| Scott Rail Limited | Construction | 2019 |
| SCP Warehouse Hub C.I.C. | Transport & logistics | 2024 |
| Screams Court Showbar Ltd | Arts & recreation | 2026 |
| Scrunch Kids Limited | Wholesale & retail | 2023 |
| SCT Surveys Limited | Professional & scientific | 2008 |
| Sculpt and Shape Ltd | Other services | 2024 |
| SDR Limited | Construction | 2002 |
| SDS Jointing Services Limited | Construction | 2013 |
| Sea Sky Pictures Ltd | Information & communication | 2025 |
| Sea View Design Ltd | Professional & scientific | 2015 |
| Seafood Corner House Limited | Wholesale & retail | 2024 |
| Seamer Site Holdings Limited | Real estate | 2025 |
| Sean a Carney Ltd | Administrative & support | 2018 |
| Seaton Carew Caravan & Container Storage Ltd | Transport & logistics | 2026 |
| Seaton Carew Motors Ltd | Wholesale & retail | 2022 |
| Seaton Slice Ltd | Hospitality | 2023 |
| Seaton Spice Ltd | Hospitality | 2019 |
| SEATON66 Ltd | Professional & scientific | 2023 |
| Seatoncarewholidaypark Ltd | Hospitality | 2024 |
| Seaview Installations Limited | Other services | 2014 |
| Secordit Intelligence Ltd | Information & communication | 2026 |
| Secure Steps Living Ltd | Manufacturing | 2025 |
| Sedgedene Estates Limited | Financial services | 1983 |
| Seed Homes Limited | Real estate | 2025 |
| Select Property Portfolio Limited | Real estate | 2017 |
| Self Storage Hartlepool Ltd | Transport & logistics | 2024 |
| Semper Exceed Ltd | Professional & scientific | 2025 |
| Seneca Global Energy Limited | Energy | 2012 |
| Seneca Investments and Developments Limited | Administrative & support | 2004 |
| Sentigral Limited | Information & communication | 2018 |
| Sentinel Wealth Management Ltd | Financial services | 2025 |
| Serenity Dreamweave Limited | Professional & scientific | 2025 |
| Sesw Electrical Ltd | Administrative & support | 2019 |
| SET Studios Facilities Ltd | Professional & scientific | 2021 |
| Setplay Media Ltd | Professional & scientific | 2026 |
| Sewell Holding Group Ltd | Financial services | 2024 |
| Seymour (Construction & Property Maintenance) Limited | Construction | 2009 |
| Seymour (Plant & Equipment) Ltd | Administrative & support | 2016 |
| Seymour Group Holding Company (North East) Limited | Financial services | 2026 |
| Seymour House (Hartlepool) Limited | Health & social care | 2002 |
| SF Rope Access Services Ltd | Mining & quarrying | 2021 |
| Sfreya Ltd | Health & social care | 2023 |
| SG Francis Limited | Professional & scientific | 2015 |
| SGT Mechanical Services Ltd. | Construction | 2016 |
| Shadowtrac Ltd | Administrative & support | 2026 |
| Shadsubsidiary UK Ltd | Wholesale & retail | 2026 |
| Shaheen Medical Services Limited | Financial services | 2001 |
| Shanakee Media Limited | Information & communication | 2015 |
| Shapella Blinds Limited | Manufacturing | 2014 |
| Shapers (N.E.) Ltd | Other services | 2024 |
| Shapool Engineering & Design Ltd | Professional & scientific | 2020 |
| Sharjarin Ltd | Real estate | 2023 |
| Sharpley Leisure Ltd | Arts & recreation | 2009 |
| Sheraton Bespoke Joinery Limited | Manufacturing | 2019 |
| Sheraton Design & Build Limited | Professional & scientific | 2001 |
| Sheraton Group Limited | Financial services | 2019 |
| Sherlocks Vintage Ltd | Wholesale & retail | 2022 |
| SHH Instrument Services Ltd | Professional & scientific | 2024 |
| Shinnyhome Cleaning Services Ltd | Administrative & support | 2026 |
| Shiny Bee's Cleaning Company Ltd | Administrative & support | 2026 |
| Shipper Fabrication Limited | Professional & scientific | 2026 |
| Shoot on Site Films Limited | Information & communication | 2020 |
| Shoreline Competitions Ltd | Arts & recreation | 2025 |
| Shoreline Fire Compliance Limited | Professional & scientific | 2023 |
| Shree Sairam Builders & Developers Limited | Construction | 2018 |
| SIA Security Training Limited | Education | 2023 |
| Siam TS24 Ltd | Hospitality | 2025 |
| Sight Link Solutions Ltd | Professional & scientific | 2025 |
| Signature Skin and Aesthetics Limited | Health & social care | 2023 |
| Silent Steppers Ltd | Arts & recreation | 2025 |
| Silver Fern MT99 Ltd | Agriculture & fishing | 2022 |
| Silverstar Takeaway Limited | Hospitality | 2002 |
| Silvertrail Ltd | Extraterritorial | 2026 |
| Silverwood Technical Services Ltd | Professional & scientific | 2025 |
| Simba.Fit Ltd | Wholesale & retail | 2019 |
| Sink OR Swim Ltd | Hospitality | 2026 |
| Sios Property Ltd | Financial services | 2022 |
| SIP & Blush Ltd | Hospitality | 2024 |
| Site Crews Ltd | Administrative & support | 2025 |
| Sitewide Solutions Limited | Construction | 2024 |
| Siwel Ltd | Arts & recreation | 2025 |
| SIX West Ventures Limited | Professional & scientific | 2023 |
| SJB Civils Ltd | Construction | 2026 |
| SJD Construction Services Limited | Construction | 2018 |
| SJR Architectural & Interior Designers Ltd | Professional & scientific | 2018 |
| SK & LC Services Limited | Professional & scientific | 2019 |
| SK Safety Systems Limited | Construction | 2025 |
| Sk:Ulpt Clinic Ltd | Other services | 2024 |
| Skatiebeau Investments Limited | Financial services | 2026 |
| SKH Catering Ltd | Hospitality | 2025 |
| Skol Catering Limited | Hospitality | 2025 |
| Sky Blue Ocean Media Ltd | Administrative & support | 2021 |
| Sky Nails and Beauty 93 Limited | Other services | 2021 |
| Skye W Ltd | Professional & scientific | 2026 |
| Skyland Limited | Health & social care | 2016 |
| SL (Contracts) Ltd | Professional & scientific | 2009 |
| SL Electrics North East Ltd | Construction | 2023 |
| Slch Freehold Ltd | Households | 2022 |
| Slev's Residential Properties Ltd | Real estate | 2025 |
| SLS Engineering and Technical Services Limited | Professional & scientific | 2014 |