| Foster Gray Properties Ltd | Real estate | 2019 |
| Four Pharmaceuticals Limited | Manufacturing | 1997 |
| Fourstones Limited | Professional & scientific | 2016 |
| FOX Huhu Trading Limited | Construction | 2026 |
| Frances Manning Education Leadership Support Ltd | Education | 2022 |
| Franchesqua Sings Ltd | Information & communication | 2023 |
| Free Flow Environmental Ltd | Water & waste | 2018 |
| Free Range Creative Studio Ltd | Arts & recreation | 2022 |
| Friendly GP Services Ltd | Health & social care | 2026 |
| Full FAT Electronics Ltd | Extraterritorial | 2020 |
| G & a Plumbing and Heating Engineers Limited | Construction | 2000 |
| G & B Project Solutions Limited | Construction | 2025 |
| G & D Auto Services Limited | Wholesale & retail | 2006 |
| G&G Fenestration Ltd | Construction | 2021 |
| G.I. Installation Services Limited | Construction | 2026 |
| G.Osborn Decorator's Ltd | Construction | 2008 |
| Gaskin Development Herts Ltd | Information & communication | 2009 |
| Gaskin Property Ltd | Real estate | 2022 |
| Gastrointestinal Health Ltd | Health & social care | 2025 |
| Ginn Electrical Ltd | Construction | 2018 |
| Glass and Quartz Ltd | Extraterritorial | 2023 |
| Gloucester Court Limited | Real estate | 2003 |
| Gnbros Ltd | Real estate | 2024 |
| GNP Consultancy Ltd | Professional & scientific | 2016 |
| Go Pharmaconsulting Ltd | Professional & scientific | 2025 |
| Going Somewhere Ltd | Extraterritorial | 2024 |
| Gomin Ltd | Information & communication | 2026 |
| GOOD4EARTH Ltd | Professional & scientific | 2025 |
| Goodmans Motor Homes Limited | Wholesale & retail | 2007 |
| Goodmayes 38 Limited | Real estate | 2008 |
| Goshawk Technology Ltd | Information & communication | 2012 |
| Gracesimba Ltd | Information & communication | 2021 |
| Greece by Design Limited | Administrative & support | 1994 |
| Green Genie Spirits Limited | Wholesale & retail | 2022 |
| Greencroft Limited | Extraterritorial | 2020 |
| Greengairs Advisory Limited | Professional & scientific | 2010 |
| Greens Supplies Limited | Wholesale & retail | 2023 |
| Grey Matter Fire & Security Limited | Administrative & support | 2005 |
| Gridlocked Ltd | Construction | 2008 |
| Groove DJ School Ltd | Education | 2025 |
| Grove Management Company (Welwyn) Limited | Households | 2002 |
| Growth Pilot AI Limited | Information & communication | 2026 |
| GSD Global Ltd. | Administrative & support | 2007 |
| H H Instyle Limited | Administrative & support | 2017 |
| Haast Limited | Construction | 2019 |
| Hampton Business Court Limited | Real estate | 1987 |
| Hanyaz Ltd | Arts & recreation | 2025 |
| Hargem Properties Ltd | Real estate | 2011 |
| Harmonix Productions Ltd | Professional & scientific | 2023 |
| Harvest Court Residents Association Limited | Administrative & support | 1985 |
| Hastings and Havill Limited | Hospitality | 2015 |
| Hategan Transport Ltd | Transport & logistics | 2025 |
| Haus Eleven Group Ltd | Information & communication | 2026 |
| Hawkwood Consulting Limited | Professional & scientific | 2024 |
| Hayes Precision Gauges Ltd | Manufacturing | 2025 |
| Head Mistress Limited | Other services | 2008 |
| Heal for Black People CIC | Education | 2024 |
| Health Revival Expert Ltd | Extraterritorial | 2025 |
| Health Revival Group Ltd | Health & social care | 2025 |
| Help & Safety Equipment Ltd | Wholesale & retail | 2008 |
| Henry Hound Limited | Other services | 2005 |
| Hensal Communications Ltd | Professional & scientific | 2021 |
| Hertford House by Tewinbury Limited | Hospitality | 2025 |
| Hertfordshire Architects Ltd | Professional & scientific | 2011 |
| Hertfordshire Gold Limited | Professional & scientific | 2024 |
| Hertfordshire Premier Plumbing and Heating Ltd | Construction | 2018 |
| Hertfordshire School of Jewellery Ltd | Arts & recreation | 2014 |
| Hertfordshire Slings CIC | Other services | 2025 |
| Herts & Beds Specialist Coaching Ltd | Education | 2020 |
| Herts Autos Ltd | Wholesale & retail | 2020 |
| Herts County Builders Limited | Construction | 2012 |
| Herts EV Specialists Ltd | Construction | 2020 |
| Herts Gravel and Brickworks Limited | Extraterritorial | 2020 |
| Herts MG Ltd | Wholesale & retail | 2019 |
| Herts Sports Academy Ltd | Education | 2024 |
| Hewitt Green Limited | Water & waste | 2019 |
| High Welwyn Limited | Extraterritorial | 2019 |
| Higham Ferrers Veterinary Clinic Ltd | Professional & scientific | 2013 |
| Hill Consultants Limited | Professional & scientific | 1996 |
| Hogies Online Limited | Administrative & support | 2010 |
| Home County Garden Rooms Limited | Construction | 2023 |
| Home-School Tutoring Hertfordshire & Cambridgeshire Limited | Education | 2024 |
| Homelocal Property Management Limited | Real estate | 1993 |
| House of Detention Limited | Real estate | 2002 |
| Huenique Ltd | Construction | 2024 |
| Huge Inns Limited | Hospitality | 2017 |
| Huntersmoon Workshop Ltd | Manufacturing | 2015 |
| Hwca Services Limited | Financial services | 2019 |
| Hwells Ltd | Wholesale & retail | 2022 |
| Hybrid Group Holdings Limited | Financial services | 2025 |
| Hybrid World Group Limited | Financial services | 2025 |
| Hybrid World Series Limited | Arts & recreation | 2025 |
| HYBRIDV10 Operations Limited | Information & communication | 2025 |
| HYBRIDV8 Operations Limited | Information & communication | 2025 |
| IAN Kitson Limited | Administrative & support | 2017 |
| Ignition Works Limited | Information & communication | 2015 |
| Iihg Limited | Real estate | 2024 |
| Illuminating Solutions Ltd | Manufacturing | 2019 |
| Illumni Collective Limited | Wholesale & retail | 2020 |
| Imatek Systems Limited | Manufacturing | 2015 |