| Fluxero Ltd | Professional & scientific | 2025 |
| Fluxus Auri Ltd | Manufacturing | 2018 |
| Flyresearch Limited | Professional & scientific | 2000 |
| FMH Consultancy Limited | Administrative & support | 2003 |
| FMR Trade Limited | Wholesale & retail | 2025 |
| Foal Park Limited | Professional & scientific | 2000 |
| Focus Radiodiagnostics Limited | Health & social care | 2010 |
| Focus RD Properties Limited | Real estate | 2017 |
| Foley Deliveries Ltd | Transport & logistics | 2026 |
| Foodie Wines Limited | Extraterritorial | 2021 |
| Footybits Limited | Wholesale & retail | 2005 |
| Forbes Ross & Company Limited | Professional & scientific | 1991 |
| Forbesinvest Limited | Real estate | 2023 |
| FORCE3 Metalworks Ltd | Manufacturing | 2023 |
| Fordham Interiors Limited | Construction | 2019 |
| Fordson Ltd | Extraterritorial | 2024 |
| Forecourt Assist North East Limited | Professional & scientific | 2014 |
| Foreign Anglican Church and Educational Association Limited | Other services | 1883 |
| Forensic Psychology Expert Ltd | Health & social care | 2021 |
| Forest Carbon Limited | Agriculture & fishing | 2007 |
| Forest Carbon Trustees Limited | Professional & scientific | 2023 |
| Forge Farm Management Limited | Real estate | 2018 |
| Fork Catering Ltd | Hospitality | 2024 |
| Forma-Care (UK) Ltd | Manufacturing | 2019 |
| Formedecon Ltd. | Professional & scientific | 1994 |
| Formula Coaching Ltd | Health & social care | 2024 |
| Formula Research Limited | Professional & scientific | 2025 |
| Formula Sidecar Racing Association (UK) Limited | Arts & recreation | 1997 |
| Forrest Park (Newton Aycliffe) Limited | Real estate | 2016 |
| Fortay Developments Limited | Construction | 2025 |
| Fortify Holdings Limited | Financial services | 2023 |
| Fortify Solutions (N.E.) Ltd | Construction | 2014 |
| Fortisventus Ltd | Wholesale & retail | 2025 |
| Fortune Palace Ltd | Hospitality | 2023 |
| Forward Sound Limited | Mining & quarrying | 2008 |
| Foss Court Management Company Limited | Households | 1997 |
| Foster Clark Engineering Limited | Manufacturing | 1999 |
| Fotoquirk Ltd | Information & communication | 2009 |
| Foulger Consulting Ltd | Professional & scientific | 2007 |
| Foundation Year Network Ltd | Information & communication | 2022 |
| Foundora Ltd | Wholesale & retail | 2025 |
| Fountain Land Limited | Real estate | 2020 |
| Four Reasons Ltd | Professional & scientific | 2026 |
| Fowler Enterprises International, Ltd | Information & communication | 2015 |
| Fowler Hatfield Portfolio Consulting Ltd | Professional & scientific | 2026 |
| Fowler Wynd Developments Limited | Real estate | 2018 |
| Fowlers Durham Ltd | Hospitality | 2024 |
| Foxcover Limited | Construction | 1998 |
| Foxley Wood Investments 2 Limited | Financial services | 2025 |
| FR Groundworks Limited | Construction | 2025 |
| FR Holdings Limited | Financial services | 2026 |
| FR Land & Property Ltd | Real estate | 2019 |
| FR Properties NE Limited | Real estate | 2026 |
| FR Surfacing Limited | Construction | 2021 |
| Fram Beauty Ltd | Other services | 2025 |
| Fram Ferment Ltd | Wholesale & retail | 2019 |
| Fram Pizza Ltd | Hospitality | 2019 |
| Frampton & Roebuck Limited | Real estate | 2014 |
| Framwellgate IT Limited | Public administration | 2017 |
| Fred & Louise Properties Ltd | Real estate | 2021 |
| Fred Henderson Limited | Wholesale & retail | 1999 |
| Fred Stoddart Limited | Construction | 1957 |
| Freddie Douglas & Co Ltd. | Administrative & support | 2020 |
| Frederick Dennison Limited | Real estate | 1937 |
| Freedom to BE UN Limited | Health & social care | 2026 |
| Frella Home Improvements Ltd | Professional & scientific | 2024 |
| French & Brown MOT Ltd | Wholesale & retail | 2026 |
| Fresh Cuts (NE) Ltd | Other services | 2025 |
| Freshstepper Group Ltd | Wholesale & retail | 2025 |
| Freshwater Bathrooms and Tiles Limited | Wholesale & retail | 2010 |
| Freya Lillie Ltd | Wholesale & retail | 2017 |
| Friends of Dcsf Ltd | Education | 1938 |
| Friends of Durham City Gymnastics Club Limited | Education | 2017 |
| Front Street Garage Limited | Administrative & support | 2004 |
| Frostheart Ltd | Information & communication | 2026 |
| FT Management Consultants Limited | Financial services | 2008 |
| FU Ning Ltd | Wholesale & retail | 2024 |
| Fuel for Demigods Ltd | Wholesale & retail | 2024 |
| Fulchester Group (Homes) Limited | Households | 2026 |
| Fulforth Landscapes & Driveways Ltd | Administrative & support | 2025 |
| Full Circle Studios Ltd | Information & communication | 2025 |
| Full Steam Ahead FSA Ltd | Other services | 2023 |
| Fulleylove Limited | Wholesale & retail | 2025 |
| Fuls Limited | Financial services | 2014 |
| Fundamental ISP Ltd | Health & social care | 2025 |
| Funk Designs Limited | Wholesale & retail | 1997 |
| Furkan Celik Ltd | Wholesale & retail | 2025 |
| Future Fit (NE) Limited | Arts & recreation | 2015 |
| Future Generation Retail Ltd | Wholesale & retail | 2020 |
| Future Leisure in Coxhoe (Flic) | Arts & recreation | 2011 |
| Future Power Projects Ltd | Administrative & support | 2022 |
| FWS Consultants Limited | Professional & scientific | 2000 |
| FYC Limited | Health & social care | 2014 |
| G & L Groundworks Limited | Construction | 2020 |
| G & R Groundworks NE Limited | Construction | 2026 |
| G and R Dixon Ltd | Professional & scientific | 2018 |
| G Boyd Utilities Ltd | Construction | 2023 |
| G Hall Offshore Services Limited | Mining & quarrying | 2023 |
| G J Plant Hire Limited | Wholesale & retail | 2004 |
| G Linstead Properties Ltd | Real estate | 2022 |