| Reflect NDT Ltd | Professional & scientific | 2018 |
| Regal Motors (Ashington) Limited | Real estate | 1978 |
| Reheat (Renewable Technologies) Heat Services Limited | Other services | 2023 |
| Reheat (Renewable Technologies) Limited | Other services | 2011 |
| Reiver Consulting Limited | Professional & scientific | 2025 |
| Reivertech Limited | Information & communication | 2011 |
| Reliance Reliability Systems Ltd | Professional & scientific | 2019 |
| Renewables North East Ltd | Professional & scientific | 2015 |
| Research ID Ltd | Other services | 2023 |
| Resource Refugees Ltd | Information & communication | 2022 |
| Retail Therapy Ltd | Other services | 2011 |
| Revalute Limited | Information & communication | 2024 |
| Rhino Mobile N Vapes Ltd | Wholesale & retail | 2025 |
| Richard Aynsley Limited | Transport & logistics | 2018 |
| Richard Brown and Partners Limited | Real estate | 2025 |
| RJC Retail Limited | Wholesale & retail | 2013 |
| RJD Wind Ltd | Construction | 2023 |
| Robert Gascoyne Consulting Ltd | Professional & scientific | 2004 |
| Robson Portfolio Ltd. | Wholesale & retail | 2023 |
| Rock Farms Limited | Agriculture & fishing | 1957 |
| Rossco Ventures Ltd | Real estate | 2025 |
| Rothbury Motors Limited | Transport & logistics | 1973 |
| Rothco Independent Mortgages Ltd | Administrative & support | 2002 |
| Roxbro Limited | Real estate | 2020 |
| RW Athey Limited | Construction | 2005 |
| Ryehill Community Ventures | Health & social care | 2020 |
| S & J Parsons Limited | Professional & scientific | 2023 |
| S James Martin Enterprises Limited | Information & communication | 2012 |
| S Rowntree Associates Limited | Professional & scientific | 2007 |
| S T Watson (Builders) Ltd | Construction | 2019 |
| Salam Sounds CIC | Wholesale & retail | 2025 |
| Salt and Co. Ltd | Manufacturing | 2022 |
| Sapphire Coaching Limited | Professional & scientific | 2010 |
| Sarah Jane Brown Limited | Arts & recreation | 2002 |
| Saray Turkish Grill House Ltd | Hospitality | 2020 |
| Satya Insights Ltd | Extraterritorial | 2024 |
| Schiavetta Consulting Limited | Professional & scientific | 2009 |
| Schofield Dyers & Finishers Limited | Manufacturing | 2007 |
| Schooner (Alnmouth) Limited | Hospitality | 2016 |
| Schooner Hotel Limited | Hospitality | 2024 |
| Scottalbion Holdings Limited | Hospitality | 2021 |
| Scout Hill Management Company Limited | Households | 2021 |
| Scrub Sports Ltd | Wholesale & retail | 2023 |
| Sea and Salt Ltd | Hospitality | 2025 |
| Seafield Catering Ltd | Hospitality | 2026 |
| Seamer Station Limited | Extraterritorial | 2009 |
| Seaton Park Caravans Ltd | Hospitality | 2025 |
| Seaton Point Steading Management Company Limited | Households | 2023 |
| Self Service Coffee Co Ltd | Hospitality | 2025 |
| Seyon Services Ltd | Wholesale & retail | 2023 |
| SGO Autos Ltd | Wholesale & retail | 2025 |
| SGR Technical Services Limited | Arts & recreation | 2011 |
| Shampaws and SET Ltd | Extraterritorial | 2023 |
| Shangsus Pony Trecking Ltd | Agriculture & fishing | 2022 |
| Shapwells Developments Limited | Agriculture & fishing | 1952 |
| Shastik Ltd | Wholesale & retail | 2025 |
| Shilbottle Community Hall Limited | Arts & recreation | 2009 |
| Shilbottle Friendly Frogs Limited | Education | 2009 |
| Shiny White Stuff Ltd | Wholesale & retail | 2024 |
| Shoreside Shepard Huts Ltd | Hospitality | 2015 |
| Sidbie's Brew Co Ltd | Manufacturing | 2025 |
| Simpli Planning Ltd | Professional & scientific | 2023 |
| Simpli Residential Limited | Real estate | 2022 |
| Simply Coastal Trading Ltd | Hospitality | 2018 |
| Simpson Services (Painters & Decorator) Ltd | Construction | 2024 |
| Sion Leisure Limited | Hospitality | 2025 |
| SIR Humphrey Wakefield + Partners Limited | Administrative & support | 1978 |
| Sjcinspections Limited | Professional & scientific | 2012 |
| SJF Engineering Limited | Professional & scientific | 2011 |
| SK Diner Limited | Hospitality | 2023 |
| SK Motorcare Ltd | Wholesale & retail | 2026 |
| Skreened Ltd | Wholesale & retail | 2022 |
| SL Consulting and Design Ltd | Wholesale & retail | 2020 |
| Slate Hall Riding Centre Ltd | Agriculture & fishing | 2019 |
| Small World Cafe (Hexham) Ltd | Hospitality | 2024 |
| Smiths Accountants & Tax Advisers Ltd | Professional & scientific | 2014 |
| SMJ Tyre Services Ltd | Other services | 2009 |
| Smtj Joinery Ltd | Construction | 2020 |
| Snotty Nosed Caravan Club Ltd | Real estate | 2024 |
| SNS Ashington Limited | Real estate | 2026 |
| SNS Flips Ltd | Real estate | 2020 |
| SNS Traders Ltd | Wholesale & retail | 2020 |
| Social Initiatives Limited | Professional & scientific | 2024 |
| Sonnet.Restaurant Limited | Hospitality | 2023 |
| South END Plumbing and Heating Ltd | Construction | 2002 |
| South Road Tyres Limited | Wholesale & retail | 2001 |
| Spikes Marketing Associates Limited | Professional & scientific | 2019 |
| Spirit of Northumberland Limited | Wholesale & retail | 2011 |
| Splended Ltd | Hospitality | 2024 |
| Springwood Racing Ltd | Arts & recreation | 2021 |
| Squelch Wellies Limited | Wholesale & retail | 2019 |
| Stable Yard Landscapes Ltd | Construction | 2011 |
| Stamford Farms Ltd | Agriculture & fishing | 2012 |
| Star Pizza (Shilbottle) Limited | Wholesale & retail | 2023 |
| Stark Global Training Solutions Limited | Administrative & support | 2013 |
| Status Motor Company Ltd | Manufacturing | 2025 |
| Step Forward Training & Coaching Ltd | Education | 2013 |
| Stephen Willcox Builder Limited | Construction | 2003 |
| Stocksmith & Co Ltd | Professional & scientific | 2016 |
| Stoker Village Farm Ltd | Hospitality | 2001 |