| Harriette Properties Ltd | Real estate | 2022 |
| Harris Rides Ltd | Arts & recreation | 2024 |
| Harris-Mayes 4X4 Ltd | Wholesale & retail | 2018 |
| Harron Car Transport Limited | Administrative & support | 2002 |
| Harrow Healthcare Services Ltd | Health & social care | 2021 |
| Harrow Minibus & Coach Hire Limited | Transport & logistics | 2017 |
| Harrow Property Group Limited | Real estate | 2018 |
| Harrow Windows Limited | Construction | 2015 |
| Harry James Finance Ltd | Wholesale & retail | 2022 |
| Harry SOM Legal Limited | Professional & scientific | 2025 |
| Hartsbourne Gardens (Bushey Heath) Management Company Limited | Households | 1983 |
| Harvard Power Systems Limited | Administrative & support | 2019 |
| HAS Catering London Ltd | Hospitality | 2025 |
| Haste Electrical Ltd | Construction | 2025 |
| Hatesa Ltd | Hospitality | 2024 |
| Hayat Learning Ltd | Education | 2022 |
| Hayat Paediatric Therapy Ltd | Health & social care | 2022 |
| Haystack Design Ltd | Professional & scientific | 2011 |
| Hazard Evaluation UK Limited | Information & communication | 2023 |
| Hazelbank Estates Limited | Households | 2007 |
| Hbclearance Limited | Water & waste | 2025 |
| Hcos Solutions Ltd | Professional & scientific | 2018 |
| Hcsh Limited | Professional & scientific | 2015 |
| HCT Holdings Ltd | Construction | 2017 |
| Hdrepair Ltd | Wholesale & retail | 2025 |
| HDW Developments Limited | Construction | 2016 |
| HE Makes, SHE Creates Ltd | Manufacturing | 2023 |
| HEA7Y Limited | Professional & scientific | 2023 |
| Health & Pharma Ltd | Professional & scientific | 2023 |
| Healthedge Group Ltd | Education | 2024 |
| Heart Home Design Ltd | Wholesale & retail | 2025 |
| Heat Plus UK GAS Ltd | Construction | 2014 |
| Hebziba Consultancy Ltd | Professional & scientific | 2020 |
| Hedges Way Management Company Limited | Households | 2010 |
| Heelca Limited | Wholesale & retail | 2026 |
| Helion Group Ltd | Administrative & support | 2026 |
| Helios Academy Limited | Education | 2025 |
| Helm-International Limited | Financial services | 2025 |
| Hemlock Properties Ltd | Real estate | 2022 |
| Hemoniyan Limited | Real estate | 2017 |
| Henley's Consultancy Ltd | Professional & scientific | 2022 |
| Henley's Fitness Ltd | Arts & recreation | 2022 |
| Henry Hogan Ltd | Manufacturing | 2022 |
| Hera Health Ltd | Health & social care | 2025 |
| Herbal Health Beauty Ltd | Health & social care | 2022 |
| HERE2HEAR Ltd | Health & social care | 2020 |
| Hernz Electrical Services Limited | Construction | 2016 |
| Heron Financial Limited | Financial services | 2011 |
| Heron Financial North East Limited | Administrative & support | 2021 |
| Heronsgate Motor Group Limited | Financial services | 2025 |
| Heronsmere Home Care Ltd | Health & social care | 2015 |
| Hertfordshire Construction Services Ltd | Construction | 2025 |
| Hertfordshire Steel Limited | Manufacturing | 2022 |
| Hertfordshire Tiles and Bathrooms Ltd | Construction | 2019 |
| Herts Digital Solution Ltd | Information & communication | 2026 |
| Herts Emergency Plumbers 24/7 Ltd | Construction | 2024 |
| Herts Health and Safety Ltd | Professional & scientific | 2018 |
| Hestia Stays Ltd | Real estate | 2025 |
| Hetsgo Limited | Professional & scientific | 2021 |
| HGM Restaurants Limited | Hospitality | 2014 |
| Hidden EYE Services Ltd | Administrative & support | 2018 |
| High House Farm Trading Limited | Professional & scientific | 2006 |
| Highbrow PMU Limited | Other services | 2022 |
| Highfield Properties (ST Neots) Ltd | Real estate | 2013 |
| Hightec Rigging and Scaffolding Services Ltd | Construction | 2022 |
| Hill Farm (Phase Two) Management Company Limited | Administrative & support | 2010 |
| Hillpoint Management Company Limited | Households | 2000 |
| Hillside Grove Limited | Real estate | 2025 |
| Hillview Capital Ltd | Real estate | 2021 |
| Himmense Limited | Health & social care | 2020 |
| Hintongreen Limited | Construction | 1995 |
| Hirehub Recruitment Ltd | Administrative & support | 2025 |
| Historic Metal Detecting Limited | Arts & recreation | 2023 |
| HJ Clientkicks Ltd | Wholesale & retail | 2023 |
| Hkcpi Limited | Real estate | 2022 |
| HM Consultancy Services Limited | Professional & scientific | 2020 |
| HMS Consulting Ltd | Professional & scientific | 2013 |
| HN Associates Limited | Professional & scientific | 2018 |
| HNS Consultancy Ltd | Public administration | 2025 |
| Hobden Consulting Ltd | Arts & recreation | 2024 |
| Hodkinson Consultancy Ltd | Professional & scientific | 1999 |
| Hodkinson Consultancy Trustees Limited | Administrative & support | 2021 |
| Holding Hearts Psychology Ltd | Education | 2023 |
| Holiday Club Staycation Limited | Other services | 2021 |
| Hollands Commercial Holdings Ltd | Real estate | 2025 |
| Hollowtree Mews Management Company Limited | Construction | 2015 |
| Hollybush Montessori Limited | Education | 2016 |
| Homdor Ltd | Manufacturing | 2019 |
| Home Counties Clinics Limited | Wholesale & retail | 2006 |
| Home Counties Lawn Service Limited | Administrative & support | 2007 |
| Home County Equestrian Limited | Agriculture & fishing | 2018 |
| Home Solutions Direct Ltd | Administrative & support | 2026 |
| Homebook Limited | Information & communication | 2023 |
| Homefield Road (Chorleywood) Management Company Limited | Real estate | 2011 |
| Homoud Europe Limited | Hospitality | 2020 |
| Hopcroft Property Experts Ltd | Real estate | 2023 |
| Hope and Chance | Other services | 2009 |
| Hopej Consulting Ltd | Other services | 2025 |
| Horcos Limited | Professional & scientific | 2021 |
| Horizon Hudson Holdings Ltd | Financial services | 2018 |