| Leith Power and Lighting Ltd | Thornton Cleveleys | 2013 |
| Leiths (Scotland) Limited | Aberdeen | 1977 |
| LEM Mining & Restoration Ltd. | Lancashire | 1997 |
| Lemuel Engineering Ltd | Leigh | 2023 |
| Leon Trading UK Ltd | London | 2020 |
| Leone Diamonds Limited | London | 2019 |
| Leotes Ltd | Hove | 2025 |
| Leroc Drilling Ltd | Motherwell | 2024 |
| LES Energy Services Limited | Guisborough | 2025 |
| Letson Securities Limited | London | 2011 |
| Leviathan Asset Integrity Ltd | Inverness | 2023 |
| Lewedin Group Limited | Uxbridge | 2024 |
| Lewis Macleod Quality Services Ltd | Turriff | 2025 |
| Lewis Quarries Ltd | Yeovil | 2016 |
| Lexiebab Technical Services Limited | London | 2024 |
| Lexon Energy UK Ltd | Dagenham | 2024 |
| Leyline Surveys Limited | Leamington Spa | 2017 |
| Leytonstone Services Limited | London | 1997 |
| LH Vulcanising Ltd | Stafford | 2025 |
| LHK Quarry Services Limited | Ulverston | 2015 |
| Liam Wilson Construction & Haulage Ltd | Borwick | 2025 |
| Liba Management and Investments Inc. Limited | London | 2017 |
| Liberty Resources Consulting Ltd | Aberdeen | 2024 |
| Licrown Ltd | Cardiff | 2025 |
| Life Light Energy Limited | Edinburgh | 2017 |
| Liftspec Ltd | Aberdeen | 2022 |
| Light UP Africa Ltd | Colchester | 2025 |
| Lightfab Ltd | Glasgow | 2021 |
| Lighthouse 783 Ltd | St. Andrews | 2023 |
| Lightspeed Arctic Ltd | Bristol | 2018 |
| Lightwater Quarries Limited | Ripon | 1976 |
| Lilac Arizaro UK Ltd | London | 2023 |
| Lilac Jaguar UK Ltd | London | 2024 |
| Lilac Services Argentina UK Ltd | London | 2023 |
| Lilac Tolar UK Ltd | London | 2023 |
| Lilatech Services Ltd | Dundee | 2018 |
| Limar OIL Tools (UK) Limited | Norwich | 2009 |
| Limehillock Ltd | Paisley | 2022 |
| Limehillock Quarries Ltd. | | 2005 |
| Linas Technical Services Ltd | Aberlour | 2026 |
| Lincoln W Ltd | Cardiff | 2016 |
| Lindrick Aggregates Limited | Sheffield | 2019 |
| Lindsay Davis Ltd | Kilbirnie | 2012 |
| Lindsay Gordon Millington Ltd | Ellesmere Port | 2018 |
| Lindsay Mccracken Ltd | Montrose | 2021 |
| Linganbo Engineering Limited | Banff | 1998 |
| Lingdale Engineering Limited | Saltburn-By-The-Sea | 1999 |
| Linnhe Plant Limited | Invernesshire | 1991 |
| Lion Mining Finance Limited | London | 1986 |
| Lion ORE Ltd | Weybridge | 2017 |
| Lionshead Consultants Limited | London | 2011 |
| Lisburn Enviro-Care Limited | Craigavon | 2007 |
| Lisowen Contracts Limited | Saintfield | 2016 |
| Lister Trading Corporation U.K Limited | London | 2008 |
| Lithium West Limited | Birmingham | 2023 |
| Lithixo Capital Limited | Birmingham | 2026 |
| Lithosight Ltd | Fareham | 2024 |
| Lithothermal Resources Ltd | Yarm | 2023 |
| Liverpool Music Village Ltd | Bangor | 2006 |
| Liverpool Quarry Ltd | Liverpool | 2019 |
| Livi Projects Ltd. | Livingston | 2011 |
| Living Neptune Services Limited | Norwich | 2017 |
| Lj.Griffin Ltd | Preston | 2023 |
| Ljar Aggregates Limited | Doncaster | 2022 |
| LJD Rope Access Ltd | Southampton | 2024 |
| LJS Offshore Electrical Services Limited | Blackpool | 2013 |
| LKS Technical Solutions Ltd | Inverness | 2012 |
| Llamas and Bannister Energy Advisors Ltd | London | 2021 |
| Llanelli Sand Dredging Limited | Fareham | 1938 |
| Llangorse Quarry Ltd | Bwlch | 2021 |
| Llechi Slate Evolution CYF | Caernarfon | 2021 |
| LLO Consulting Limited | Birmingham | 2025 |
| LLO Services Limited | Birmingham | 2021 |
| Lloyd's Register Aligned Services Limited | Aberdeen | 2007 |
| Lloyd's Register Finance Limited | Aberdeen | 2007 |
| Lloydie Contracting Limited | Church Stretton | 2017 |
| Lloyds Capital Ltd | Glasgow | 2018 |
| Llsn Ltd | Broughty Ferry | 2026 |
| Llynclys Aggregates Ltd | Coventry | 2021 |
| LMB Integrity Ltd | London | 2026 |
| LMG Consultants Ltd | Aberdeen | 2018 |
| LMJ Access & Coatings Ltd | Elgin | 2019 |
| Lnenergy Limited | London | 2021 |
| LOA Consultants Ltd | Shepperton | 2015 |
| Loch Ness Mechanical Services Ltd | Inverness | 2021 |
| Loch TAY Holdings Ltd | London | 2021 |
| Lochaline Quartz Sand Limited | Ormskirk | 2011 |
| Locharbriggs Sandstone Limited | Falkirk | 1998 |
| Lochinvar Coal Limited | London | 2012 |
| Loftingh.Nl Ltd | Bradwell | 2014 |
| Logging Ltd | Liverpool | 2025 |
| Logtech International Co., Ltd | Beckenham | 2015 |
| LOK Well Services Ltd | Montrose | 2006 |
| LOM Materials Limited | Belfast | 2011 |
| Lomond Offshore Services Ltd | Stirlingshire | 2004 |
| London & Paris Energy Limited | Milton Keynes | 2017 |
| London Africa Limited | Copthorne | 2020 |
| London Investment and Mining Green-Slate-Group (UK) Ltd | London | 2016 |
| London Maputo Energy Ltd | London | 2025 |
| London Mineral Resources Ltd | Mitcham | 2023 |