| Habi Pharma Limited | Professional & scientific | 2024 |
| Habitat HQ Ltd | Real estate | 2025 |
| Hadham Group Limited | Construction | 2020 |
| Hadham Hall Management Company Limited | Households | 1993 |
| Hadham Timber Windows Limited | Construction | 2025 |
| Hadstone Energy Storage Developments Limited Liability Partnership | | 2024 |
| Hair by Millie-Mae Ltd | Other services | 2024 |
| Hairy Tails Ltd | Other services | 2021 |
| Halcyon Accountancy Limited | Professional & scientific | 2012 |
| Halcyon Minds Ltd | Health & social care | 2013 |
| Halcyon Residents Management Limited | Households | 1997 |
| Halcyon Retail Ltd | Wholesale & retail | 2010 |
| Halcyon X Ltd | Financial services | 2025 |
| Hale Physiotherapy and Exercise Limited | Health & social care | 2007 |
| Hall & Co Accountancy Ltd | Professional & scientific | 2017 |
| Hall Life Sciences Ltd | Information & communication | 2019 |
| Halo Social - Social Media Management Ltd | Professional & scientific | 2026 |
| Hamlet Pubs Limited | Hospitality | 2015 |
| Hammersmatch Builders Limited | Real estate | 1981 |
| Hammersmatch Developments Limited | Construction | 1983 |
| Hammersmatch Properties (Welwyn) Limited | Construction | 1986 |
| Hampton Medical Conferences Limited | Administrative & support | 1991 |
| Hampton Search Limited | Administrative & support | 2014 |
| Hanbury GRP Ltd | Information & communication | 2024 |
| Hannah Brace Conveyancing Ltd | Professional & scientific | 2026 |
| Hanovia Gold Animal Trust C.I.C. | Health & social care | 2021 |
| Hanwhit Limited | Professional & scientific | 2022 |
| Happy Place Homes Limited | Real estate | 2023 |
| Hard Sell Limited | Information & communication | 2017 |
| Harley Clinical Psychology Ltd | Health & social care | 2018 |
| Harlow Truck Centre Limited | Wholesale & retail | 1991 |
| Harper Moore Search Ltd | Administrative & support | 2021 |
| Harrison Plant Hire Ltd | Administrative & support | 2020 |
| Harry Holdings Ltd | Professional & scientific | 2016 |
| Harry Laud Consulting Limited | Professional & scientific | 2024 |
| Hartley Developments Limited | Real estate | 2016 |
| Hartom Construction Limited | Construction | 2024 |
| Hartwood Solutions Limited | Professional & scientific | 2025 |
| Has-Tech Air Conditioning Limited | Construction | 2020 |
| Haskins.Io Ltd | Professional & scientific | 2023 |
| Hasnaz Ltd | Hospitality | 2023 |
| Hasty Investments Ltd | Real estate | 2024 |
| Hatch Building & Construction Ltd | Construction | 2012 |
| Hatchell Ltd | Professional & scientific | 2024 |
| Hatfield Walking Squash CIC | Arts & recreation | 2025 |
| Hauhau Limited | Manufacturing | 2022 |
| Hawkforce Ltd | Administrative & support | 2025 |
| Hawkins Vehicle Leasing Limited | Administrative & support | 2013 |
| Hawksdown Holdings Limited | Financial services | 2017 |
| Hazirol Ltd | Hospitality | 2024 |
| Hcml Properties Limited | Real estate | 2025 |
| Hdays Ltd | Professional & scientific | 2017 |
| HDM Industries Ltd | Construction | 2022 |
| HDS Automotive Ltd | Wholesale & retail | 2026 |
| Health in Touch Limited | Information & communication | 2015 |
| Healthy Heals Ltd | Health & social care | 2019 |
| Hearn Heritage Holdings Ltd | Financial services | 2025 |
| Heart to Home Support Limited | Health & social care | 2025 |
| Heartbeat HR Limited | Professional & scientific | 2016 |
| Heath Plant & Commercial Ltd | Administrative & support | 2020 |
| Heavenlyhair Beauty Ltd | Other services | 2021 |
| Heavy Penguin Ltd | Professional & scientific | 2019 |
| Henford Ltd | Professional & scientific | 2018 |
| Hengrave Hall Limited | Hospitality | 2014 |
| Henry Norris Partnership LP | | 2012 |
| Heritage 6 Limited | Real estate | 2021 |
| Heritage EC1 Limited | Professional & scientific | 2023 |
| Heritage Property Rentals Limited | Real estate | 2022 |
| Heritage Share Holdings Limited | Financial services | 2022 |
| Herizen Ltd | Wholesale & retail | 2025 |
| Hertford Dentistry Ltd | Health & social care | 2021 |
| Hertford Hearing Ltd | Wholesale & retail | 2022 |
| Hertford Homes Ltd | Real estate | 2025 |
| Hertford Plumbers Limited | Construction | 2014 |
| Hertford RFC (Operations) Limited | Arts & recreation | 2016 |
| Hertford Rugby Club Ltd | Arts & recreation | 2012 |
| Hertford Rugby Football Club (Holdings) Limited | Arts & recreation | 2020 |
| Hertfordshire Loft Conversions Limited | Construction | 2025 |
| Hertfordshire Property Development Ltd | Construction | 2024 |
| Hertfordshire Smile Ltd | Financial services | 2021 |
| Hertfordshire Spanish School Ltd | Education | 2025 |
| Herts and Essex Teeth Whitening Ltd | Other services | 2022 |
| Herts Builders Limited | Construction | 2010 |
| Herts CPM Ltd | Professional & scientific | 2021 |
| Herts Developments Limited | Construction | 2016 |
| Herts Elite Cleans Limited | Administrative & support | 2023 |
| Herts Energy Ltd | Wholesale & retail | 2018 |
| Herts Horses & Ponies Ltd | Wholesale & retail | 2021 |
| Herts Investment Group Limited | Financial services | 2021 |
| Herts Landscape Supplies Limited | Administrative & support | 2014 |
| Herts Maintenance Solutions Limited | Construction | 2014 |
| Herts Mole Control Ltd | Administrative & support | 2022 |
| Herts Orthodontics Limited | Health & social care | 2008 |
| Herts Property Rentals Limited | Real estate | 2021 |
| Herts RC Models Limited | Wholesale & retail | 2010 |
| Herts Renewables Limited | Construction | 2024 |
| Herts Resourcing Group Limited | Education | 2016 |
| Herts Roofing & Property Services Ltd | Construction | 2019 |
| Herts Storage Limited | Transport & logistics | 2007 |
| Herts Tree Care Ltd | Agriculture & fishing | 2022 |