| North Moss Supplies Limited | Manufacturing | 2017 |
| North Precision Engineering Limited | Manufacturing | 2024 |
| North Westy Ltd | Wholesale & retail | 2011 |
| North Wolds Construction Ltd | Construction | 2024 |
| Northbay Seafoods Limited | Wholesale & retail | 2026 |
| Northchart Limited | Information & communication | 2016 |
| Northern Fish Imports Limited | Manufacturing | 2014 |
| Northern Sauce Ltd | Information & communication | 2022 |
| Northern Sole (Grimsby) Limited | Wholesale & retail | 2004 |
| Northstar (Grimsby) Properties Limited | Real estate | 1998 |
| Northwall Investments and Developments Limited | Real estate | 2018 |
| Norton CM Ltd | Construction | 2014 |
| Nosniklam Services Ltd | Administrative & support | 2013 |
| NOT Just Sourcing Limited | Real estate | 2025 |
| NOT Just Walls Limited | Real estate | 2019 |
| Noton Estates Limited | Construction | 2025 |
| Noton Lettings Ltd | Real estate | 2022 |
| Nottingham House 4 Ltd | Hospitality | 2020 |
| Nova Research Ltd | Agriculture & fishing | 2023 |
| Novamix Ltd | Wholesale & retail | 2019 |
| NOW Entertain ME Ltd | Other services | 2018 |
| NP Collective Holdings Limited | Financial services | 2021 |
| NPT Joinery and Building Ltd | Construction | 2024 |
| NR4C Ltd | Hospitality | 2020 |
| NRL Construction Ltd | Construction | 2025 |
| NRP Industries Ltd | Professional & scientific | 2024 |
| NRT Electrical Design Limited | Administrative & support | 1999 |
| NS Medical Services Ltd | Health & social care | 2025 |
| Nsama and Sons Limited | Health & social care | 2015 |
| NSB Property Developments Ltd | Construction | 2020 |
| Nsso Ltd | Education | 2023 |
| NT & EO Ltd | Real estate | 2023 |
| Nt-Highways Consultants Limited | Construction | 2021 |
| Ntex Limited | Transport & logistics | 2003 |
| Nuclear Technical Authors Limited | Other services | 2010 |
| Nucleus Web Design Limited | Information & communication | 2015 |
| Nunns of Grimsby Limited | Wholesale & retail | 1980 |
| Nunny's Farm CIC | Agriculture & fishing | 2017 |
| Nunny's Little Farmers Ltd | Education | 2022 |
| Nurtrio Limited | Financial services | 2007 |
| NV Properties Investment Ltd | Hospitality | 2023 |
| NV Training Ltd | Education | 2025 |
| NW Inspection Solutions Ltd | Professional & scientific | 2024 |
| Nwphs Limited | Construction | 2014 |
| NXT Level Windows Limited | Construction | 2021 |
| O'Boyle Civil Engineering Limited | Construction | 1991 |
| O'Connor Financial Solutions Limited | Professional & scientific | 2014 |
| O. Turner Limited | Construction | 1983 |
| O.K Electrical Install Ltd | Construction | 2024 |
| OAC Studio Limited | Other services | 2021 |
| OAC Training Limited | Education | 2025 |
| Oakfield Lane (Waltham) Management Company Limited | Real estate | 2018 |
| Oakford Management Limited | Real estate | 1992 |
| Oakhill Homes Limited | Construction | 2015 |
| Oakland's Resources Limited | Wholesale & retail | 2018 |
| Oaklands Hall Hotel Limited | Hospitality | 2010 |
| Oaktree Residential Holdings Limited | Real estate | 2026 |
| Oakwood Driveways & Paving Ltd | Construction | 2024 |
| Oakwood Maintenance Limited | Construction | 2017 |
| Oana Donici Limited | Health & social care | 2023 |
| Oasis Food Bar Ltd | Hospitality | 2026 |
| OBA Filleting Services Limited | Manufacturing | 2026 |
| Obsidian Estates Limited | Real estate | 2015 |
| Obsidian Mind Limited | Health & social care | 2024 |
| Ocean Bounty Limited | Wholesale & retail | 1990 |
| Ocean Filleting Services Ltd | Manufacturing | 2025 |
| Ocean Fish Bar (Cleethorpes) Ltd | Hospitality | 2019 |
| Ocean Floors Ltd | Construction | 2018 |
| Ocean Harvest Limited | Administrative & support | 2003 |
| Ocean Seafoods Limited | Wholesale & retail | 2023 |
| Ocean Treats Ltd | Wholesale & retail | 2025 |
| Ocean's Bay Aquatics Ltd | Wholesale & retail | 2015 |
| Oceanblue Logistics Limited | Transport & logistics | 2005 |
| Oceans Finest Limited | Wholesale & retail | 2007 |
| Octa Project Management Ltd | Construction | 2024 |
| OD Medical Ltd | Health & social care | 2025 |
| Oddball Promotions Limited | Hospitality | 2001 |
| Odorchem Ltd | Wholesale & retail | 2026 |
| Odour Doctor Limited | Construction | 2017 |
| Office Friends Holdings Ltd | Financial services | 2024 |
| Office Friends Ltd | Wholesale & retail | 2007 |
| Office Friends Systems Ltd | Wholesale & retail | 2014 |
| Offshore E&I Services Ltd | Construction | 2018 |
| Offshore Training Centre (Grimsby) Limited | Education | 2023 |
| Og's Catering Services Limited | Manufacturing | 2025 |
| Oilexe Limited | Mining & quarrying | 2010 |
| OJ Investments (Doncaster) Ltd | Financial services | 2018 |
| Ojay Enterprises Limited | Other services | 2019 |
| OJL Services GY Ltd | Administrative & support | 2024 |
| Okeyanju Medicare Limited | Health & social care | 2025 |
| OKO Golf Ltd | Wholesale & retail | 2025 |
| Olbek Fishing Company Limited | Agriculture & fishing | 1967 |
| Old Clee Bakery Ltd | Manufacturing | 2014 |
| Old Clee Primary Academy | Education | 2013 |
| Old Orchard Properties Ltd | Real estate | 2025 |
| Old Paddock Court Management Company Limited | Households | 2004 |
| Old Vicarage Developments Limited | Households | 2003 |
| Oldclee Inspection Services Ltd | Professional & scientific | 2024 |
| Olden Thymes Grounds Care Ltd | Administrative & support | 2019 |
| OLG Trans Limited | Transport & logistics | 2022 |