| Q-Zam Group Limited | Transport & logistics | 2015 |
| Q.E.S. Limited | Manufacturing | 1990 |
| Qabid Solutions Limited | Information & communication | 2016 |
| Qarc Limited | Administrative & support | 2008 |
| QC Havencare Ltd | Health & social care | 2025 |
| QC Property Group Ltd | Real estate | 2021 |
| QED Management Systems Limited | Professional & scientific | 2009 |
| QEV Solutions Limited | Professional & scientific | 2021 |
| QIP Vortex Limited | Extraterritorial | 2025 |
| Qiss Ltd | Information & communication | 2024 |
| Qnipay Limited | Administrative & support | 2026 |
| QS Courier Ltd | Transport & logistics | 2022 |
| Quad Advisory Limited | Professional & scientific | 2014 |
| Quadrangle Development Limited | Construction | 2007 |
| Quainton Carpets Ltd | Administrative & support | 2018 |
| Quainton Dairy Limited | Agriculture & fishing | 1972 |
| Quainton Railway Company Limited | Extraterritorial | 1995 |
| Quainton Shop Limited | Wholesale & retail | 2023 |
| Quainton Station Road Limited | Households | 2023 |
| Quality & Compassion Ltd | Health & social care | 2013 |
| Quality Anchor Ltd | Health & social care | 2026 |
| Quality Chops Ltd | Extraterritorial | 2024 |
| Quality Milk Producers Limited | Manufacturing | 2018 |
| Quanta Academy LLP | | 2025 |
| Quantix Systems Ltd | Information & communication | 2025 |
| Quantum Data Labs Limited | Information & communication | 2025 |
| Quantumcraft Solutions Limited | Professional & scientific | 2025 |
| Quarrysoft Limited | Information & communication | 2010 |
| Queen of the Kitchen Ltd | Hospitality | 2018 |
| Queensmead Auto Services Limited | Transport & logistics | 1994 |
| Quenxo Limited | Professional & scientific | 2025 |
| Quercus Alternative Provision Ltd | Education | 2026 |
| Quercus Civil Engineering Ltd | Construction | 2023 |
| Quercus Construction Management Ltd | Construction | 2007 |
| Quest Equipment Limited | Wholesale & retail | 2003 |
| Quickoo Private Limited | Transport & logistics | 2025 |
| Quickseal (UK) Limited | Manufacturing | 1995 |
| Quik Repair Ltd | Wholesale & retail | 2021 |
| Quik Solutions Ltd | Information & communication | 2022 |
| Quikr Data Ltd | Information & communication | 2016 |
| Quinspec Consultants Limited | Manufacturing | 2015 |
| Quintessential Analysis Limited | Information & communication | 2016 |
| Quipdata Limited | Administrative & support | 2000 |
| Quotidian Project Management Services (PMS) Limited | Professional & scientific | 2016 |
| QW Capital Ltd | Financial services | 2026 |
| QW Research LLP | | 2024 |
| QZ Oriental Restaurant Limited | Hospitality | 2024 |
| R & a Engineering Limited | Manufacturing | 2005 |
| R & C Mole Investments Limited | Financial services | 2022 |
| R & R Displays Limited | Construction | 2003 |
| R & S Development (AY) Ltd | Construction | 2025 |
| R & S Family Holdings Limited | Real estate | 2025 |
| R & S Properties (Bucks) Ltd | Real estate | 2020 |
| R & S Travel Services Limited | Transport & logistics | 2011 |
| R & T Turner Limited | Real estate | 2016 |
| R a W Construction Services Limited | Construction | 2017 |
| R B Shelving Installations Ltd | Construction | 2018 |
| R D Education Limited | Education | 2011 |
| R D Hilliard Limited | Professional & scientific | 2013 |
| R E Wright Engineering Services Ltd | Professional & scientific | 2012 |
| R F Brickwork Limited | Construction | 2013 |
| R F Vass Construction Limited | Construction | 2018 |
| R G Grab Hire Ltd | Water & waste | 2017 |
| R J Capel Limited | Professional & scientific | 2025 |
| R Jackson Marine Services Ltd | Manufacturing | 2013 |
| R S Fire Protection UK Ltd | Professional & scientific | 2000 |
| R S Mann Accountancy Services Limited | Professional & scientific | 2017 |
| R Seller Ltd | Wholesale & retail | 2023 |
| R Wilson Builders Limited | Construction | 2026 |
| R&B Dynamic Ltd | Wholesale & retail | 2012 |
| R&J 14 Ltd | Transport & logistics | 2025 |
| R&L Project Services LLP | | 2016 |
| R&P Installations Ltd | Manufacturing | 2018 |
| R&P Logistics Ltd | Transport & logistics | 2026 |
| R&R Building and Maintenance Services Ltd | Construction | 2022 |
| R&S Global Ventures Ltd | Wholesale & retail | 2025 |
| R-Group Oxford Ltd | Wholesale & retail | 2016 |
| R. Shah (Aylesbury) Limited | Wholesale & retail | 2000 |
| R.A. Bell Ltd | Professional & scientific | 2016 |
| R.A.C.E. Energy Limited | Administrative & support | 2003 |
| R.A.W Carpentry and Construction Ltd | Construction | 2022 |
| R.F.S. (UK) Limited | Wholesale & retail | 1990 |
| R.O.D. Draintech Limited | Construction | 1997 |
| RA Chicken and Burgers Limited | Hospitality | 2025 |
| Raaya Properties Ltd | Real estate | 2025 |
| Rabbit Retail Limited | Wholesale & retail | 2020 |
| Raca Solutions Limited | Information & communication | 2011 |
| Race Aero Ltd | Manufacturing | 2022 |
| Race Line IT Ltd | Information & communication | 2023 |
| Racedown Alps Limited | Agriculture & fishing | 1973 |
| Rach Training Ltd | Education | 2022 |
| Rachel Claridge Ltd | Professional & scientific | 2013 |
| Rachel Fletcher Associates Ltd | Professional & scientific | 2010 |
| Raczka Windows Ltd | Construction | 2024 |
| Radcliffe Hearing Ltd | Health & social care | 2024 |
| Radford Court Management Co Limited | Real estate | 2008 |
| Radha Enterprises Ltd | Information & communication | 2019 |
| Radiant Pearl Emporium Limited | Wholesale & retail | 2018 |
| Radio London Ltd | Information & communication | 2001 |
| Radley Aylesbury Limited | Construction | 2004 |