| Fire Installation Services Limited | Arts & recreation | 1994 |
| Fire Logic Ltd | Public administration | 2022 |
| Fire ME UP Ltd | Hospitality | 2024 |
| Fire Nemesis Ltd | Administrative & support | 2025 |
| Fire Safety Risk Management Solutions Ltd | Public administration | 2018 |
| Fire Solutions Construction Ltd | Construction | 2025 |
| Fire Structure Limited | Public administration | 2015 |
| Firebird Precision Strip Limited | Manufacturing | 2011 |
| Firecore Systems Ltd | Construction | 2026 |
| Firecrest Assets Limited | Financial services | 2024 |
| Fired Arts S11 Limited | Wholesale & retail | 2024 |
| Fired UP and Painting Ltd | Wholesale & retail | 2026 |
| Fireface Music Production Limited | Information & communication | 2013 |
| Firefly Dynamics Ltd | Professional & scientific | 2022 |
| Firefly Laser Limited | Manufacturing | 2010 |
| Firegable Limited | Professional & scientific | 1976 |
| Firephonic Audio Limited | Information & communication | 2026 |
| Firesafe Services (North East) Limited | Public administration | 2009 |
| Firesafetycomplete Limited | Professional & scientific | 2012 |
| Firma-Chrome Limited | Manufacturing | 1987 |
| Firmus Home Solutions Ltd | Construction | 2021 |
| First 4 Supplies Limited | Construction | 2001 |
| First Accountancy Associates Ltd | Professional & scientific | 2023 |
| First Blossom Limited | Wholesale & retail | 2025 |
| First Business Services Ltd | Information & communication | 2008 |
| First Call Gate Automation Ltd | Manufacturing | 2020 |
| First Choice Air Conditioning Limited | Energy | 2017 |
| First Choice MOT and Service Centre Limited | Wholesale & retail | 2018 |
| First Connect Utility Solutions Ltd | Professional & scientific | 2016 |
| First Courier Ltd | Other services | 2019 |
| First Degree (Devonshire Works) Ltd | Real estate | 2019 |
| First Degree Investment Management Ltd | Real estate | 2011 |
| First Degree Living Ltd | Real estate | 2011 |
| First FIX Supplies Limited | Wholesale & retail | 2007 |
| First FIX UK Limited | Construction | 2002 |
| First Football Shirts Ltd | Wholesale & retail | 2021 |
| First GAS & Plumbing Ltd | Construction | 2026 |
| First Impressions Studio Ltd | Information & communication | 2025 |
| First Kebabish Limited | Wholesale & retail | 2015 |
| First Line Pods Limited | Wholesale & retail | 2019 |
| First Media Partners Limited | Professional & scientific | 2020 |
| First National Housing Trust Limited | Real estate | 1933 |
| First Property Consulting Limited | Real estate | 2002 |
| First Shot Media Ltd | Information & communication | 2021 |
| First Sight Holdings Limited | Professional & scientific | 2016 |
| First South Yorkshire Limited | Transport & logistics | 1989 |
| First Steps Nursery School (Dore) Limited | Education | 2011 |
| First Sunshine Management Ltd | Hospitality | 2024 |
| First Support Care Ltd | Education | 2021 |
| First Thai Supermarket Ltd | Wholesale & retail | 2024 |
| First Trust Finance Limited | Administrative & support | 2007 |
| First Vision Eyecare Limited | Health & social care | 2023 |
| First Wave Ltd | Hospitality | 2022 |
| Firsteel Roberts Limited | Professional & scientific | 1957 |
| Firsteel Steel Processing Limited | Professional & scientific | 1893 |
| Firstlink Auto Parts Ltd | Wholesale & retail | 2012 |
| Firth Campers Limited | Manufacturing | 2015 |
| Firth Diesel Injection Limited | Wholesale & retail | 2002 |
| Firth Estates Ltd | Real estate | 2020 |
| Firth Investment Group Ltd | Financial services | 2023 |
| Firth NDT Limited | Manufacturing | 2019 |
| Firth Park Boxing Academy CIC | Arts & recreation | 2026 |
| Firth Park Car Clinic Limited | Wholesale & retail | 2017 |
| Firth Park Fish and Chicks Ltd | Hospitality | 2026 |
| Firth Park Property Limited | Real estate | 2022 |
| Firth Park Shawarma and Bakery Ltd | Hospitality | 2026 |
| Firths Window Cleaning Services Limited | Administrative & support | 2013 |
| Firthvale Ltd | Construction | 2015 |
| Firvale Community Hub | Information & communication | 2013 |
| FIS Projects Ltd | Professional & scientific | 2021 |
| Fisa Properties Ltd | Real estate | 2025 |
| Fish & Chip Van Events Ltd | Hospitality | 2022 |
| Fish and Chicks Limited | Hospitality | 2025 |
| Fish and Father Limited | Manufacturing | 2018 |
| Fish Feet Limited | Other services | 2010 |
| Fish Properties Limited | Real estate | 2024 |
| Fisher Patton and the Red Baron Limited | Wholesale & retail | 2018 |
| Fisherbell Limited | Health & social care | 1996 |
| Fishers Electrical Services NE Limited | Construction | 2017 |
| Fishponds View Management Company Limited | Households | 2023 |
| Fist Motors Ltd | Wholesale & retail | 2019 |
| Fit From Here Limited | Health & social care | 2025 |
| Fit-Af Limited | Arts & recreation | 2026 |
| FIT4-PHYSIO Limited | Health & social care | 2014 |
| FIT4FUNCTION Performance Ltd | Health & social care | 2025 |
| FIT4IT Fitness Ltd | Arts & recreation | 2012 |
| FIT4RETAIL Ltd | Wholesale & retail | 2016 |
| Fitcheck Clinic Ltd | Health & social care | 2025 |
| Fitfoodielarisa Limited | Information & communication | 2026 |
| Fitness Business Launch Ltd | Education | 2024 |
| Fitness Frase Limited | Other services | 2022 |
| Fitness Fusion Training Ltd | Other services | 2024 |
| Fitness Improvement Therapy Ltd | Health & social care | 2011 |
| Fitness South Yorkshire Ltd | Arts & recreation | 2025 |
| Fitness@Dal's Ltd | Health & social care | 2017 |
| Fitphysique Network Ltd | Arts & recreation | 2020 |
| Fitted Windows Limited | Construction | 2025 |
| Fitter Than Average Ltd | Information & communication | 2020 |
| Fitu Fitness Limited | Arts & recreation | 2022 |
| Fitz Retail Limited | Professional & scientific | 2017 |