| Sandecja Ltd | Transport & logistics | 2025 |
| Sanders Uniform Limited | Wholesale & retail | 2020 |
| Sandu Borta Haulage Limited | Transport & logistics | 2024 |
| Sandy Lane Publishing Ltd | Information & communication | 2019 |
| Santa POD Racers Club Limited | Professional & scientific | 2003 |
| Sapphire Oaks Asset Management Limited | Real estate | 2024 |
| Sapphire Property Portfolio Ltd | Real estate | 2026 |
| Sapphire Support Consultancy Limited | Administrative & support | 2022 |
| Sarah's Rushden Ltd | Other services | 2017 |
| Saratex Ltd | Health & social care | 2013 |
| Sarpongs Limited | Information & communication | 2016 |
| SAS Rushden Limited | Administrative & support | 2025 |
| SAVU21 Trans Ltd | Transport & logistics | 2021 |
| SBP Solutions Ltd | Real estate | 2022 |
| SC Investment Properties Limited | Real estate | 2024 |
| SCA Motorsport Services Ltd | Administrative & support | 2017 |
| Scarrott Unlimited FUN Parks Ltd | Arts & recreation | 2026 |
| Scarrott's Event Services Ltd | Hospitality | 2023 |
| Scolaric Ltd | Wholesale & retail | 2025 |
| Scorpion Services International LLP | | 2007 |
| Screen Neurodiversity Ltd | Information & communication | 2025 |
| Sdfali Ltd | Wholesale & retail | 2025 |
| SDW Commercial Vehicle Consultants Ltd | Wholesale & retail | 2026 |
| Sean Kaye Limited | Administrative & support | 2014 |
| SEC Accounting Services Ltd | Professional & scientific | 2021 |
| Seeded Property Ltd | Real estate | 2024 |
| Select Stone Recycling Limited | Construction | 2021 |
| Serve | Health & social care | 1994 |
| Seska Ltd | Professional & scientific | 2024 |
| Seve Holdings Ltd | Financial services | 2022 |
| Seventy Three Executive Private Hire Limited | Transport & logistics | 2026 |
| SF Interiors Ltd | Construction | 2017 |
| Sfjr Properties Ltd | Real estate | 2022 |
| Sh-Education Ltd | Education | 2023 |
| Shanghai Foods Takeaway Limited | Hospitality | 2022 |
| Sharon Scott Associates Ltd | Education | 2025 |
| Shaun Cooper Plumbing Limited | Construction | 2003 |
| SHC Property Management Ltd | Households | 2020 |
| Shires Passenger Transport Limited | Transport & logistics | 2006 |
| Shivani Fitness Ltd | Arts & recreation | 2023 |
| Shofna Coworking Limited | Administrative & support | 2025 |
| Shore Tanning Ltd | Other services | 2025 |
| Shortlancer Limited | Information & communication | 2017 |
| Showermaster Limited | Extraterritorial | 1980 |
| Showhome Warehouse Limited | Real estate | 2003 |
| Shrimpton Ltd | Real estate | 2019 |
| Shrink Polymer Systems Ltd | Manufacturing | 2024 |
| Shulman Property Ltd | Real estate | 2015 |
| Sibri Trucking Limited | Transport & logistics | 2019 |
| Sibutseng Ltd | Health & social care | 2022 |
| Sidey Design Associates Limited | Professional & scientific | 2007 |
| Signal & Sense Ltd | Professional & scientific | 2026 |
| Sikora Ltd | Transport & logistics | 2021 |
| Silly Simple Limited | Professional & scientific | 2024 |
| Silver Knitting Machines Ltd. | Wholesale & retail | 1990 |
| Silver Sewing Machines Ltd. | Wholesale & retail | 2009 |
| Simalisys Limited | Real estate | 2008 |
| Simmonn Ltd | Transport & logistics | 2015 |
| Simon Acres Group Ltd | Professional & scientific | 2018 |
| Simon Acres Recruitment Ltd | Administrative & support | 2020 |
| Simon Huckle Holdings Limited | Administrative & support | 2023 |
| Simon White Business Development Ltd. | Administrative & support | 2014 |
| Simserve Limited | Manufacturing | 2013 |
| Sinbel Ltd | Information & communication | 2020 |
| Sinna Films Limited | Arts & recreation | 1981 |
| SJC Refinishers Ltd | Wholesale & retail | 2014 |
| Sjdh Ltd | Financial services | 2022 |
| SJE Direct Ltd | Transport & logistics | 2026 |
| Sjrd Limited | Financial services | 2013 |
| Skae Properties Limited | Real estate | 2024 |
| Skyetan Limited | Other services | 2022 |
| Skyline Asset Management Ltd | Households | 2023 |
| SL & AH Affittare Limited | Real estate | 2001 |
| Smart RPE Solutions Limited | Health & social care | 2024 |
| Smith and Stankevitch Consulting Limited | Professional & scientific | 2025 |
| Smithfilmstudios Ltd | Professional & scientific | 2018 |
| Snowdon Homes (Melton Mowbray) Limited | Construction | 2022 |
| SO Clean Window Cleaning Services Ltd | Other services | 2023 |
| Soda Blast East Ltd. | Administrative & support | 2019 |
| Soela Aesthetics Ltd | Other services | 2022 |
| Sofia Moliterno Sports Therapy Ltd | Other services | 2022 |
| Softlearn Limited | Arts & recreation | 1998 |
| Sohi Haulage Ltd | Transport & logistics | 2018 |
| Sondr App Limited | Information & communication | 2025 |
| Sophies Sips Ltd | Manufacturing | 2026 |
| Soteria UK Security & Automation Ltd | Information & communication | 2011 |
| Souza Holdings Limited | Real estate | 2025 |
| SOY WAX Village Ltd | Manufacturing | 2022 |
| Sparta Construction 1980 Ltd | Construction | 2020 |
| Spectre Assets Ltd | Real estate | 2020 |
| Spice Bar Rushden Ltd | Hospitality | 2022 |
| Spice Lounge Northants Ltd | Hospitality | 2025 |
| Spintex Limited | Health & social care | 2023 |
| Springfield Property Investments (Rushden) Ltd | Real estate | 2024 |
| Spud Central Limited | Hospitality | 2022 |
| Spud Place Limited | Hospitality | 2025 |
| SRP Construction Ltd | Construction | 2022 |
| SS Salon Group Ltd | Other services | 2023 |
| Sspsi Ltd | Professional & scientific | 2022 |
| ST Gyles Ltd | Administrative & support | 2003 |