| Sassy Spirit Limited | Wholesale & retail | 2015 |
| SAY Cheese (Louth) Limited | Wholesale & retail | 2007 |
| Scallen Developments Ltd | Real estate | 2024 |
| Scamans Eggs Limited | Wholesale & retail | 2019 |
| Scott Mckay Hair Limited | Other services | 2018 |
| SDH Engineering Projects Limited | Professional & scientific | 2024 |
| Sean Lawson Land Limited | Wholesale & retail | 2001 |
| Seatrade U.K. Ltd | Wholesale & retail | 2022 |
| Seaview Property Solutions UK Ltd | Real estate | 2021 |
| Select Management Solutions Ltd | Professional & scientific | 2025 |
| Seven Takeaway Ltd | Hospitality | 2025 |
| SG Electrical (Lincs) Limited | Construction | 2019 |
| SG Engineering Consultants Limited | Professional & scientific | 2008 |
| Shafah Service Limited | Information & communication | 2024 |
| Shark Homes Ltd | Real estate | 2019 |
| Sharpley Consulting Limited | Professional & scientific | 2016 |
| Shaun Clark Landscapes Limited | Administrative & support | 2003 |
| Sheppard Technologies Ltd | Information & communication | 2021 |
| Sherwood Vale Developments Limited | Construction | 1962 |
| Shire Baked Potatoes Limited | Manufacturing | 2003 |
| Shire Event Styling Ltd | Other services | 2026 |
| Shire Locks Ltd | Other services | 2022 |
| Shirleys Limited | Other services | 2011 |
| Siautek Ltd | Manufacturing | 2022 |
| Signboard Systems Ltd. | Manufacturing | 2009 |
| Silvester & Sons Ltd | Construction | 2021 |
| Simon Anderson Property Ltd | Real estate | 2020 |
| Sineshift Limited | Information & communication | 2013 |
| Sixteen George Street (Louth) Management Company Limited | Real estate | 2002 |
| SK Structural Carpentry Limited | Construction | 2024 |
| Skendleby Events LLP | | 2023 |
| Skills Holdings Ltd | Education | 2017 |
| SL & AC Autos Ltd | Wholesale & retail | 2024 |
| Smash Kulture Limited | Hospitality | 2025 |
| Smith Security UK Limited | Administrative & support | 2013 |
| SMK Social Work Services Limited | Health & social care | 2025 |
| Snape Developments Limited | Construction | 2022 |
| Snape Properties Holdings Limited | Construction | 2022 |
| Snape Properties Limited | Construction | 1984 |
| Snape Residential Ltd | Real estate | 2025 |
| SNJ Capital Limited | Financial services | 2022 |
| Sofina EAR Care Ltd | Health & social care | 2020 |
| Softwair UK Limited | Information & communication | 2022 |
| Somercotes Retail Ltd | Wholesale & retail | 2025 |
| Somercotes Storage Ltd | Transport & logistics | 2025 |
| Soteria Engineering Inspection Services Ltd | Professional & scientific | 2017 |
| South Ormsby Community Interest Company | Hospitality | 2017 |
| South Ormsby Estate Limited | Extraterritorial | 2025 |
| South Ormsby Events Limited | Arts & recreation | 2017 |
| South Ormsby HR Limited | Administrative & support | 2017 |
| South Ormsby Park Limited | Agriculture & fishing | 2017 |
| South Ormsby Trading Limited | Wholesale & retail | 2021 |
| SPC UK Services Ltd | Agriculture & fishing | 2021 |
| Speccetera Ltd | Professional & scientific | 2025 |
| Specialspeed Limited | Construction | 1997 |
| Speed 9521 Limited | Wholesale & retail | 2003 |
| Spicescape | Administrative & support | 2015 |
| Spire Window Systems (Lincolnshire) Ltd | Professional & scientific | 1989 |
| Spiretec Ltd | Wholesale & retail | 2010 |
| SPL Pipework and Fabrications Limited | Real estate | 2014 |
| Splatterworks Limited | Wholesale & retail | 2023 |
| Spout Yard Park Management Trust Limited | Arts & recreation | 2001 |
| Spring Court Residents Association (Louth) Limited | Households | 1991 |
| Spring Home Improvements Limited | Construction | 2024 |
| Springfield Park Retirement Limited | Real estate | 2014 |
| Spudwagon Ltd | Hospitality | 2023 |
| Square Deal Carpets Horncastle Limited | Wholesale & retail | 1974 |
| SRL Windows & Conservatories Limited | Construction | 2009 |
| Staccato Property Management Limited | Real estate | 2017 |
| Stalwart Engineering Services Ltd | Professional & scientific | 2025 |
| Stax of WAX Ltd | Manufacturing | 2018 |
| Steadfast Property People Ltd | Households | 2024 |
| Stech (UK) Ltd | Administrative & support | 2005 |
| Stemgold Peas Limited | Agriculture & fishing | 2002 |
| Steve Graves Steelwork & Cladding Ltd | Construction | 2003 |
| Stevens Property Holdings Ltd | Financial services | 2020 |
| Stevens Property Management Limited | Real estate | 2004 |
| Stevens Property Services Ltd | Real estate | 2022 |
| Stewton Yews Ltd | Financial services | 2024 |
| STK Property Limited | Construction | 2021 |
| Stokt Limited | Information & communication | 2020 |
| Stone ETC Limited | Transport & logistics | 2004 |
| STR Partnership Limited | Financial services | 2013 |
| Straight Arrow Solutions Limited | Professional & scientific | 2017 |
| Straw Pellets Ltd | Manufacturing | 2009 |
| Streem Ltd | Professional & scientific | 2022 |
| Streets Warehouse Limited | Real estate | 1998 |
| Strength & Performance Louth Ltd | Arts & recreation | 2014 |
| Striacroft Limited | Wholesale & retail | 1971 |
| Stubbs Property Developments Ltd | Construction | 2019 |
| Subsidium.Media Ltd | Information & communication | 2025 |
| Summit Presents Ltd | Hospitality | 2026 |
| Sunscorched Studios Limited | Information & communication | 2019 |
| Surge Electrical Estimating Limited | Construction | 2011 |
| Swagwear Ltd | Wholesale & retail | 2017 |
| Swirl and Spoon Ltd | Hospitality | 2026 |
| Sykes Heating & Plumbing Limited | Construction | 2019 |
| T & H Enterprises Limited | Administrative & support | 2006 |
| T & H Food Ltd | Hospitality | 2019 |
| T & H Strawson Ltd | Construction | 2016 |