| Rytech Ltd | Information & communication | 2017 |
| S & C Wong Innovations Limited | Transport & logistics | 2019 |
| S & J Electrical Northants Ltd | Construction | 2007 |
| S & K GUR Transport Limited | Transport & logistics | 2019 |
| S and K Aldous Construction Limited | Administrative & support | 2014 |
| S and L Construction Raunds Ltd | Administrative & support | 2020 |
| S and N Products (Northampton) Ltd | Wholesale & retail | 2016 |
| S C Elbrow Limited | Administrative & support | 2014 |
| S Curtis Holdings Ltd | Financial services | 2020 |
| S J Smith & SON Ltd | Wholesale & retail | 2025 |
| S J Technologie Limited | Wholesale & retail | 2003 |
| S Johnson Transport Limited | Administrative & support | 2016 |
| S L T Steel Services Ltd | Construction | 2020 |
| S Mobile Tyres Ltd | Wholesale & retail | 2025 |
| S P Properties 2021 Limited | Construction | 2021 |
| S Roberts Solutions Ltd | Transport & logistics | 2025 |
| S Walker Building Contractor Ltd. | Construction | 2016 |
| S&Lh Limited | Professional & scientific | 2019 |
| S&R Properties Development Ltd | Real estate | 2026 |
| S&T Property Maintenance Ltd | Transport & logistics | 2025 |
| S. J. Ingram & SON Ltd | Construction | 2019 |
| S. K. C. Fabrications Limited | Construction | 2006 |
| S.C. Builders (Thrapston) Limited | Construction | 2007 |
| S.J. Electronics Limited | Wholesale & retail | 1987 |
| S.K. Stainless Steel Polisher Ltd | Professional & scientific | 2017 |
| S.Skatulski Transport Ltd | Transport & logistics | 2020 |
| S.T. Flooring Limited | Wholesale & retail | 1999 |
| S.T. Holford Plumbing & Heating Ltd | Construction | 2002 |
| S.V.G. Ltd | Transport & logistics | 2016 |
| Sabar Installations Ltd | Construction | 2025 |
| Sabytrans Ltd | Transport & logistics | 2015 |
| Sadler Electrical Contractors Limited | Construction | 2013 |
| Safdrivers Ltd | Administrative & support | 2026 |
| Safe 2 Play Limited | Construction | 2022 |
| Safe Haven Lettings Ltd | Real estate | 2025 |
| Safe Kids Walking Ltd | Wholesale & retail | 2004 |
| Safe Packaging Ltd | Manufacturing | 2010 |
| Safe TC Ltd | Administrative & support | 2023 |
| Safepot Limited | Information & communication | 2025 |
| Safeway Private Hire Ltd | Transport & logistics | 2026 |
| Safewayridekettering Ltd | Transport & logistics | 2026 |
| Sage Communications & Events Limited | Professional & scientific | 2023 |
| Sagenix Solutions Limited | Information & communication | 2026 |
| Sahaj Properties Ltd | Real estate | 2025 |
| Sahaj Transport Limited | Transport & logistics | 2019 |
| Sahyog CIC | Health & social care | 2024 |
| Saint Finnen Limited | Information & communication | 2017 |
| Saints Screen Print Company Limited | Manufacturing | 2003 |
| Sairsam UK Ltd | Wholesale & retail | 2020 |
| Sakura Coffee Ltd | Hospitality | 2020 |
| Salaman Consulting Limited | Professional & scientific | 2021 |
| Salon Launch Ltd | Professional & scientific | 2023 |
| Saltason Ltd | Health & social care | 2026 |
| Salterford House Estates Limited | Real estate | 2022 |
| Salvare Associates Limited | Administrative & support | 2019 |
| SAM Leach Plastering Services Ltd | Construction | 2021 |
| SAM Nelson Consulting Ltd | Professional & scientific | 2018 |
| Samantha Thomas Limited | Real estate | 2022 |
| Sambol Services Limited | Construction | 2017 |
| Samuel Ross Group Limited | Administrative & support | 2018 |
| Sana K Ltd | Professional & scientific | 2023 |
| Sanctuary Blue Logistics Ltd | Transport & logistics | 2025 |
| Sangian Group Holdings Ltd. | Real estate | 2023 |
| Santen Care Services Ltd | Health & social care | 2026 |
| Santorsola Limited | Administrative & support | 2019 |
| Sapphire Developments (NE) Limited | Real estate | 2024 |
| Sapphire Dwellings (NE) Ltd | Real estate | 2024 |
| Sapphire Moon Ltd | Real estate | 2022 |
| Sarah Pendred Art Classes Limited | Education | 2017 |
| Sarah Underwood Hair Design Limited | Other services | 2024 |
| Sarchaw Food Store Ltd | Wholesale & retail | 2025 |
| Sareda Limited | Information & communication | 1994 |
| Sars Property Ltd | Real estate | 2023 |
| Sartivo Limited | Wholesale & retail | 2026 |
| SAS Food Limited | Wholesale & retail | 2013 |
| Sasha Core Beauty Ltd | Other services | 2016 |
| Sasso Asset Management Limited | Financial services | 2025 |
| Satellite Security Services Limited | Other services | 2005 |
| Satin Bower Ltd | Real estate | 2020 |
| Satra | Professional & scientific | 1919 |
| Satra Quality Assurance Limited | Professional & scientific | 1994 |
| Satra Services Limited | Extraterritorial | 2000 |
| Satra Technology Centre Limited | Professional & scientific | 1999 |
| Sawford Marine Limited | Manufacturing | 1998 |
| Saws Direct Limited | Wholesale & retail | 2009 |
| Saxon Management Services Limited | Professional & scientific | 2025 |
| Sayi Cars Ltd | Transport & logistics | 2025 |
| Sayvol Environmental and Building Services Limited | Administrative & support | 2002 |
| SBM Bratz Ltd | Transport & logistics | 2024 |
| SC & Co. Accountants Ltd | Professional & scientific | 2022 |
| Scale UP Outsourcing Ltd | Professional & scientific | 2023 |
| Scale UP S&P Ltd | Professional & scientific | 2026 |
| Scaled UP Kettering Ltd | Professional & scientific | 2025 |
| Scales Online Limited | Wholesale & retail | 2015 |
| Scales World UK Limited | Wholesale & retail | 2005 |
| Scalp Art Solutions Ltd | Other services | 2018 |
| Scanvault Limited | Information & communication | 2026 |
| Scatterplot Limited | Professional & scientific | 2023 |
| Schutz Integrated Property Systems Ltd | Construction | 2026 |
| Scomart Limited | Real estate | 2020 |