| Money Minder Financial Services (Woodhall Spa) Limited | Financial services | 2016 |
| Money Minder Financial Services Limited | Financial services | 2000 |
| Moor Farm Building Co. Limited | Construction | 2004 |
| Moore Improvements Ltd | Construction | 2023 |
| Morgan (Norfolk) Building Limited | Construction | 2016 |
| Motor and Diesel Engineering (Anglia) Limited | Wholesale & retail | 1987 |
| Motor Emotion Ltd | Wholesale & retail | 2017 |
| Mouche Properties Limited | Real estate | 2013 |
| Move My Pet Ltd | Extraterritorial | 2023 |
| MR Paving & Sons Ltd | Construction | 2020 |
| MRS Inked UK Limited | Professional & scientific | 2023 |
| Msac Solutions Limited | Professional & scientific | 2021 |
| MSJ Engineering Ltd | Professional & scientific | 2025 |
| MSK Doctors & Associates Limited | Wholesale & retail | 2019 |
| MSM Millview Ltd | Wholesale & retail | 2023 |
| MT Environmental Limited | Water & waste | 2023 |
| Munitor Engineering Services Limited | Professional & scientific | 2015 |
| Murus Fire Protection Limited | Public administration | 2021 |
| Music Street | Arts & recreation | 2012 |
| Music Workshop Coffeehouse C.I.C. | Hospitality | 2021 |
| Must BE Done Ltd | Real estate | 2025 |
| Mychild's Nursery Limited | Education | 2015 |
| Médica Recordings Ltd | Manufacturing | 2022 |
| N & D Badley Limited | Construction | 2011 |
| N18 Group Ltd | Administrative & support | 2026 |
| N18 Media Ltd | Real estate | 2022 |
| National Matrix Limited | Administrative & support | 2002 |
| Natural Bird Food Company Ltd | Wholesale & retail | 2013 |
| Natural Dog & Cat Food Ltd | Manufacturing | 2020 |
| NB (Seed Processors) Limited | Agriculture & fishing | 1979 |
| Ndfc Distribution Ltd | Wholesale & retail | 2010 |
| NE Designs Ltd | Professional & scientific | 2024 |
| Nelcreate Limited | Information & communication | 2014 |
| New Image Gym Ltd | Other services | 2019 |
| New Image Gym Ruskington Ltd | Other services | 2025 |
| New Inn (Folkingham) Ltd | Hospitality | 2025 |
| New Life Church Ministries (Sleaford) | Other services | 2013 |
| New Life Conference Centre Limited | Other services | 2006 |
| New Life Home Developments Limited | Construction | 2018 |
| Newman Moore Limited | Construction | 2019 |
| Nexera Consultancy Ltd | Information & communication | 2026 |
| Nifty IT Services Ltd | Information & communication | 2023 |
| Nigel Brands UK Ltd | Administrative & support | 2023 |
| Nightingale Nursing & Care Home Limited | Health & social care | 2026 |
| Nikola (Sleaford) Limited | Hospitality | 2024 |
| Nisantasi Limited | Hospitality | 2016 |
| Niva Inc Ltd | Wholesale & retail | 2018 |
| NJA Property Management Limited | Real estate | 2002 |
| Njapm Homes Limited | Construction | 2020 |
| Nncc Limited | Education | 2022 |
| NNT Ltd | Wholesale & retail | 2014 |
| NO.2 Blossom Street Ltd | Wholesale & retail | 2025 |
| Noisy RAM Limited | Information & communication | 2013 |
| Nora Jaxx Limited | Other services | 2026 |
| North Group (Lincs) Limited | Construction | 2019 |
| North Group Properties Limited | Real estate | 2021 |
| North Street Digby Management Limited | Households | 2015 |
| Northfields Therapy Services Limited | Health & social care | 2023 |
| Northgate Development Lincs Limited | Construction | 1990 |
| Northwood Camshire Limited | Real estate | 2006 |
| NOT ALL BAD Training | Education | 2011 |
| Nova Science Ltd | Wholesale & retail | 2026 |
| Novuss Federation of United Kingdom CIC | Arts & recreation | 2022 |
| NSC Manufacturing Limited | Manufacturing | 1993 |
| NUMBER925 Limited | Wholesale & retail | 2024 |
| NW Building & Civil Engineering Services Ltd | Construction | 2013 |
| O. W. Ward Ltd | Other services | 2017 |
| Oakleyfit Ltd | Arts & recreation | 2024 |
| Oakview Kitchens & Bedrooms Ltd | Construction | 2026 |
| Oakwick Holdings Limited | Financial services | 2026 |
| Oakwick Utility Arborists Ltd | Agriculture & fishing | 2005 |
| Obsidian Design & Creation Limited | Manufacturing | 2018 |
| Offgrid Property Ltd | Construction | 2024 |
| Offgrid Works Ltd | Construction | 2021 |
| Old Ship Inn Pointon Ltd | Hospitality | 2025 |
| Old World - New World Recordings Ltd | Manufacturing | 2023 |
| Olivers Motorcycles Limited | Wholesale & retail | 2015 |
| Oneworldgoods Ltd | Wholesale & retail | 2025 |
| Onswitch Limited | Professional & scientific | 2006 |
| Optimise Engineering Limited | Professional & scientific | 2024 |
| Opus LED Limited | Manufacturing | 2012 |
| Orchard CFO Services Ltd | Professional & scientific | 2025 |
| Orchard Court Residential Home Limited | Health & social care | 1998 |
| Orchard Store and Services (1950) Ltd | Agriculture & fishing | 2018 |
| Orlando Tong Entertainment Limited | Arts & recreation | 2021 |
| OS Medical Ltd | Health & social care | 2024 |
| Ownerracehorse Ltd | Arts & recreation | 2025 |
| Oxendon House Care Home Limited | Health & social care | 2002 |
| Oxenford Farm Management Company Limited | Professional & scientific | 2008 |
| P & M Design Partners Ltd | Professional & scientific | 2018 |
| P & P Tree Services (Lincs) Ltd | Administrative & support | 2025 |
| P a Bristow Limited | Other services | 2000 |
| P F Coldstores Ltd | Construction | 2025 |
| P L Installations Ltd | Manufacturing | 2009 |
| P.A. Booth & Co., Ltd | Agriculture & fishing | 1970 |
| P.F.Miller Limited | Extraterritorial | 1960 |
| P.S Drives Patios and Ground Works Ltd | Construction | 2019 |
| P4U Wellbeing Ltd | Wholesale & retail | 2026 |
| Padel Masters Ltd | Manufacturing | 2024 |
| PAK Elite Ltd | Construction | 2020 |