| Firs House Limited | Hospitality | 2018 |
| Firs Retail Limited | Wholesale & retail | 2019 |
| First 4 Locksmiths Ltd | Administrative & support | 2013 |
| First 9 Group Ltd | Construction | 2025 |
| First Cafes Limited | Hospitality | 1978 |
| First Call Loos Limited | Construction | 2019 |
| First Call Motor Care Ltd | Wholesale & retail | 2025 |
| First Call Travel (Bridgend) Limited | Transport & logistics | 2011 |
| First Call Travel Limited | Transport & logistics | 2009 |
| First Chain LAB Limited | Information & communication | 2021 |
| First Choice Auto Spares Ltd | Wholesale & retail | 2019 |
| First Choice Energy Ltd | Construction | 2020 |
| First Choice Group Limited | Information & communication | 2015 |
| First Choice Tech Limited | Information & communication | 2025 |
| First Class Estates Limited | Real estate | 2018 |
| First Class Label Ltd | Other services | 2020 |
| First Class Recovery Limited | Transport & logistics | 2025 |
| First Class Roofing Solutions Ltd | Construction | 2024 |
| First Construction Safety Ltd | Professional & scientific | 2018 |
| First Contact Production Ltd | Administrative & support | 2018 |
| First Corporate Group UK Ltd | Wholesale & retail | 2019 |
| First Digital Holdings Limited | Information & communication | 2016 |
| First Digital Systems Ltd | Information & communication | 2018 |
| First Distribution Ltd | Transport & logistics | 2019 |
| First Energy Business Supply Ltd | Wholesale & retail | 2026 |
| First Energy Collections Ltd | Wholesale & retail | 2026 |
| First Energy Trading Ltd | Professional & scientific | 2026 |
| First Fiddle Ltd | Professional & scientific | 2024 |
| First for Property Management Ltd | Real estate | 2013 |
| First Forte Limited | Other services | 2012 |
| First Grand Cleaning Services Limited | Administrative & support | 2025 |
| First Home Tenerife Ltd | Administrative & support | 2024 |
| First in Mortgages Ltd | Financial services | 2016 |
| First Infrastructure Group Limited | Professional & scientific | 2011 |
| First Kitchens Ltd | Wholesale & retail | 2016 |
| First Layer Ltd | Wholesale & retail | 2018 |
| First Light Cloud Ltd | Information & communication | 2025 |
| First Line Family Law Limited | Professional & scientific | 2024 |
| First Line Motors Limited | Wholesale & retail | 2011 |
| First Look Designs Limited | Information & communication | 2005 |
| First Mahi Investment Holding & Trading Limited | Professional & scientific | 2017 |
| First Mile Education Limited | Education | 2025 |
| First Modular Limited | Construction | 1991 |
| First Name Trading Ltd | Wholesale & retail | 2026 |
| First on Imaging and Diagnostics Ltd | Health & social care | 2026 |
| First Path Trading Limited | Wholesale & retail | 2025 |
| First Payment Supply Ltd | Professional & scientific | 2026 |
| First Plumb Ltd | Construction | 2019 |
| First Point Itec Ltd | Wholesale & retail | 2021 |
| First Point Lighting Ltd | Manufacturing | 2014 |
| First Point Solutions Limited | Administrative & support | 2019 |
| First Rate Fire Protection Ltd | Other services | 2024 |
| First Safe Travel Ltd | Transport & logistics | 2025 |
| First Sahara Company Ltd | Wholesale & retail | 2025 |
| First Serve Ventures Ltd | Financial services | 2025 |
| First Steps Penarth Limited | Health & social care | 2020 |
| First Stop Landscapes Ltd | Administrative & support | 2020 |
| First Thread Software Ltd | Information & communication | 2025 |
| First Time (UK) Group Ltd | Administrative & support | 2018 |
| First Velocity, Ltd | Information & communication | 2019 |
| First W Motors Limited | Wholesale & retail | 2019 |
| FIRST4LEISURE.COM Limited | Wholesale & retail | 2006 |
| Firstbrite Co., Ltd | Extraterritorial | 2016 |
| Firstcall - WE ADD Value Limited | Administrative & support | 2017 |
| Firsthand Construction Ltd | Construction | 2017 |
| Firstlevel Services Ltd | Administrative & support | 2021 |
| FIRSTPROPERTY99 Ltd | Real estate | 2021 |
| Fiscal Fit Accountants Ltd | Administrative & support | 2021 |
| Fish & Field Limited | Hospitality | 2004 |
| Fish and Chips Caroline Street Ltd | Hospitality | 2025 |
| Fish at AFB Ltd | Hospitality | 2025 |
| Fish City Ltd | Wholesale & retail | 2024 |
| Fish Reaper Ltd | Wholesale & retail | 2022 |
| Fisher Bell Business Services Limited | Professional & scientific | 2012 |
| Fisher Isle PC | | 2017 |
| Fisherfilm Limited | Information & communication | 2017 |
| Fisheries Cardiff Limited | Hospitality | 2021 |
| FISHERIES127 Ltd | Hospitality | 2026 |
| Fishermans Cottage Robin Hoods Bay Ltd | Hospitality | 2022 |
| Fishers Convenience Stores Limited | Wholesale & retail | 2021 |
| Fishing Supercup Limited | Administrative & support | 2017 |
| Fisker (GB) Limited | Manufacturing | 2018 |
| Fit & FIX Cardiff Ltd | Construction | 2025 |
| Fit for Purpose Products Limited | Other services | 2016 |
| Fit Univers Ltd | Wholesale & retail | 2025 |
| Fit&Hit Ltd | Wholesale & retail | 2025 |
| FIT2TRAIN Ltd | Education | 2014 |
| Fitailor International Co., Ltd. | Extraterritorial | 2007 |
| Fitaura Ltd | Wholesale & retail | 2024 |
| Fitcy Health Limited | Other services | 2020 |
| Fitfab Limited | Wholesale & retail | 2019 |
| Fitfam Personal Training Ltd | Other services | 2023 |
| Fitgle Ltd | Other services | 2025 |
| Fitist Ltd | Health & social care | 2018 |
| Fitkitpro International Ltd | Arts & recreation | 2018 |
| Fitknee Ltd | Other services | 2025 |
| Fitmynd Nutrition Ltd | Wholesale & retail | 2026 |
| Fitness Academy W Ltd | Education | 2023 |
| Fitness Quarter (Cardiff) Limited | Arts & recreation | 2026 |
| Fitness Quarter LLP | | 2024 |