| RGF Building Services Limited | Information & communication | 2025 |
| RHH Property Ltd | Real estate | 2019 |
| Rhodes Technologies Limited | Public administration | 2000 |
| Rhodium Resources Ltd. | Real estate | 2010 |
| RIB Vale Solutions Ltd | Construction | 2024 |
| Rich Display Ltd | Manufacturing | 2019 |
| Richard Lowden Ltd | Other services | 2013 |
| Richard Mukiibi Ltd | Health & social care | 2018 |
| Richmonds Holdings Limited | Financial services | 2019 |
| Rickmansworth Medical Ltd | Health & social care | 2012 |
| Rider Sale Ltd. | Construction | 1986 |
| Ridglea Limited | Wholesale & retail | 2016 |
| Ridgley Composites Ltd | Manufacturing | 2022 |
| Ringdale Surveys Limited | Professional & scientific | 2022 |
| Riskvane Ltd | Information & communication | 2026 |
| Riverboat Solutions Limited | Transport & logistics | 2007 |
| Riverrhee Consulting Limited | Professional & scientific | 2009 |
| RJ Foulston & Co Limited | Professional & scientific | 2014 |
| RJ Sol-Comm Solutions Ltd | Construction | 2025 |
| RJ2 Ltd | Wholesale & retail | 2024 |
| RJO Project Management Limited | Construction | 2015 |
| RKM Facilities Ltd | Construction | 2024 |
| RLC Optics Ltd | Professional & scientific | 2024 |
| Rljones Ltd | Construction | 2023 |
| RO Ruby Ltd | Wholesale & retail | 2011 |
| Roar Event Experiences Ltd | Hospitality | 2026 |
| Roban Builders Ltd | Construction | 2014 |
| Robert Dixon Developments Limited | Construction | 2015 |
| Robert Dixon Limited | Construction | 1948 |
| Robert James Systems Limited | Construction | 2005 |
| Robsport International Limited | Wholesale & retail | 1998 |
| Rocket and Cloud Ltd | Information & communication | 2003 |
| Rocky’S Retro’S Ltd | Wholesale & retail | 2022 |
| Rocol Estates Limited | Real estate | 2001 |
| Rodavis Solutions Limited | Professional & scientific | 2003 |
| Roger Hart Farms Limited | Agriculture & fishing | 1976 |
| Rogipo Capital Ltd | Professional & scientific | 2026 |
| Rojuemel Microcare Limited | Health & social care | 2023 |
| Rollins Farm Limited | Wholesale & retail | 2013 |
| Rollins Farm Trailers Limited | Manufacturing | 2025 |
| Roncam International Ltd | Wholesale & retail | 2021 |
| Ronkely Ltd | Extraterritorial | 2019 |
| Roofing Bro's Ltd | Construction | 2025 |
| Roroko Ltd | Professional & scientific | 2023 |
| Roseanna Lodge Limited | Extraterritorial | 2015 |
| Ross Morris Ltd | Real estate | 2007 |
| Rotol Limited | Manufacturing | 2017 |
| Rotuva Ltd | Information & communication | 2025 |
| Roundhedge Way Limited | Households | 1992 |
| Rowney Builders Limited | Construction | 1978 |
| Roysia Developments Limited | Arts & recreation | 2013 |
| Royston & District Community Transport | Transport & logistics | 2008 |
| Royston Accountants Ltd | Professional & scientific | 2018 |
| Royston Airport Services Ltd | Transport & logistics | 2016 |
| Royston Barbers Limited | Other services | 2014 |
| Royston BIN Cleaning Services Limited | Administrative & support | 2025 |
| Royston Cycles Limited | Wholesale & retail | 2008 |
| Royston Dental Care Ltd | Health & social care | 2013 |
| Royston Hand Car Wash Valeting Center Ltd | Administrative & support | 2019 |
| Royston Installations Ltd | Construction | 2020 |
| Royston Instruments Ltd | Manufacturing | 2024 |
| Royston Lunch Box Ltd | Hospitality | 2017 |
| Royston Nail Spa (KT) Limited | Other services | 2022 |
| Royston Old Schoolhouse CIC | Real estate | 2026 |
| Royston Pressure Washing Services Limited | Administrative & support | 2024 |
| Royston Spice Limited | Hospitality | 2022 |
| Royston Steak House and Grill Limited | Hospitality | 2024 |
| Royston Tandoori Express Ltd | Hospitality | 2021 |
| Royston Technology Ltd | Information & communication | 2012 |
| Royston Town Football Club Limited | Arts & recreation | 2022 |
| Royston Tyre Recycling Ltd | Water & waste | 2021 |
| Royston Veterinary Centre Ltd | Professional & scientific | 2007 |
| Roystonlondon Ltd | Wholesale & retail | 2021 |
| RSL 2025 Limited | Wholesale & retail | 2017 |
| Rtkfnet Limited | Agriculture & fishing | 2010 |
| RTR Scaffolding Services Ltd | Construction | 2018 |
| Rubycrest Limited | Construction | 1999 |
| Ruddells Carpentry & Building Ltd | Construction | 2013 |
| Rudolf Steiner Films Limited | Information & communication | 2011 |
| Rugged Removals Ltd | Transport & logistics | 2025 |
| Rumex Recruitment Ltd | Administrative & support | 2019 |
| Runcult Limited | Arts & recreation | 1987 |
| Rush Competitions Ltd | Arts & recreation | 2021 |
| RUW Art Consultancy Limited | Wholesale & retail | 2023 |
| RVR Utilities Ltd | Construction | 2025 |
| Ryans Plastering Limited | Construction | 2018 |
| Ryghost Limited | Professional & scientific | 2019 |
| S & D Hire Limited | Administrative & support | 2008 |
| S & J Tokely Limited | Real estate | 2019 |
| S & S Trading Limited | Other services | 2012 |
| S a E Stationery Ltd | Wholesale & retail | 2023 |
| S B Worldwide Innovations Limited | Manufacturing | 2016 |
| S J Tokely Limited | Wholesale & retail | 2011 |
| S K Plant Hire Ltd. | Construction | 1998 |
| S R College Ltd | Education | 2024 |
| S Wilks Sales Consultancy Ltd | Professional & scientific | 2023 |
| S&J Media Ltd | Information & communication | 2026 |
| S. K. Hyam Limited | Information & communication | 2001 |
| SA58ARU T8YWO Limited | Public administration | 2024 |
| Sabre Timber Limited | Wholesale & retail | 2004 |