| Naeem Medics Limited | Health & social care | 2018 |
| Nassim Engineering Limited | Professional & scientific | 1991 |
| National Auto Breakers Ltd | Wholesale & retail | 2026 |
| Natural Smiles Dental Group Ltd | Health & social care | 2023 |
| Naturally Best Marketing Limited | Professional & scientific | 2012 |
| Nature's Essence Ltd | Manufacturing | 2025 |
| Naturestrong Limited | Wholesale & retail | 2018 |
| Nautx Aviation Ltd | Transport & logistics | 2018 |
| Nautx Limited | Professional & scientific | 2016 |
| Nayma Limited | Health & social care | 2025 |
| NE Plus Ultra Limited | Information & communication | 2008 |
| Necmed Consulting Ltd | Health & social care | 2017 |
| Need Bright Resources Ltd | Education | 2021 |
| NEH Animal Feed and Supplies Limited | Wholesale & retail | 2025 |
| Nerina Farmer Limited | Professional & scientific | 2007 |
| Neringa&Andrius Ltd | Transport & logistics | 2022 |
| Nest Empire Properties Limited | Real estate | 2024 |
| New Beijing Catering Ltd | Hospitality | 2025 |
| New Haven Pathways Ltd | Hospitality | 2025 |
| New Leaf Dog Rescue C.I.C. | Agriculture & fishing | 2024 |
| New Ocean 2019 Ltd | Hospitality | 2019 |
| New Ocean Trading Limited | Hospitality | 2025 |
| New View Glass and Glazing Ltd | Construction | 2025 |
| New View Windows Ltd | Construction | 2017 |
| Newage Global Traders Ltd | Wholesale & retail | 2022 |
| Newman Trades and Labour Ltd | Administrative & support | 2025 |
| Newton & Sims Coal Merchants Ltd | Wholesale & retail | 2021 |
| Newton Fallowell (Boston) Limited | Real estate | 2013 |
| Newton Fallowell (Horncastle) Limited | Real estate | 2020 |
| Newton Fallowell (Skegness) Limited | Real estate | 1999 |
| Newton's Corner Limited | Financial services | 2022 |
| Nexustech Services Limited | Information & communication | 2025 |
| Nfgu Coaching Ltd | Arts & recreation | 2025 |
| NG25 Limited | Financial services | 2017 |
| Ngoldenbee Limited | Wholesale & retail | 2023 |
| NGP Transport Limited | Transport & logistics | 2020 |
| Nicad Consultancy Services Limited | Professional & scientific | 2015 |
| Nicholls Timber Limited | Wholesale & retail | 2017 |
| Nick Johnson Ltd | Professional & scientific | 2018 |
| Nicks Taxis of Boston Ltd | Transport & logistics | 2023 |
| Nicola Burrell Mortgage Solutions Ltd | Financial services | 2016 |
| Nigel FOX Fine Cars Ltd | Wholesale & retail | 2025 |
| Night & Day Diesel Injection Services Limited | Wholesale & retail | 2011 |
| NIK N MIX Ltd | Hospitality | 2022 |
| Nikaline Limited | Transport & logistics | 2018 |
| Nike Ajewole Healthcare Limited | Health & social care | 2021 |
| Nikki's Nesties Ltd | Manufacturing | 2021 |
| NJA Haulage Ltd | Transport & logistics | 2025 |
| NKO Lettings Ltd | Real estate | 2026 |
| NO 1 Auto Wash Boston Ltd | Wholesale & retail | 2026 |
| Noble Assetcompany Ltd | Real estate | 2023 |
| Nolan Safety Limited | Public administration | 2019 |
| Norfolk Lane Ltd | Health & social care | 2025 |
| Norfolk Lane Properties Ltd | Real estate | 2025 |
| Northern Soul Tattoo Ltd | Other services | 2022 |
| NOT a Racer Limited | Wholesale & retail | 2026 |
| Nova Industrial Services Ltd | Manufacturing | 2023 |
| NT & LT Properties Limited | Real estate | 2018 |
| Nubium Ltd | Information & communication | 2026 |
| Numeri Group Ltd | Information & communication | 2018 |
| NY Locums Ltd | Health & social care | 2022 |
| O & S Holdings Ltd | Real estate | 2025 |
| O K Private Enterprises Limited | Information & communication | 2006 |
| O&M Market Ltd | Wholesale & retail | 2016 |
| O.D. Transport Limited | Transport & logistics | 2023 |
| Oak House Financial Ltd | Financial services | 2021 |
| Oak Lodge Accountancy Ltd | Professional & scientific | 2014 |
| Oakbridge Vehicles Ltd | Professional & scientific | 2025 |
| Oakdale (Weybridge) Ltd | Real estate | 2016 |
| Oakdale Products Limited | Wholesale & retail | 2008 |
| Oakie Dokie Signs Ltd | Professional & scientific | 2025 |
| Oaklands Brickwork Ltd | Construction | 2018 |
| Oakwood House Independent School Ltd | Education | 2023 |
| Oasis for Hair Limited | Other services | 2003 |
| Oats and Furtado Investments Ltd | Real estate | 2022 |
| Ocean Harvest Trading Ltd | Hospitality | 2023 |
| Oddjobscott Limited | Administrative & support | 2023 |
| Offset Estate Ltd | Financial services | 2025 |
| Offset Properties Limited | Real estate | 2024 |
| OJ OIL Services Ltd | Construction | 2025 |
| Oj's Salon Limited | Other services | 2014 |
| OK Catering Chequers Limited | Hospitality | 2018 |
| Old Leake Leisure Park Limited | Hospitality | 2026 |
| Old Mill Court Managers Limited | Households | 2007 |
| Old Smoke Ltd | Wholesale & retail | 2017 |
| Oldman's Store Ltd | Manufacturing | 2023 |
| Oldrid & Co. Pension Trustee Limited | Other services | 2015 |
| Oliana Properties Ltd | Real estate | 2023 |
| Oliana Property Investments Ltd | Real estate | 2023 |
| Olive & Weston Limited | Other services | 2017 |
| Olive & Weston Merchandise Limited | Wholesale & retail | 2019 |
| Omnitail Ltd | Wholesale & retail | 2020 |
| Omtas Ltd | Hospitality | 2025 |
| ON the Go Transport Ltd | Transport & logistics | 2018 |
| ON24 (UK) Limited | Professional & scientific | 2004 |
| One Move Marketing Ltd | Professional & scientific | 2025 |
| One Stop Europe Ltd | Wholesale & retail | 2015 |
| One Stop Spoilers Limited | Wholesale & retail | 2021 |
| Onward Wellbeing Services Ltd | Health & social care | 2024 |
| Opteammaster AI Ltd | Information & communication | 2025 |