| Kwl.Tom Ltd. | Ramsgate | 2019 |
| KWN Marine Limited | Stonehaven | 2004 |
| Kyle Rose Services Limited | Aberdeen | 2025 |
| Kylerin Consultancy Services Limited | Crieff | 2018 |
| Kyol Ltd | Stornoway | 2024 |
| L & JM Ltd | Inverurie | 2013 |
| L & L Services Ltd | Great Yarmouth | 2016 |
| L & R Wall Ltd | Ashington | 2015 |
| L Beastall Ltd | Lincoln | 2024 |
| L Brown Slickline Services Ltd | Norwich | 2023 |
| L Dodds Bolting Services Ltd | Ashington | 2024 |
| L Donald Ltd | Glasgow | 2019 |
| L Godfrey Pipe Technician Ltd | Whitley Bay | 2021 |
| L Hindson Ltd | Ashington | 2018 |
| L J S Access Services Ltd | South Shields | 2023 |
| L L Macvie & Co Ltd | Kelso | 2021 |
| L P Pallett Quarry (Feltwell) Ltd | Hertford | 2016 |
| L P Pallett Quarry (Henham) Limited | Hertford | 2014 |
| L Raffan Access Ltd | Dundee | 2022 |
| L&A Materials Management Limited | Twickenham | 2019 |
| L. P. Pallett Quarry Limited | Hertford | 2011 |
| L.B. Silica Sand Limited | Bedford | 1966 |
| L.S.E.H. Projects Limited | Clydebank | 2023 |
| L.W Pipework Systems Ltd | South Shields | 2015 |
| Labtos Charcoal Merchant Limited | Grays | 2017 |
| LAC Minerals Limited | London | 2021 |
| LAD on Rope Ltd | Spennymoor | 2019 |
| Lagan 106 Limited | Belfast | 1976 |
| Lagan Construction Services Limited | Belfast | 1975 |
| Lagan Land Restoration Company Ltd | Keady | 2023 |
| Laing Engineering Solutions Ltd | Falkirk | 2025 |
| Laird Aggregates Limited | Lunanhead, Forfar | 1964 |
| Laird Inspection Limited | Isle Of Lewis | 2011 |
| Lake Chandler HPA Limited | London | 2021 |
| Lake District Granite Limited | Chorley | 2022 |
| Lakel Gateway Limited | London | 2013 |
| Lakel Group Limited | London | 2005 |
| Lakeland Carbons Limited | Penrith | 1991 |
| Lakeland Green Slate & Stone Company Limited | Cumbria | 1957 |
| Lamasafety Ltd | Peterhead | 2019 |
| Lambent Global Limited | Colchester | 2023 |
| Lamtek Services Ltd | Liverpool | 2024 |
| Lancara Ltd | London | 2017 |
| Lance Johnson Ltd | Great Yarmouth | 2012 |
| Lancia Limited | Harrogate | 2011 |
| Land & Marine Piling and Consultancy Services Ltd. | Great Yarmouth | 2017 |
| Land Recovery Limited | Coalville | 1982 |
| Land Turn Trading Company | Hants | 1988 |
| Landfill File Ltd | London | 2025 |
| Landsker Limited | Swansea | 2004 |
| Lane Ters (UK) Pastoral Agriculture Technology Group Co., Ltd | Cardiff | 2024 |
| Langfang Eryue Business Co., Limited | Manchester | 2020 |
| Langside Quarry Limited | Lochgelly | 2023 |
| Langstone Energy Limited | London | 2017 |
| Lansdowne Celtic Sea Limited | London | 2005 |
| Lansdowne Resources PLC | London | 2005 |
| Lanue OIL & GAS Limited | London | 2017 |
| Lanvic Technical Consultancy Ltd | Aberdeen | 2019 |
| Larenim Ltd | Carmarthen | 2026 |
| Large Diameter Drilling Limited | Norwich | 2007 |
| Lark Electrical Services Ltd | Blackpool | 2008 |
| Lartehra Limited | London | 2017 |
| LAS Equipment Ltd | Diss | 2019 |
| Lasco Services Ltd | Forfar | 2019 |
| Latam Strategies Ltd | Newcastle Upon Tyne | 2011 |
| Laubex Fabrications Ltd | Tain | 2025 |
| Laven Engineering Limited | Horsham | 2006 |
| Lavendon Aggregates Limited | Welwyn Garden City | 2024 |
| Lawer Brothers Limited | Penryn | 1961 |
| Laws Geophysics Limited | Sheffield | 2011 |
| Laws Grab Services Ltd | Bexhill-On-Sea | 2025 |
| Laymax Procurement Ltd | Westhill | 2023 |
| LBW Machines Ltd | Tamworth | 2011 |
| LC Rope Access & Fabrication Ltd | Lowestoft | 2026 |
| LC Subsea Limited | Aberdeen | 2010 |
| LCI Services Ltd | Blackpool | 2019 |
| Lckr Ltd | Glasgow | 2018 |
| LCM Energy Limited | Aylesford | 2019 |
| LD Aggregates Ltd | | 2009 |
| LDH Pipeline Services Ltd | Ebbw Vale | 2026 |
| LDL Aggregates Ltd | Cookstown | 2011 |
| LDM Engineering Ltd | Newcastle Upon Tyne | 2014 |
| LDW Pipeline & Process Testing Limited | Mirfield | 2016 |
| LEA Marston Minerals & Recovery Limited | Burton On Trent | 2023 |
| Leapers Rock Ltd | Lancaster | 2016 |
| Leathan Mhuir Solutions Ltd | Fraserburgh | 2024 |
| Leather Energy Services Ltd | Dumfries | 2019 |
| LEE & Laura Caldwell Contractors Limited | Lowestoft | 2017 |
| LEE Evans Services Limited | Portree | 2022 |
| LEE Mckay Limited | Ellon | 2022 |
| LEE Rutherford Commissioning Services Limited | Hartlepool | 2013 |
| LEE Woodley (Blackpool) Ltd | Poulton-Le-Fylde | 2011 |
| Leer Quarries Limited | County Armagh | 2003 |
| Leese Consulting Ltd | Chipping Campden | 2019 |
| Leestone Sand & Gravel Limited | Co Down | 2003 |
| Leesum Utilities Ltd | Paisley | 2022 |
| Legacy Hill Resources Ltd | Bristol | 2014 |
| Leigh Harris Limited | Swansea | 2017 |
| Leilac Limited | Salisbury | 2009 |
| Leitch Project Control Services Limited | Stonehaven | 2013 |