| RBW Diagnostics Limited | Health & social care | 2026 |
| RC Bond Holdings Limited | Financial services | 2014 |
| RC Deals Limited | Wholesale & retail | 2019 |
| RC Electronics Industry Co., Ltd. | Wholesale & retail | 2025 |
| RC Intelligence Limited | Real estate | 2023 |
| RC Motorsport Ltd | Manufacturing | 2024 |
| RCB Bonds PLC | Financial services | 2014 |
| Rcexl Electronics Co., Ltd. | Wholesale & retail | 2024 |
| RCG Construction Limited | Construction | 2009 |
| RCM Property Developments Limited | Construction | 2015 |
| Rcma Services (UK) Limited | Administrative & support | 2010 |
| RCR Metallurgical Limited | Professional & scientific | 2024 |
| RCS & Groundworks Ltd | Construction | 2026 |
| Rcuk Advisory Limited | Financial services | 2021 |
| RD Executive Properties Limited | Construction | 2021 |
| RD World Company Limited | Extraterritorial | 2024 |
| RD1 Consulting Limited | Health & social care | 2022 |
| RDC Tech UK Ltd | Professional & scientific | 2024 |
| Rden Consulting Limited | Professional & scientific | 2026 |
| RDP Life Sciences Limited | Professional & scientific | 2017 |
| Rdxn Ltd | Manufacturing | 2025 |
| Re-Born Flooring Limited | Construction | 2016 |
| Re:Fresh Cambridge Ltd | Other services | 2018 |
| Reach Cambridge Ltd | Administrative & support | 2004 |
| Reach Fair Cambridgeshire CIC | Administrative & support | 2023 |
| Reading Online Limited | Education | 2022 |
| Reading Retreat Ltd | Other services | 2019 |
| Real Aero Consulting Ltd | Professional & scientific | 2025 |
| Real Asset Capital Ltd | Real estate | 2018 |
| Real Bridge Games Ltd | Information & communication | 2020 |
| Real Estate Advisory Limited | Financial services | 2022 |
| Real Estate Management (REM) Ltd | Extraterritorial | 2022 |
| Real Export Group International Limited | Wholesale & retail | 2019 |
| Real Greens Ltd | Arts & recreation | 2026 |
| Real Italian Food Limited | Wholesale & retail | 2014 |
| Realife Trust | Health & social care | 2000 |
| Realising the Potential Ltd | Information & communication | 2016 |
| Reality Optics Limited | Professional & scientific | 2023 |
| Realled Limited | Extraterritorial | 2020 |
| Really Responsible Limited | Professional & scientific | 2010 |
| Realnet Limited | Information & communication | 1998 |
| Realvnc Limited | Information & communication | 2002 |
| Realwood Products Limited | Wholesale & retail | 2017 |
| Reanglia CIC | Professional & scientific | 2026 |
| Reardon & Co Limited | Professional & scientific | 1995 |
| Reatech Solutions Ltd. | Information & communication | 2015 |
| Rebecca Orde Ltd | Professional & scientific | 2010 |
| Rebel Retail Limited | Extraterritorial | 2026 |
| Rebel Strategic Assets Holding Ltd | Financial services | 2026 |
| Rebelle Group Limited | Financial services | 2025 |
| Rebmarc Developments Ltd | Extraterritorial | 2021 |
| Rebmarc Limited | Other services | 1972 |
| Rebtec Limited | Administrative & support | 2010 |
| Rebus Capital Management Limited | Financial services | 2017 |
| Rebus Consulting Limited | Professional & scientific | 2019 |
| Rebus Investment Limited | Financial services | 2018 |
| Rebus Real Estate Limited | Real estate | 2018 |
| Recardo Auto Repairs Limited | Wholesale & retail | 2025 |
| Recipe Limited | Information & communication | 2016 |
| Reclinker Ltd | Professional & scientific | 2022 |
| Recoheat Ltd | Manufacturing | 2020 |
| Recon Consultancy Limited | Professional & scientific | 2018 |
| Recon Consultations Limited | Professional & scientific | 2025 |
| Reconfitnessuk Ltd | Health & social care | 2026 |
| Recovery Hub (Cambridge) Community Interest Company | Hospitality | 2016 |
| Rectory Farm (Pampisford) Limited | Agriculture & fishing | 1954 |
| Rectory Farm Thriplow LLP | | 2023 |
| Rectory Farm Thriplow Residents Management Company Limited | Households | 2025 |
| Rectory Property Consulting Limited | Professional & scientific | 2015 |
| Recycle BIO Limited | Professional & scientific | 2023 |
| Red ASH Limited | Professional & scientific | 2016 |
| Red Balloon Educational Trust | Education | 2005 |
| Red Balloon of the Air | Education | 2010 |
| Red Box Retail Ltd | Wholesale & retail | 2012 |
| Red Building Manchester (UK) Ltd | Real estate | 2022 |
| Red Chilli Cambridgeshire Limited | Hospitality | 2026 |
| Red Cloud Consultancy Limited | Information & communication | 2017 |
| Red Flame WOK Ltd | Hospitality | 2025 |
| Red FOX Cycling Limited | Administrative & support | 2018 |
| Red Gate Software Group Limited | Information & communication | 2016 |
| Red Gate Software Limited | Information & communication | 1999 |
| Red Graphic Cambridge Ltd | Professional & scientific | 2004 |
| Red Horse Recruitment Ltd | Administrative & support | 2024 |
| Red Hot Ltd | Administrative & support | 2023 |
| Red House Developments (Histon) Ltd | Real estate | 2024 |
| Red House Ripon Management Ltd | Real estate | 2016 |
| Red Kite (MK) Ltd | Financial services | 2024 |
| Red Leaf Investments Ltd | Real estate | 2021 |
| Red Meadow Ltd | Education | 2024 |
| Red Monster Print Ltd | Manufacturing | 2012 |
| Red Next Ltd | Wholesale & retail | 2025 |
| Red Panda Property Lets Limited | Real estate | 2022 |
| Red Scarf Services Ltd | Extraterritorial | 2020 |
| Red Sea Investments Limited | Financial services | 2024 |
| Red Sector Energy Chemical Group Co., Ltd | Extraterritorial | 2019 |
| Red Sky Construction Limited | Construction | 2017 |
| Red Sky Taverns Ltd | Hospitality | 2021 |
| Red Star Search Limited | Administrative & support | 2020 |
| Red Together Ltd | Other services | 2018 |
| Red Web Cambridge Limited | Information & communication | 2025 |