| J.W. Needham Limited | Agriculture & fishing | 1953 |
| Jack Maxwell Limited | Real estate | 2018 |
| Jack's Tack Ltd | Wholesale & retail | 2026 |
| Jackson Wilde Ltd | Extraterritorial | 2018 |
| James Court (Louth) Management Company Limited | Households | 1982 |
| James Gillick Studio Ltd | Arts & recreation | 2011 |
| James Signature Care - Louth Ltd | Health & social care | 2026 |
| James Signature Care - Nottingham Ltd | Health & social care | 2025 |
| James Signature Care Limited | Health & social care | 2025 |
| James Smith Contractors (1957) Limited | Professional & scientific | 1957 |
| Jammy Cat Ltd | Extraterritorial | 2024 |
| Jananam Limited | Information & communication | 2020 |
| Javelin Irrigation Holdings Limited | Financial services | 2024 |
| Javelin Irrigation Systems Limited | Construction | 2006 |
| JB M&E Systems Ltd | Construction | 2015 |
| JB MES Group Ltd | Extraterritorial | 2021 |
| JB Renewable NRG Limited | Extraterritorial | 2021 |
| JBL Engineering Consultants Ltd | Other services | 2018 |
| Jdgs Holdings Limited | Professional & scientific | 2025 |
| JEH Holdings Limited | Professional & scientific | 2008 |
| JEM Atmospheric Effects Ltd | Wholesale & retail | 2025 |
| JEM Manufacturing Ltd | Manufacturing | 2025 |
| Jensen Consultancy Services Limited | Administrative & support | 2015 |
| Jewelbasic Limited | Wholesale & retail | 1990 |
| JHB Group Holdings Ltd | Financial services | 2025 |
| JHB Property Management Ltd | Real estate | 2025 |
| Jimmy Johnson Event & Production Services Ltd | Arts & recreation | 2022 |
| JJ Maidens Limited | Real estate | 2020 |
| JKD Trading Limited | Health & social care | 2018 |
| JKL ENG Limited | Professional & scientific | 2024 |
| JKP Contractors Ltd | Professional & scientific | 2025 |
| JL Piping Design Ltd | Professional & scientific | 2026 |
| JLP Cosmetics Ltd | Manufacturing | 2016 |
| JM Safety Ltd | Other services | 2017 |
| JM Smith Belchford Limited | Agriculture & fishing | 2022 |
| JMF Technology Ltd | Wholesale & retail | 2011 |
| JOE Buckner Associates Limited | Professional & scientific | 2002 |
| Joe's Plaice Limited | Hospitality | 2024 |
| John Cooper Farms Limited | Agriculture & fishing | 1981 |
| John E.Haith Limited | Manufacturing | 1961 |
| John Taylors (Lincolnshire) Limited | Real estate | 2002 |
| John Wilkinson Builders Limited | Construction | 2003 |
| Johnboyz Ltd | Construction | 2019 |
| Joint Dreams Ltd | Hospitality | 2018 |
| Jonathan Storr Financial Services Limited | Professional & scientific | 2008 |
| JP M&V Ltd | Health & social care | 2023 |
| JS Holdings (Louth) Ltd | Real estate | 2020 |
| JS Sweets Limited | Wholesale & retail | 2025 |
| JT Direct Dispatch Ltd | Transport & logistics | 2025 |
| Just 4-U Consult Ltd | Professional & scientific | 2025 |
| K D Marsh Limited | Health & social care | 2012 |
| K-TEK24 Limited | Professional & scientific | 2024 |
| Karaaslan Properties Ltd | Real estate | 2023 |
| KAY Property Law Limited | Professional & scientific | 2025 |
| KCG Property Solutions Ltd | Construction | 2024 |
| Kenmor Properties Limited | Households | 1986 |
| Kenwick News Ltd | Wholesale & retail | 2013 |
| Kenwick Park Golf Club Limited | Arts & recreation | 1991 |
| Kenwick Park Golf Shop Ltd | Administrative & support | 2003 |
| Kenwick Views Management Company Limited | Households | 2021 |
| Kesare Ltd | Real estate | 2024 |
| Kevigs Leisure Facilities Ltd | Administrative & support | 2024 |
| Key Accountancy & Payroll Services Limited | Professional & scientific | 2010 |
| King Edward VI Education Trust | Education | 2015 |
| Kingfisher Baits Limited | Agriculture & fishing | 2019 |
| Kingfisher Place Management Limited | Households | 1984 |
| Kingston Beck Limited | Real estate | 2021 |
| KJG Transport Ltd | Transport & logistics | 2019 |
| Knight Wilkinson Electrical Services Ltd | Construction | 2026 |
| Ks-Sleep Ltd | Manufacturing | 2024 |
| Kyoto Restaurant Limited | Hospitality | 2020 |
| L & C Farming Company Limited | Agriculture & fishing | 1986 |
| L R Engineering Contractors Ltd | Professional & scientific | 2026 |
| L&D Scaffold Access Ltd | Construction | 2025 |
| L.A.B Groundwork’S Ltd | Construction | 2025 |
| L.B. Property Limited | Real estate | 1987 |
| L.G.Dawson Limited | Agriculture & fishing | 1953 |
| LAC Accountancy & Bookkeeping Ltd | Professional & scientific | 2022 |
| Ladms Chambers C.I.C. | Health & social care | 2014 |
| Lakings Limited | Wholesale & retail | 2016 |
| Landover Property Limited | Extraterritorial | 2021 |
| Langley Park Property Ltd | Real estate | 2023 |
| Larders Bar Limited | Hospitality | 2024 |
| Laughtons of Louth Limited | Agriculture & fishing | 2007 |
| Laurance & Co Limited | Agriculture & fishing | 2014 |
| Lavender HR Ltd | Administrative & support | 2024 |
| LBC Louth Limited | | 2011 |
| Leaf Design Employee Ownership Trustees Limited | Professional & scientific | 2024 |
| Leaf Design UK Limited | Manufacturing | 2018 |
| Leah Jade Home Ltd | Wholesale & retail | 2024 |
| Leakes Masonry Limited | Manufacturing | 1973 |
| Leanpro Limited | Administrative & support | 2014 |
| Leen Valley Properties Limited | Households | 1964 |
| Lees 25 Limited | Hospitality | 2019 |
| Legcroft Ltd | Wholesale & retail | 2024 |
| Lemmington Ltd | Transport & logistics | 2012 |
| Leroy Seafood UK Limited | Manufacturing | 2022 |
| Let's Move With Sophie Limited | Real estate | 2023 |
| LEVEL9 Innovation IP Ltd | Professional & scientific | 2026 |
| Liam G Investments Limited | Real estate | 2013 |