| Fintech IT Consultancy Ltd | Information & communication | 2018 |
| Finxdigital Limited | Information & communication | 2025 |
| Fiola & Associates Ltd | Professional & scientific | 2021 |
| Firbank Court (Leighton Buzzard) Management Limited | Households | 1991 |
| Fircott Consulting Limited | Professional & scientific | 2014 |
| Fire & Electrical Safety Limited | Construction | 2010 |
| Fire & Security Solutions Limited | Construction | 2007 |
| Fire Aware Ltd | Other services | 2024 |
| Fire AXE Limited | Public administration | 2021 |
| Fire Prevention Specialists Ltd | Construction | 2019 |
| Fireaway Germany Ltd | Hospitality | 2025 |
| Fireaway Pizza Ltd | Wholesale & retail | 2015 |
| Fireaway SW4 Ltd | Other services | 2024 |
| Firebase Media Limited | Professional & scientific | 2026 |
| Firebrand Promotions Limited | Wholesale & retail | 2002 |
| Fireflyvirtualsolutions Ltd | Administrative & support | 2026 |
| Fireox Limited | Wholesale & retail | 2022 |
| Firesound Music Limited | Information & communication | 2023 |
| Firestop Technologies Ltd | Public administration | 2025 |
| Firetech Installation Ltd | Construction | 2023 |
| Firewire Trading Limited | Wholesale & retail | 2021 |
| Firewood Fuel MK Ltd | Agriculture & fishing | 2020 |
| Firm Five Limited | Information & communication | 2023 |
| Firmly Rooted Ltd | Education | 2021 |
| First & Clean Paint Limited | Construction | 2025 |
| First Avenue Holdings Limited | Financial services | 2023 |
| First Avenue Supplies Limited | Wholesale & retail | 2003 |
| First Base Ground Screws UK Ltd | Construction | 2020 |
| First Caas Ltd | Information & communication | 2021 |
| First Centric Care Ltd | Administrative & support | 2022 |
| First Choice Benefits Ltd | Professional & scientific | 2023 |
| First Choice Fire and Security Services Ltd | Administrative & support | 2024 |
| First Choice Physiotherapy Ltd | Health & social care | 2025 |
| First Class Athletics Ltd | Professional & scientific | 2022 |
| First Class Autos Limited | Wholesale & retail | 2022 |
| First Class Supplies UK Limited | Other services | 2022 |
| First Class Unique Care Ltd | Health & social care | 2014 |
| First Degree Homes Limited | Real estate | 2001 |
| First Facilities Management Ltd | Administrative & support | 2016 |
| First Focus MK Limited | Hospitality | 2022 |
| First Haul Ltd | Transport & logistics | 2009 |
| First Health Trusts Limited | Professional & scientific | 1998 |
| First Light Children's Yoga Ltd | Arts & recreation | 2015 |
| First Line Sports Ltd | Wholesale & retail | 2008 |
| First Pamaj Limited | Health & social care | 2015 |
| FIRST4CABLING Limited | Information & communication | 2020 |
| Firstcall Logistics Ltd | Transport & logistics | 2024 |
| Firstland Developments Ltd | Construction | 2015 |
| Firstlight Products Limited | Wholesale & retail | 1980 |
| Fish ARE Best Ltd | Information & communication | 2012 |
| Fish Bazar MK Limited | Wholesale & retail | 2019 |
| Fish Technologies Limited | Information & communication | 2026 |
| Fisherman Creative Ltd | Information & communication | 2012 |
| Fishers Marshall Enterprise UK Limited | Financial services | 2021 |
| Fisk TM Ltd | Construction | 2024 |
| Fiske Decorators Limited | Construction | 2004 |
| Fit 4 Everything Ltd | Other services | 2017 |
| Fitlife Propco Limited | Arts & recreation | 2015 |
| Fitness Tribe MK Ltd | Arts & recreation | 2022 |
| Fitz & Starts Ltd | Administrative & support | 2017 |
| Fitz Housing Ltd | Real estate | 2016 |
| Fitzlan Limited | Real estate | 2018 |
| Fitzroy Healthcare Ltd | Health & social care | 2026 |
| Fitzwilliam Dunne Limited | Professional & scientific | 2022 |
| Five Akhis (Herts) Ltd | Hospitality | 2025 |
| Five Akhis Group Ltd | Hospitality | 2021 |
| Five Corporate Finance Limited | Professional & scientific | 2014 |
| Five Foods Limited | Hospitality | 2026 |
| Five Magpies Ltd | Real estate | 2011 |
| Five Mile Drive Holdings Limited | Energy | 2015 |
| Five Mile Drive Solar Park Limited | Energy | 2013 |
| Five Only Enterprises Ltd | Financial services | 2025 |
| Five River Contracting Ltd | Construction | 2025 |
| Five River Homes Limited | Real estate | 2020 |
| Five Star Car Wash Solution (UK) Ltd | Other services | 2004 |
| Five Star Fitness MC Ltd | Arts & recreation | 2015 |
| Five Star USA Nails Ltd | Other services | 2026 |
| Five Wheels Limited | Wholesale & retail | 2020 |
| FIVE12 Games Ltd | Information & communication | 2016 |
| Fivestar Performance Ltd | Wholesale & retail | 2023 |
| FIX Fast Property Maintenance Ltd | Manufacturing | 2025 |
| FIX IT Flooring, Plumbing & Heating Ltd | Construction | 2016 |
| Fix-Asap Limited | Hospitality | 2023 |
| Fixingup Ltd | Construction | 2024 |
| Fixter Limited | Other services | 2016 |
| Fizaans Enterprise Ltd | Wholesale & retail | 2022 |
| Fizzpopbang Limited | Professional & scientific | 2012 |
| Fizzy Milk Limited | Information & communication | 2024 |
| Fjord Engineering Ltd | Professional & scientific | 2016 |
| Fjord Logic Ltd | Wholesale & retail | 2025 |
| FK2 Networks Limited | Information & communication | 2018 |
| FK2 Productions Limited | Wholesale & retail | 2021 |
| FKM45 Limited | Administrative & support | 2018 |
| FL Global Trading Ltd | Wholesale & retail | 2017 |
| FL1 Digital Ltd | Information & communication | 2023 |
| Flack Property Consultants Ltd | Professional & scientific | 2022 |
| Flag Locum Services Limited | Extraterritorial | 2004 |
| Flakie Trading Ltd | Wholesale & retail | 2024 |
| Flamingo Consultants PVT Limited | Information & communication | 2010 |
| Flamingo Records Limited | Information & communication | 2018 |