| JMS Electrical Group Ltd | Construction | 2025 |
| JNA Shellfish Limited | Agriculture & fishing | 2013 |
| John Close & SON Limited | Agriculture & fishing | 1947 |
| John Fish Plumbing and Heating Ltd | Professional & scientific | 2012 |
| John Manners Limited | Wholesale & retail | 2005 |
| JSD Hotel (Berwick) Ltd | Hospitality | 2022 |
| Juno Energy Ltd | Professional & scientific | 2006 |
| Justfone Limited | Information & communication | 2000 |
| K Dixon Building Services Limited | Construction | 2013 |
| Kara Boska Ltd | Wholesale & retail | 2020 |
| Keith Hutton Engineering Limited | Manufacturing | 2012 |
| Kesim Food Catering Ltd | Hospitality | 2020 |
| Kids Racing Ltd | Wholesale & retail | 2011 |
| Kidstruction C.I.C. | Construction | 2025 |
| Kieran Bullen Limited | Professional & scientific | 2024 |
| Kiln Hill Pre-School Limited | Education | 2007 |
| King Group (ORD) Limited | Real estate | 2026 |
| Kittikhun Asset Management Ltd | Financial services | 2025 |
| Knickers and Moves Ltd | Real estate | 2023 |
| KSA Training Limited | Education | 2002 |
| L P Holborn Ltd | Manufacturing | 2019 |
| Lammermuir House Care Limited | Health & social care | 2025 |
| Landels Electrical (Berwick) Ltd | Construction | 2024 |
| Landels Electrical LLP | | 2010 |
| Langham Toll Kennels Limited | Other services | 2007 |
| Laroyle Ltd | Wholesale & retail | 2024 |
| Lattogroup Ltd | Financial services | 2025 |
| Lauderdale and Lothians Trust Limited | Professional & scientific | 1945 |
| LEE Garden Tweedmouth Ltd | Hospitality | 2024 |
| Leucopsis Limited | Financial services | 2012 |
| Lforl Limited | Arts & recreation | 2019 |
| Lhfp Ltd | Professional & scientific | 2011 |
| Liam Turton Ltd | Administrative & support | 2025 |
| Liamweb Ltd | Construction | 2026 |
| Lighthouse & Tweed Ltd | Hospitality | 2025 |
| Limencello Limited | Hospitality | 2017 |
| Lindisfarne Homes Limited | Construction | 2003 |
| Lindisfarne Leisure Limited | Hospitality | 2009 |
| Lindisfarne Luing Limited | Agriculture & fishing | 2010 |
| Lindisfarne Oysters Ltd | Agriculture & fishing | 2012 |
| Little Lamberton Ltd | Hospitality | 2020 |
| Little Poland Ltd | Wholesale & retail | 2013 |
| LJ Property Rental Ltd | Real estate | 2024 |
| Lodges and Caravans for Sale Limited | Information & communication | 2025 |
| Logike Limited | Professional & scientific | 1987 |
| London Premium Cars Limited | Transport & logistics | 2007 |
| London Premium Group Limited | Professional & scientific | 2008 |
| London Premium Holdings Limited | Professional & scientific | 2008 |
| Long Distance Removals Ltd | Transport & logistics | 2018 |
| Longridge Towers School | Education | 1982 |
| Lonsdale Rentals Limited | Real estate | 2025 |
| Love Lane (Tintagel House) Management Limited | Households | 1986 |
| Love Lane Mews Limited | Construction | 2007 |
| LOW Bleakhope Farm Limited | Agriculture & fishing | 2010 |
| Lowick Construction Limited | Construction | 2016 |
| Lowick Cottages Ltd | Hospitality | 2022 |
| Lowick Hall Estates Limited(The) | Agriculture & fishing | 1941 |
| Lsta Beyst Limited | Transport & logistics | 2025 |
| Lucker Country Park Limited | Hospitality | 2022 |
| Lucky PUP Prizes Limited | Arts & recreation | 2025 |
| Lunardi Court Care Limited | Health & social care | 2024 |
| LUX Nails and Spa 99 Limited | Other services | 2026 |
| Luxury Holiday Let's Ltd | Hospitality | 2024 |
| Maclean Eggs Ltd | Administrative & support | 2015 |
| Maclean Haulage Ltd | Transport & logistics | 2016 |
| Maden Eco Fuels Ltd | Wholesale & retail | 2013 |
| Maden Eco Ltd | Construction | 2012 |
| Maden Holdings Ltd | Professional & scientific | 2009 |
| Maden Property Assets Limited | Real estate | 2020 |
| Maden Property Developments (Cornhill RD) Ltd | Construction | 2018 |
| Maden Property Developments Ltd | Real estate | 2009 |
| Magna Tandoori Ltd | Hospitality | 2016 |
| Maines Farm Contracting Limited | Agriculture & fishing | 2012 |
| MAM Rural Limited | Real estate | 2019 |
| Mark Caudwell Limited | Agriculture & fishing | 1988 |
| Marriner Business Support Limited | Professional & scientific | 2009 |
| Marshall Leisure Limited | Real estate | 1960 |
| Marygate House Holy Island | Other services | 2012 |
| Mason Farm Machinery Ltd | Wholesale & retail | 2018 |
| Matosilva Ltd | Information & communication | 2016 |
| Mattwood Developments Ltd | Construction | 2013 |
| MAXPRONE2 Limited | Professional & scientific | 2019 |
| Mccall Capital Assets Ltd | Real estate | 2005 |
| Mccall Commercial Holdings Ltd | Real estate | 2008 |
| Mccall Residential Ltd | Real estate | 2021 |
| MCS Building Ltd | Extraterritorial | 2014 |
| Meadow Hill Developments Ltd | Real estate | 2021 |
| Medea Limited | Administrative & support | 1973 |
| MEG Maitland Ltd | Wholesale & retail | 2014 |
| Middleton Hall Cottages Management Company Ltd | Real estate | 2015 |
| Milanocafe Ltd | Hospitality | 2025 |
| MNM Rope Access Ltd | Construction | 2025 |
| Monad Software Ltd | Information & communication | 2011 |
| Moor & SON Limited | Agriculture & fishing | 2008 |
| Moorhouse Farm Coffee Shop Limited | Hospitality | 2005 |
| Morrison Community Care (Leamington Spa) Holdco Limited | Financial services | 2022 |
| Morrison Community Care (Leamington Spa) Propco Limited | Financial services | 2022 |
| Motion & Scale Ltd | Information & communication | 2026 |
| Mount Carmel Services Ltd | Households | 2008 |
| N.E. Numbers Limited | Administrative & support | 2003 |