engineering Limited | Professional & scientific | 2019 |
| M L&D Living Ltd | Real estate | 2026 |
| M Mint Ltd | Hospitality | 2019 |
| M&R Flooring Limited | Construction | 2023 |
| M. Burley Consultants Ltd | Construction | 2013 |
| M.J.S. Manufacturing Limited | | 1983 |
| M4 Lifting Services Limited | Manufacturing | 2013 |
| M44 Hospitality Ltd | Hospitality | 2025 |
| Mace Interiors UK Limited | Manufacturing | 2002 |
| Maci Europe Limited | Real estate | 2015 |
| Macron Wales Retail Ltd | Administrative & support | 2020 |
| Macs Drinks Limited | Manufacturing | 2023 |
| Macs Foods Limited | Hospitality | 2019 |
| Macs Properties Ltd | Real estate | 2020 |
| Macwhirter Motorsport Limited | Manufacturing | 2016 |
| Madame Ferrari Ltd | Extraterritorial | 2021 |