| Stairhill Architecture Ltd | Professional & scientific | 2015 |
| Stairhill Developments Limited | Construction | 2005 |
| Stalwart Catering Equipment Ltd | Hospitality | 2018 |
| Stanfex Logistics LP | | 2014 |
| Stanlaidh Limited | Administrative & support | 2022 |
| Star Signs Installation & Maintenance Ltd | Construction | 2013 |
| Starcollector Limited | Information & communication | 2012 |
| Starfish Leisure Ltd | Other services | 2015 |
| Starks Engineering Services Ltd | Professional & scientific | 2012 |
| Station Enterprises Ltd | Wholesale & retail | 2013 |
| Statz Ltd | Information & communication | 2021 |
| Stefano Business LP | | 2014 |
| Stephen Bloy Brickwork Ltd | Construction | 2025 |
| Stephen Caffyn Design Ltd | Professional & scientific | 2024 |
| Stephen Mccormick Pharmacies Limited | Wholesale & retail | 2015 |
| Sterlclean Ltd | Professional & scientific | 2016 |
| Steven Dick Properties Limited | Real estate | 2021 |
| Steven Gray Plumbing and Heating Ltd | Construction | 2020 |
| Steven Wallace Electrical Ltd | Energy | 2018 |
| Stevenson Construction Contracts Limited | Administrative & support | 2016 |
| Stevie's Structural Repairs Limited | Manufacturing | 2025 |
| Stewart ACR Ltd | Energy | 2018 |
| Stewart Gilmour & Co. (2024) Limited | Professional & scientific | 2024 |
| Stewart Gilmour & Co. Limited | Professional & scientific | 2018 |
| Stewarts Fruit and VEG Limited | Wholesale & retail | 2017 |
| STF Ayrshire Services Ltd | Administrative & support | 2025 |
| Stig Plant Ltd | Wholesale & retail | 2023 |
| Stigma Consult LP | | 2014 |
| Stimler Trade LP | | 2016 |
| Stitch in Time AYR Ltd | Extraterritorial | 2017 |
| STJ Limited | Hospitality | 2022 |
| Stonedale Residential Limited | Real estate | 2019 |
| Stonedale Securities Limited | Real estate | 2003 |
| Stonefield (Ayrshire) Limited | Real estate | 2008 |
| Stonefield (Group) Limited | Financial services | 2022 |
| Stonefield Financial Services Ltd | Financial services | 2012 |
| Stonefield Landscapes Ltd | Administrative & support | 2026 |
| Stonefield Mortgages Ltd | Financial services | 2024 |
| Stonehouse Development Agency Ltd | Real estate | 2015 |
| Storage Solutions Ayrshire Ltd | Transport & logistics | 2022 |
| Storeayr Ltd | Transport & logistics | 2025 |
| Storie (Argyll) Limited | Water & waste | 1968 |
| Storm 360 Limited | Information & communication | 2012 |
| Storm Art Ltd | Arts & recreation | 2024 |
| Strada Environmental Limited | Professional & scientific | 2014 |
| Strada Holdings Ltd | Financial services | 2020 |
| Strada Properties Ltd | Real estate | 2020 |
| Straight 2 Trade Double Glazing Ltd | Construction | 2023 |
| Strathayr Financial Services LLP | | 2001 |
| Strathdoon Project Consultants Ltd. | Professional & scientific | 2021 |
| Stratical Consultants Ltd. | Professional & scientific | 2013 |
| Stream Mobile Limited | Transport & logistics | 2026 |
| Streetworkout.Pro LP | | 2014 |
| Strictly Bridal Limited | Wholesale & retail | 2019 |
| Strongroom AYR Limited | Hospitality | 2013 |
| STUDIO20THREE Ltd | Professional & scientific | 2020 |
| STUDIO893 Ltd | Arts & recreation | 2026 |
| Sturdy Property Ltd | Real estate | 2022 |
| Style Builders Group Ltd | Construction | 2018 |
| Styled by AMY M Ltd | Other services | 2025 |
| SUB SOL Engineering Ltd | Professional & scientific | 2022 |
| Substation Construction Ltd | Energy | 2022 |
| Sugar N Slice (Scotland) Ltd | Wholesale & retail | 2017 |
| Sugar Spuds and Smiles Ltd | Hospitality | 2025 |
| Suite Fifteen Limited | Information & communication | 2019 |
| Summerbrooke Developments Ltd | Real estate | 2020 |
| Summers Aviation Safety Training Ltd | Education | 2025 |
| Summers HAY Investments Limited | Real estate | 2023 |
| Sunderland of Scotland Limited | Wholesale & retail | 1966 |
| Sunland Global LP | | 2014 |
| Sunsations Ltd | Other services | 2011 |
| Super Squid Limited | Administrative & support | 2024 |
| Superdata UK Ltd | Information & communication | 2005 |
| Superior MAC Ltd | Wholesale & retail | 2025 |
| Superstar Software Limited | Information & communication | 2022 |
| Supportact Ltd | Professional & scientific | 2025 |
| Surface Air Technologies Ltd | Administrative & support | 2021 |
| Susan Kirk Hair Ltd | Other services | 2019 |
| Suzie H Rentals Ltd | Real estate | 2026 |
| SW Timber Harvesting Limited | Agriculture & fishing | 2017 |
| Sweatfest Limited | Other services | 2026 |
| Sweet Justice Limited | Real estate | 2018 |
| Swimple Ltd | Wholesale & retail | 2021 |
| Swsr Ltd | Administrative & support | 2026 |
| Symington Developments Limited | Construction | 2002 |
| Systemic Education Ltd | Education | 2020 |
| Systems Insight Limited | Information & communication | 1987 |
| T a Walker Enterprise Limited | Real estate | 2022 |
| T H Dalling Limited | Wholesale & retail | 2015 |
| T J Walker Holdings Limited | Real estate | 2022 |
| T Walsh Contracts Ltd | Manufacturing | 2020 |
| T Walsh Property Ltd | Real estate | 2023 |
| T.J. Walker (International) Limited | Real estate | 1996 |
| T.J.Walker (Scotland) Limited | Real estate | 1987 |
| Taigh a Chluarain Ltd | Real estate | 2019 |
| Tait Paradigms Ltd | Arts & recreation | 2020 |
| Talhavirk Ltd | Wholesale & retail | 2025 |
| Tall Poppy Consultancy Limited | Professional & scientific | 2011 |
| Tamsbrig Store Ltd | Wholesale & retail | 2021 |
| Tanit Tanning Ltd | Wholesale & retail | 2026 |