| Fit for ALL New Co Limited | Arts & recreation | 2008 |
| Fit LAB (Brighton & Hove) Limited | Arts & recreation | 1993 |
| Fit State Training Limited | Arts & recreation | 2011 |
| Fitfemme Shop Ltd | Wholesale & retail | 2025 |
| Fitness Content Agency Ltd | Information & communication | 2024 |
| Fitness Garage Limited | Wholesale & retail | 2013 |
| Fitnessisc.A.Lling Ltd | Arts & recreation | 2026 |
| Five Construction Limited | Construction | 2023 |
| Five Focus Ltd | Other services | 2012 |
| Five Norfolk Square Management Company Limited | Households | 1989 |
| Five Oaks Solar Farm Limited | Energy | 2014 |
| FIX and Clean Limited | Administrative & support | 2024 |
| FIX Professional Ltd | Construction | 2025 |
| FIX Tech Experts Limited | Information & communication | 2024 |
| Flame Sauna Limited | Hospitality | 2026 |
| Flaming Bear Limited | Extraterritorial | 2017 |
| Flanagan Ltd | Professional & scientific | 2021 |
| Flannel Communications Limited | Information & communication | 2006 |
| Flare Arts CIC | Arts & recreation | 2022 |
| Flat Seven Limited | Households | 1995 |
| Flavour (Unit SU 65) Limited | Hospitality | 2013 |
| Flawless Facades Ltd | Construction | 2020 |
| Fleming Financial Holdings Limited | Financial services | 2024 |
| Fleming Financial Limited | Financial services | 2002 |
| Fleur Dental Limited | Health & social care | 2021 |
| Flexitreks Ltd | Administrative & support | 2012 |
| Flexotronix Limited | Information & communication | 2018 |
| Flexx Digital Ltd | Information & communication | 2006 |
| Flexx Holdings Limited | Financial services | 2019 |
| Flexx Property Ltd | Real estate | 2020 |
| Flexx Saas Ltd | Information & communication | 2025 |
| Flexxable Ltd | Information & communication | 2017 |
| FLN Consulting Limited | Health & social care | 2024 |
| Flock Fitness Limited | Arts & recreation | 2017 |
| Floooo | Information & communication | 2024 |
| Floor Sanding Partners Limited | Construction | 2016 |
| Floor-Man Sussex Ltd | Construction | 2026 |
| Flore Trading Limited | Wholesale & retail | 2025 |
| Floriana Rotunda Limited | Hospitality | 2008 |
| Flowers in Cornwall Ltd | Administrative & support | 2025 |
| Flush Force UK Limited | Water & waste | 2025 |
| Flux Books Limited | Wholesale & retail | 2025 |
| Fluxions Limited | Professional & scientific | 2024 |
| FLY High COM Investments Ltd | Real estate | 2019 |
| FLY High Investments Ltd | Real estate | 2019 |
| FLY Like Dragon Ltd | Information & communication | 2024 |
| Flying Wing Holdings Limited | Real estate | 2021 |
| Flynt Studio Ltd | Information & communication | 2024 |
| Flywheel Learning Limited | Professional & scientific | 2017 |
| Flywheel Real Estate Limited | Real estate | 2015 |
| FMF Podiatry Ltd | Health & social care | 2025 |
| FNR Dent Limited | Health & social care | 2019 |
| FO Botanica Limited | Wholesale & retail | 2023 |
| Focused Events Limited | Arts & recreation | 1999 |
| Fohlmann Limited | Health & social care | 2014 |
| Folde and Sonder Ltd | Other services | 2024 |
| Folklore Sessions Ltd | Arts & recreation | 2021 |
| Folklore Venues Ltd | Arts & recreation | 2025 |
| Fonthill Road Hove RTM Company Limited | Extraterritorial | 2025 |
| Food Network for Ethical Trade | Other services | 2019 |
| Foodhaven Ltd. | Professional & scientific | 2012 |
| Foodielicious Kitchen Ltd | Hospitality | 2024 |
| Foodini Club Ltd | Hospitality | 2016 |
| Forcemapping Ltd | Information & communication | 2005 |
| Ford G2 Solar Farm Limited | Energy | 2014 |
| Forecast Developments Limited | Real estate | 2013 |
| Foredown Accountancy Ltd | Professional & scientific | 2021 |
| Foreman Investments Limited | Real estate | 1973 |
| Foremost Integrated Circuits Limited | Professional & scientific | 2011 |
| Forestcrave Limited | Information & communication | 1994 |
| Form In-Sight Trading Ltd | Arts & recreation | 2023 |
| Form Pilates Shoreham Ltd | Arts & recreation | 2025 |
| Form Sussex Ltd | Construction | 2025 |
| Formula Academy Junior Limited | Education | 2018 |
| Forte's Quality Foods (Sussex) Limited | Real estate | 1949 |
| Fortes(Brighton & Hove)Limited | Real estate | 1946 |
| Forty Years on Limited | Real estate | 2016 |
| Forty-Eight Ventnor Villas (Hove) Limited | Households | 1961 |
| Forward Industries UK Limited | Manufacturing | 2018 |
| Foundana Ltd | Wholesale & retail | 2022 |
| Foundation 5 Ltd | Professional & scientific | 2017 |
| Foundation Figures Ltd | Construction | 2022 |
| Founders Caddie Ltd | Information & communication | 2019 |
| Foundry House ELM Grove Limited | Households | 2024 |
| Four Beacon Limited | Professional & scientific | 2025 |
| Four Cissbury Road Ltd | Households | 1999 |
| Four Door Productions Ltd | Other services | 2017 |
| Four Moods Coffee Limited | Wholesale & retail | 2026 |
| Four Screws Limited | Other services | 2025 |
| Four Seasons International Ltd | Wholesale & retail | 2020 |
| Fourrise Estates Ltd | Real estate | 2025 |
| Fourth AVE Sussex Ltd | Construction | 2025 |
| FOX in a Box Solutions Limited | Information & communication | 2007 |
| Foxan Ltd | Construction | 2019 |
| Foxden Enterprises Limited | Financial services | 2026 |
| Fractional Growth Ltd | Professional & scientific | 2026 |
| Fractional IR Ltd | Professional & scientific | 2024 |
| Fralto Ltd | Professional & scientific | 2013 |
| Frame of Mind Ltd | Other services | 2010 |
| Framework Property Maintenance Ltd | Arts & recreation | 2025 |