| John Thornberry Architecture Limited | Professional & scientific | 2018 |
| John Walpole Commercials Limited | Transport & logistics | 1973 |
| Johnson Steelfixing Limited | Construction | 2004 |
| Joinery CAD Solutions Limited | Construction | 2006 |
| Joining Technologies (Eastern) Limited | Wholesale & retail | 2002 |
| Jones Family Lettings Ltd | Real estate | 2024 |
| JRR Construction Limited | Construction | 2004 |
| JS (UK) Limited | Other services | 2004 |
| JSC Consulting Limited | Information & communication | 2003 |
| Just ASK Limited | Extraterritorial | 1972 |
| Just Cruize Limited | Transport & logistics | 2024 |
| Just for Groups Limited | Administrative & support | 2005 |
| JW (Norfolk) Ltd | Wholesale & retail | 1969 |
| K & K Excelsior Ltd | Construction | 2004 |
| K H Groundworks Ltd | Construction | 2006 |
| K R Fireplaces Limited | Construction | 2003 |
| K-Fix Limited | Wholesale & retail | 2002 |
| K. & R.C. Thompson Limited | | 1970 |
| K.J. Shortis Limited | Professional & scientific | 1971 |
| Kalni Foods T/A Indian Summer Restaurant Limited | Hospitality | 2017 |
| Karrelbrook House Property Management Company Limited | Households | 2006 |
| Kashfull Ltd | Hospitality | 2024 |
| Kayahan Limited | Hospitality | 2007 |
| Keeping-It-Hot Ltd | Construction | 2008 |
| Kelley Stone Park Limited | | 1984 |
| Kenneth Allison Limited | | 1980 |
| Kericole Limited | Construction | 1999 |
| Kerrys Flooring Limited | Wholesale & retail | 2007 |
| Kesgrave Chiropractic Clinic Ltd | Health & social care | 2005 |
| Ketteringham Hall Limited | Real estate | 2002 |
| Ketts News Service Limited | Information & communication | 2003 |
| Key Audio Visual Limited | Administrative & support | 2007 |
| Keyfix Systems Limited | Information & communication | 2000 |
| King's Lynn Auto Electrical Limited | Wholesale & retail | 1977 |
| King's Lynn Conservatories Limited | | 1988 |
| Kingdom Agriculture & Landscapes Limited | Administrative & support | 2003 |
| Kings Lynn Mini Mart Ltd | Wholesale & retail | 2020 |
| Kingsland Engineering Company Limited(The) | Manufacturing | 1983 |
| Kingwood House Stables Limited | Real estate | 1989 |
| KJR Consultancy Limited | Administrative & support | 2007 |
| KL Technologies Holdings Limited | Financial services | 2017 |
| KN Lighting Ltd | Information & communication | 2017 |
| Knapton Farming | | 1999 |
| KNEE3D Ltd | Professional & scientific | 2024 |
| Knicat Limited | Manufacturing | 1991 |
| Knight Accountancy Ltd | Professional & scientific | 2019 |
| KYC Asian Food Limited | Hospitality | 2025 |
| L & F Homes Ltd | Extraterritorial | 2008 |
| L F Papworth Limited | Agriculture & fishing | 2004 |
| L H Hayes and Sons Ltd | Construction | 2002 |
| L H Mechanical Handling Limited | Professional & scientific | 1961 |
| L S Groundwork and Civils Limited | Professional & scientific | 2005 |
| Ladbrook Engineering & Manufacturing Company Limited(The) | Administrative & support | 1942 |
| Ladbrook MFG Limited | Manufacturing | 2001 |
| Lakenham Creamery Limited | Manufacturing | 1992 |
| Lakers Games Ltd | Wholesale & retail | 2024 |
| Lakes Comps Ltd | Wholesale & retail | 2025 |
| Lanes Jewellery Limited | Wholesale & retail | 2003 |
| Langland Technical Services Ltd. | Information & communication | 2003 |
| Langley School (1960) Limited | Education | 1960 |
| Larner Brothers Limited | Professional & scientific | 1955 |
| Larrone Limited | | 1982 |
| LEE Finch Consultancy Limited | Professional & scientific | 2001 |
| Leonard Brittan & Co. Limited | Real estate | 1971 |
| Leonard Towler & Company Limited | Agriculture & fishing | 1952 |
| Leoshi Property Limited | Real estate | 2024 |
| Letton Farms Ltd. | Agriculture & fishing | 1989 |
| Lewis Redgrave Investments Limited | Real estate | 1987 |
| Lexham Utilities Limited | Administrative & support | 2010 |
| Liebenberg Limited | Health & social care | 2007 |
| Limitless Penguins Ltd | Wholesale & retail | 2024 |
| Linco PLC | Wholesale & retail | 1985 |
| Lincolnshire Driveways Limited | Administrative & support | 2024 |
| Linnets in the Community | Education | 2020 |
| Little Byte Ltd | Information & communication | 2025 |
| Logiclothes Limited | Wholesale & retail | 2004 |
| London and Edinburgh Insurance Company Limited | Extraterritorial | 1967 |
| Lucas + Western Architects Limited | Professional & scientific | 2018 |
| Lucky House Chinese Takeaway Ltd | Hospitality | 2024 |
| Lumill Property Limited | Construction | 1958 |
| Lusher Contracts Limited | Construction | 2007 |
| Luxuryfuture Limited | Real estate | 1995 |
| Lysias House Limited | Financial services | 2006 |
| M & K Kebabs Ltd | Hospitality | 2024 |
| M & L Plasterers Limited | Construction | 2004 |
| M & W Autos (Wisbech) Limited | Wholesale & retail | 2006 |
| M a Hanby Limited | Financial services | 2017 |
| M B Wakefield Electrical Limited | Construction | 2002 |
| M C Electrical (E.A.) Limited | Construction | 2006 |
| M E Roberts Limited | Professional & scientific | 2002 |
| M G Property Developments Limited | Real estate | 1999 |
| M S Shingles Ltd | Construction | 2002 |
| M Shaw Services Limited | Construction | 2005 |
| M T Daniels Limited | Manufacturing | 2013 |
| M&R Clothing Ltd | Wholesale & retail | 2025 |
| M. D. H. ARB Hire Limited | Administrative & support | 2007 |
| M.A.R. Installations Limited | Construction | 2005 |
| M.D. Blackburn Limited | Transport & logistics | 2005 |
| M.D.W. Trading Limited | Agriculture & fishing | 2002 |
| M.F.M. (Construction) Limited | Construction | 1981 |