| KH Diamond Brickwork Ltd | Construction | 2023 |
| Khiz Car Private Ltd | Transport & logistics | 2016 |
| Kickstart Motorcycles Ltd | Wholesale & retail | 2019 |
| King Site Services (South West) Limited | Manufacturing | 1985 |
| Kingside Engineering Ltd | Manufacturing | 2025 |
| Kingside Holdings Limited | Manufacturing | 2024 |
| Kingstone Finance Group Ltd | Financial services | 2026 |
| Kitchenflow Limited | Hospitality | 2023 |
| KJP Design Limited | Professional & scientific | 2011 |
| Knockout Cafe Ltd | Hospitality | 2025 |
| Koda Cards Ltd | Wholesale & retail | 2022 |
| Korero Consulting Limited | Professional & scientific | 2007 |
| Krcw Ltd | Transport & logistics | 2025 |
| KRJ Carpentry Ltd | Construction | 2022 |
| Kumar Shops Limited | Wholesale & retail | 2020 |
| Kumars Investments Limited | Real estate | 2017 |
| Kye-Tec Security & K9 Ltd | Administrative & support | 2022 |
| KYLETHOMASBUSINESS87 Ltd | Transport & logistics | 2025 |
| L & a Stonework Limited | Construction | 2023 |
| L.A Event Catering Limited | Hospitality | 2025 |
| L.Camps Recovery Ltd | Transport & logistics | 2022 |
| Lady Landscapes Ltd | Administrative & support | 2024 |
| Lakeside Medical Limited | Health & social care | 2022 |
| Lakewell Utilities Limited | Construction | 2013 |
| Landscapes Unlimited UK Ltd | Construction | 2018 |
| Langland House Mariners Quay RTM Company Limited | Households | 2019 |
| Laser Profiling Limited | Manufacturing | 2023 |
| Lazy Lizard Labs Limited | Information & communication | 2009 |
| LCU Ltd | Construction | 2025 |
| Lean Asset Management Limited | Financial services | 2023 |
| Lean Pica Limited | Information & communication | 2014 |
| LEE Coombes GAS Services Ltd | Construction | 2024 |
| Lees Plant Operator Solutions Limited | Agriculture & fishing | 2017 |
| Leftfield Environmental Limited | Professional & scientific | 2010 |
| LEO Assemblies Limited | Manufacturing | 2006 |
| Let's Go Hire Ltd | Arts & recreation | 2026 |
| Let's Personalise IT Limited | Manufacturing | 2018 |
| LG Building Management Services Limited | Extraterritorial | 2009 |
| LGC Cosmetics Limited | Other services | 2024 |
| Liam Barness Engineering Limited | Professional & scientific | 2024 |
| Liam Morgan Ltd | Transport & logistics | 2025 |
| Libra Investment Property Group Limited | Professional & scientific | 2006 |
| Libra Investment Property Services Limited | Real estate | 2007 |
| Libra Investment Property Services RCT Limited | Construction | 2010 |
| Life Electric Ltd | Construction | 2026 |
| Life Property Group Ltd | Construction | 2019 |
| Life Property Land Ltd | Construction | 2024 |
| Lift 4 Less Limited | Administrative & support | 2005 |
| Lighthouse Estate Management Ltd | Real estate | 2023 |
| Lighthouse Residential Homes Ltd | Health & social care | 2021 |
| Lime Block Investments Ltd | Real estate | 2025 |
| Lindisfarne Films Limited | Information & communication | 2011 |
| Lineclaim Limited | Professional & scientific | 1989 |
| Linzheng Ltd | Hospitality | 2026 |
| Liri Jewellery Ltd | Manufacturing | 2020 |
| Little Miss Scribbles Ltd | Arts & recreation | 2007 |
| LJ Logistics Ltd | Transport & logistics | 2026 |
| LJC Management (South Wales) Limited | Other services | 2023 |
| LJH Timber Harvesting Ltd | Agriculture & fishing | 2024 |
| LK23 Ltd | Professional & scientific | 2026 |
| Llandeilo Road (Cross Hands) Ltd | Construction | 2013 |
| Llederw Ltd | Construction | 2016 |
| Lloyds Roofing Ltd. | Construction | 2026 |
| Llwyn Y Ffynnon Ltd | Agriculture & fishing | 2021 |
| Llynfi Construction & Plant Hire Ltd | Administrative & support | 2021 |
| LMG Home Improvements Limited | Construction | 2016 |
| Lmhse Services Limited | Professional & scientific | 2025 |
| LMK Supply Ltd | Wholesale & retail | 2025 |
| LMT Scaffolding Ltd | Construction | 2025 |
| Lnpkap Limited | Transport & logistics | 2025 |
| Lo-Chlor Chemicals Limited | Administrative & support | 2012 |
| LOC Plumbing and Heating Ltd | Construction | 2022 |
| LOC Waste Management Ltd | Water & waste | 2023 |
| Localsonly Ltd | Information & communication | 2025 |
| Logic Labs Limited | Information & communication | 2005 |
| Lomin Company Ltd | Wholesale & retail | 2022 |
| LOS Devitos Limited | Arts & recreation | 2019 |
| Lots of Tots Childcare Ltd | Health & social care | 2011 |
| Lrcx Consultants Limited | Information & communication | 2016 |
| Ltisw Limited | Health & social care | 2025 |
| Lubaw Limited | Health & social care | 2021 |
| Lumencore Synergy Ltd | Health & social care | 2025 |
| Lunacy Ltd | Wholesale & retail | 2007 |
| Luts Ltd | Transport & logistics | 2025 |
| LUX Biotech Limited | Professional & scientific | 2023 |
| LUX Enhancements Ltd | Other services | 2025 |
| LV Store Ltd | Wholesale & retail | 2022 |
| LW Community Services | Health & social care | 2015 |
| M & N Cleaning (Swansea) Ltd | Other services | 2021 |
| M a Frankcom Ltd | Construction | 2021 |
| M Clay Properties Limited | Real estate | 2016 |
| M J J Welding Services Ltd | Professional & scientific | 2024 |
| M Shahid Crop Limited | Wholesale & retail | 2025 |
| M&J Holdings and Investments Ltd | Financial services | 2024 |
| M&J Monolith Construction Ltd | Construction | 2024 |
| Mabe Construction Ltd | Construction | 2025 |
| Machineop Ltd | Administrative & support | 2024 |
| Mackworth Leisure Services Limited | Arts & recreation | 1994 |
| Maclennan Bros. International Limited | | 1976 |
| Madeleine Earl Chiropractic Limited | Health & social care | 2017 |