| Inline Brickwork (Lincoln) Ltd | Construction | 2012 |
| Inline Drainage Solutions Limited | Water & waste | 2015 |
| Innovative Garden Spaces Ltd | Construction | 2019 |
| Inspect (East Midlands) Ltd | Professional & scientific | 2017 |
| Int-Se Ltd | Education | 2021 |
| Intellisquare Ltd | Information & communication | 2023 |
| Interflora British Unit | Wholesale & retail | 1935 |
| International Purchasing Group Limited | Professional & scientific | 2003 |
| International Racing Limited | Professional & scientific | 2000 |
| International Shop Ltd | Wholesale & retail | 2026 |
| International Skills and Education Ltd | Professional & scientific | 2019 |
| Intervino Ltd | Wholesale & retail | 2005 |
| Intsight Global Limited | Information & communication | 2019 |
| ION Electrical Limited | Construction | 2012 |
| Irelands' Farms Limited | Agriculture & fishing | 1996 |
| IRH Consulting Limited | Administrative & support | 2011 |
| Irving Patrick Consulting Ltd | Construction | 2020 |
| Istambul Barber Ltd | Other services | 2023 |
| Istanbol BRB Ltd | Other services | 2026 |
| Istanbul Sleaford Ltd | Other services | 2026 |
| IV Creative Limited | Manufacturing | 2012 |
| IV Creative Solutions Ltd | Professional & scientific | 2022 |
| Ivory Care Limited | Real estate | 1999 |
| J and L Stone Ornaments Ltd | Manufacturing | 2021 |
| J E Services Limited | Administrative & support | 2003 |
| J E Severs Funeral Service Limited | Other services | 2012 |
| J Goddard DRY Lining Ltd | Construction | 2016 |
| J H & S Limited | Construction | 2015 |
| J J Parr Limited | Construction | 2006 |
| J Jenkins Electrical Ltd | Wholesale & retail | 2009 |
| J Welch Hygienist Ltd | Health & social care | 2006 |
| J West Services Ltd | Construction | 2025 |
| J Wilson Bathrooms Limited | Wholesale & retail | 2021 |
| J Wright Projects Ltd | Construction | 2023 |
| J&N Trading (Lincolnshire) Ltd | Wholesale & retail | 2006 |
| J. HIX (Sleaford) Limited | Construction | 1961 |
| J. Tokley Contracting Limited | Construction | 2026 |
| J.Bdigitalproducts Ltd | Wholesale & retail | 2025 |
| J.D. Engineering Services Limited | Real estate | 1980 |
| J.E.M.I. Construction Ltd | Construction | 2010 |
| J.L. Priestley & Co. Limited | Manufacturing | 1974 |
| J.P Autos of Sleaford Ltd | Wholesale & retail | 2018 |
| J.T. Lord & SON (Sleaford) Limited | Wholesale & retail | 1978 |
| J2B Travel Ltd | Transport & logistics | 2021 |
| Jaguar Nova Holdings Ltd | Financial services | 2019 |
| Jakmadhar Projects Ltd | Arts & recreation | 2017 |
| James David HCM Limited | Professional & scientific | 2025 |
| Jamieleecosmetics Ltd | Wholesale & retail | 2022 |
| Jamsons Estate Agents Ltd | Real estate | 2025 |
| Jamsons Holdings Ltd | Real estate | 2016 |
| Jane Downey Consultancy Ltd | Professional & scientific | 2015 |
| Jashan 1921 Ltd | Hospitality | 2025 |
| Jasmine Healthcare Limited | Health & social care | 2003 |
| Jason Wilsher-Mills Ltd | Education | 2014 |
| Jasper Klein Associates Ltd | Information & communication | 2014 |
| JC Development & Restoration Ltd | Real estate | 2026 |
| JC Groundwork & Drainage Limited | Water & waste | 2018 |
| JC Social Care Limited | Health & social care | 2008 |
| JCO Developments Limited | Construction | 2016 |
| Jconet Ltd | Information & communication | 2021 |
| JD Prosper Properties Ltd | Real estate | 2020 |
| JDJ Financials Limited | Professional & scientific | 2025 |
| Jfsa Ltd | Real estate | 2018 |
| Jim's Gym and Studio Ltd | Arts & recreation | 2022 |
| Jim's Therapy Rooms Ltd | Health & social care | 2026 |
| JKR Sweepers Ltd | Administrative & support | 2024 |
| JL Priestley Bulk Services Limited | Transport & logistics | 2022 |
| JLP Food Group Ltd | Manufacturing | 2024 |
| JLR Civils Ltd | Construction | 2026 |
| JOE Carr Removals & Storage Ltd | Transport & logistics | 2021 |
| John Earley Consulting Limited | Professional & scientific | 2013 |
| John F Wooster Construction (Lincs) Limited | Construction | 2004 |
| John Peat Motors Limited | Wholesale & retail | 2001 |
| John Pittock Ltd | Professional & scientific | 2021 |
| John Pocklington & SON Limited | Transport & logistics | 2017 |
| Jones Campbell Roofing & Cladding Ltd | Construction | 2023 |
| Joyful Timber Limited | Professional & scientific | 2024 |
| JSM Accounting and Bookkeeping Services Ltd | Professional & scientific | 2009 |
| Juleff Associates Ltd | Real estate | 2014 |
| Jumbo Software Ltd | Information & communication | 2026 |
| Juniper ARC Design Ltd | Professional & scientific | 2026 |
| JV Commercial Painting Solutions Ltd | Construction | 2024 |
| JW Conservation Limited | Professional & scientific | 2013 |
| K D Camden-Smith Ltd | Health & social care | 2010 |
| K Harold Associates Limited | Professional & scientific | 2012 |
| K.N.H.C. Limited | Health & social care | 2007 |
| K.Russell Technical Publications Limited | Professional & scientific | 2012 |
| K2 Healthcare Limited | Health & social care | 2016 |
| K2B Holdings Limited | Financial services | 2020 |
| K2B Limited | Wholesale & retail | 2003 |
| Kaleidoscope Property Consulting Ltd | Real estate | 2015 |
| Kaleidoscope Property Services Limited | Real estate | 2015 |
| Kalika Devi Limited | Hospitality | 2025 |
| KAN Catering Ltd | Hospitality | 2019 |
| Kannipha Thai UK Limited | Hospitality | 2013 |
| Kapiti Holdings Limited | Financial services | 2017 |
| Kapiti Property Limited | Other services | 2017 |
| Kass Properties Limited | Real estate | 2009 |
| Kazo Security Ltd | Administrative & support | 2024 |
| KAZO-K9 Ltd | Transport & logistics | 2014 |