| React Access Ltd | Professional & scientific | 2018 |
| REACTIV8 the Nation Limited | Real estate | 2011 |
| Reactive Doors Ltd | Construction | 2009 |
| Reactive Rentals Ltd | Administrative & support | 2022 |
| REACTIVE8 the Nation CIC | Education | 2013 |
| Read & Associates Ltd | Professional & scientific | 2022 |
| Read Analytics Ltd | Administrative & support | 2019 |
| Read Photography Limited | Professional & scientific | 2013 |
| Reading Shoulder Unit Limited | Professional & scientific | 2010 |
| Ready 2 Rethink Ltd | Professional & scientific | 2023 |
| Reaffirm Ltd | Information & communication | 2024 |
| Real Cash Monopoly Limited | Real estate | 2019 |
| Real Estate Giants Limited | Real estate | 2018 |
| Real Expedite Ltd | Professional & scientific | 2024 |
| Real Intelligence Academy Limited | Administrative & support | 2018 |
| Real Livin Ltd | Real estate | 2022 |
| Real Rents Property Management Ltd | Real estate | 2013 |
| Real World Personal Training Limited | Arts & recreation | 2013 |
| Real-Time Training (UK) Ltd | Information & communication | 2013 |
| Realcare + Limited | Administrative & support | 2011 |
| Reality Housing CIC | Hospitality | 2020 |
| Realization Limited | Professional & scientific | 2003 |
| Really Flexible Mortgages Limited | Real estate | 2000 |
| Realm of the Possible Limited | Professional & scientific | 2020 |
| Realty Reserves Limited | Real estate | 2023 |
| Reay Core Ltd | Wholesale & retail | 2025 |
| Rebel Demon Ltd | Wholesale & retail | 2019 |
| Rebellion Fitness Ltd | Health & social care | 2012 |
| Reboxd Limited | Construction | 2022 |
| Reboxd Market Limited | Construction | 2023 |
| REC 2 TEC Diving Limited | Arts & recreation | 2015 |
| REC2TEC Diving Milton Keynes Ltd | Arts & recreation | 2022 |
| Recall Support Services Limited | Administrative & support | 2003 |
| Receiver Records Limited | Arts & recreation | 1980 |
| Recept Consulting Limited | Real estate | 2010 |
| Reclaim Environmental (Holdings) Limited | Water & waste | 2001 |
| Reclaim Environmental Limited | Water & waste | 1947 |
| Reclaimed and Renewed Ltd | Manufacturing | 2024 |
| Recognex Limited | Information & communication | 2013 |
| Recognise Limited | Manufacturing | 2009 |
| Recognition Express Limited | Professional & scientific | 1979 |
| Recognize Hair Limited | Other services | 2017 |
| Reconcile Network Ltd | Other services | 2024 |
| Recordflow Ltd | Information & communication | 2015 |
| Recovery and Services Ltd | Transport & logistics | 2023 |
| Recovery Connect Ltd | Transport & logistics | 2023 |
| Recovery Homes C.I.C. | Real estate | 2014 |
| Recovery Housing Holdings Limited | Hospitality | 2014 |
| Recovery Mind Limited | Wholesale & retail | 2018 |
| Recreāre Bespoke Tattooing Limited | Arts & recreation | 2025 |
| Recruit Core Limited | Administrative & support | 2013 |
| Recruit Resources Limited | Information & communication | 2023 |
| Recruit Xperts Limited | Administrative & support | 2018 |
| Recruitment Express Limited | Administrative & support | 1998 |
| Rectangle Red Limited | Professional & scientific | 2006 |
| Rectangle Technologies Limited | Information & communication | 2026 |
| Rectella Property Limited | Wholesale & retail | 2020 |
| Rectory Self-Build Limited | | 1982 |
| Recurrism Ltd | Professional & scientific | 2018 |
| Recycle My INK Limited | Water & waste | 2025 |
| Recycled Syllabits Ltd | Wholesale & retail | 2024 |
| Red & Blue Mechanical Limited | Construction | 2014 |
| Red Black White Line Ltd | Construction | 2016 |
| Red Door Lettings Ltd | Real estate | 2020 |
| Red Empire 3 (UK) Ltd | Other services | 2014 |
| Red Flame MK Ltd | Construction | 2018 |
| Red HAT Rigging Ltd | Construction | 2023 |
| Red Head Productions Ltd | Professional & scientific | 2007 |
| Red Hill Farming Company Limited | Agriculture & fishing | 2004 |
| Red Kite International Limited | Education | 2025 |
| Red Kite Rentals Limited | Real estate | 2017 |
| Red Label Consultancy Limited | Professional & scientific | 2013 |
| Red Letter Box Limited | Professional & scientific | 2014 |
| Red Line Europe Limited | Construction | 2012 |
| Red Line Pharmacovigilance Limited | Health & social care | 2010 |
| Red Maple Homes Ltd | Real estate | 2025 |
| Red Marshall Ltd | Information & communication | 2009 |
| Red Nation Limited | Wholesale & retail | 2025 |
| Red Oak Group Ltd | Administrative & support | 2015 |
| Red Oak Valuations Limited | Professional & scientific | 2026 |
| Red Pepper (MK) Catering Ltd | Hospitality | 2023 |
| Red Photon Ltd | Professional & scientific | 2016 |
| Red Physiotherapy Franchising Ltd | Administrative & support | 2024 |
| Red Physiotherapy Ltd | Health & social care | 2021 |
| Red Planet Consulting Ltd | Information & communication | 2005 |
| Red Recovery Limited | Wholesale & retail | 2025 |
| Red Rock London Limited | Construction | 2015 |
| Red Rose Programming Limited | Information & communication | 1994 |
| Red Shutterfly Media Limited | Wholesale & retail | 2017 |
| Red Squirrel Films Ltd | Information & communication | 2012 |
| Red Sun Solutions Limited | Professional & scientific | 2011 |
| Redblueav Properties Limited | Real estate | 2024 |
| Redboon Consultancy Services Limited | Information & communication | 2015 |
| Redbridge Online Services Limited | Wholesale & retail | 2025 |
| Redcar 64 Limited | Real estate | 2025 |
| Redclean XT Ltd | Administrative & support | 2025 |
| Redcoombe Limited | Construction | 2012 |
| Redcote Manor Limited | Professional & scientific | 2020 |
| Reddi Tech Limited | Information & communication | 2025 |
| Redding Estates Ltd | Real estate | 2025 |