| SHS Utility Ltd | Wholesale & retail | 2012 |
| Shugs & SON Ltd | Construction | 2000 |
| Shuja Limited | Information & communication | 2013 |
| Shutter & Saddle Ltd | Professional & scientific | 2026 |
| Shutter Solutions Limited | Construction | 2020 |
| Shutters 4 Bedford Ltd | Wholesale & retail | 2025 |
| Shuttle Logistics Limited | Transport & logistics | 2021 |
| Shybee’S Ltd | Wholesale & retail | 2026 |
| Shyno Property Ltd | Real estate | 2020 |
| Shyres Rural Limited | Professional & scientific | 2008 |
| SI Dablieu Ltd | Health & social care | 2018 |
| SI Waterscapes Ltd | Administrative & support | 2019 |
| SIA (Gravenhurst) Ltd | Professional & scientific | 2023 |
| SIA (Hitchin) Ltd | Professional & scientific | 2023 |
| Siam Eagles Thai Boxing Ltd | Arts & recreation | 2021 |
| Siam Heaven Limited | Hospitality | 2019 |
| Sian Peer Limited | Professional & scientific | 2022 |
| Sias Consulting Ltd | Professional & scientific | 2017 |
| Sibili Limited | Wholesale & retail | 2015 |
| Sibley Consultants Ltd | Professional & scientific | 2013 |
| Sibq Limited | Information & communication | 2010 |
| Sibq Sixteen Ltd | Real estate | 2016 |
| Sicovosec Ltd | Administrative & support | 2024 |
| Sidewinder Events Limited | Arts & recreation | 2020 |
| Sidewinder Festival Limited | Arts & recreation | 2023 |
| Sidham Holding Ltd | Financial services | 2026 |
| Sidham Trading Limited | Real estate | 2002 |
| Sidhu Consultancy Services Limited | Professional & scientific | 2015 |
| Sids DIY Ltd | Wholesale & retail | 2026 |
| Siegel Ltd | Construction | 2012 |
| Siem Integrated Services Limited | Other services | 2025 |
| Sienna and Leonor Limited | Administrative & support | 2022 |
| Sienna Polish & Shine Ltd | Administrative & support | 2025 |
| Sifdale Ltd | Manufacturing | 2018 |
| Sight Concern Bedfordshire | Health & social care | 2006 |
| Sigma Plumbing & Heating Ltd | Construction | 2022 |
| Sigma Professionals Ltd | Other services | 2025 |
| Sigma Safe UK Ltd | Wholesale & retail | 2025 |
| Sigmasoft Technical Services Limited | Professional & scientific | 2010 |
| Sigmavend Limited | Extraterritorial | 2015 |
| Sign Language Limited | Manufacturing | 2002 |
| Signature Academy Limited | Other services | 2014 |
| Signature Clearance Ltd | Water & waste | 2026 |
| Signature Health Ltd | Health & social care | 2023 |
| Signature Sales and Lettings Ltd | Real estate | 2023 |
| Signed Boutique Limited | Wholesale & retail | 2016 |
| Signify Research Corporation Limited | Financial services | 2024 |
| Signify Research Holding Limited | Financial services | 2024 |
| Signify Research Limited | Professional & scientific | 2016 |
| Sigtrans & Logistics Ltd | Transport & logistics | 2026 |
| Sikhana Seekho Limited | Education | 2022 |
| Silas Group Limited | Financial services | 2006 |
| Silbase Limited | Transport & logistics | 2001 |
| Silicone Fabrication Services Limited | Manufacturing | 1997 |
| Siloam Health Care Ltd | Health & social care | 2017 |
| Silous Ltd | Information & communication | 2017 |
| Silsoe Classic and Modern Limited | Manufacturing | 2019 |
| Silsoe Newsagents Limited | Wholesale & retail | 2007 |
| Silsoe Odours Limited | Professional & scientific | 2005 |
| Silsoe Prestige Motors Ltd | Wholesale & retail | 2020 |
| Silsoe Solutions Limited | Administrative & support | 2003 |
| Silsoe Spray Applications Unit Limited | Professional & scientific | 2015 |
| Silva Transport Services Ltd | Transport & logistics | 2016 |
| Silvaeculture Limited | Professional & scientific | 2013 |
| Silver by Prems Ltd | Wholesale & retail | 2020 |
| Silver Cloud Hypnotherapy Ltd | Other services | 2022 |
| Silver Faces Dance Collective CIC | Arts & recreation | 2025 |
| Silver Reed (2000) Limited | Wholesale & retail | 1990 |
| Silver Reed UK Limited | Wholesale & retail | 2009 |
| Silver Spinney LLP | | 2025 |
| Silverlight Software Consulting Limited | Information & communication | 2011 |
| Silverline Assets Limited | Real estate | 2023 |
| Silvermim Ltd | Wholesale & retail | 2020 |
| Silveroak Financial Services Limited | Financial services | 2020 |
| Silverstone Vehicle Movements Ltd | Transport & logistics | 2024 |
| Silvertex Balloons Ltd | Wholesale & retail | 2021 |
| Simade Healthcare Ltd | Health & social care | 2019 |
| Simas Accounting Services Limited | Professional & scientific | 2017 |
| Simba Facilities Ltd | Administrative & support | 2019 |
| Simi & Lola Ltd | Wholesale & retail | 2012 |
| Simkey Mortgages Cranfield Limited | Real estate | 2023 |
| Simkey Mortgages Limited | Financial services | 2020 |
| Simmit Trades Ltd | Wholesale & retail | 2026 |
| Simmons Industries Ltd | Wholesale & retail | 2024 |
| Simmons Soil Management Solutions Ltd | Professional & scientific | 2024 |
| Simon DAW Consulting Ltd | Professional & scientific | 2026 |
| Simon Says Sales Ltd | Other services | 2018 |
| Simon&Co Property Maintenance Ltd | Construction | 2025 |
| Simple Inc Limited | Professional & scientific | 2016 |
| Simplee Properties Limited | Real estate | 2023 |
| Simplee Scaffolding Limited | Construction | 2014 |
| Simplee Scaffolding Services Limited | Construction | 2023 |
| Simplexity Limited | Professional & scientific | 1999 |
| Simplified Systems Consulting Ltd | Information & communication | 2021 |
| Simply Flooring Experts Limited | Construction | 2011 |
| Simply Gadgets Ltd | Wholesale & retail | 2014 |
| Simply Horse (Lilley) Ltd | Administrative & support | 2024 |
| Simply Name Change Ltd | Information & communication | 2025 |
| Simply Nice Stuff Ltd | Wholesale & retail | 2025 |
| Simply Property Rentals Limited | Real estate | 2021 |