| H & M Services - Energy Solutions Limited | Manufacturing | 2011 |
| H H Homes Limited | Real estate | 2010 |
| H R a Holdings Ltd | Financial services | 2016 |
| H Wilson & Sons Limited | Construction | 2017 |
| H&C (N.I.) Limited | Real estate | 2018 |
| H2 Developments Ltd | Construction | 2011 |
| Habitat for Humanity Ireland Ltd | Administrative & support | 1994 |
| Hackily Limited | Professional & scientific | 2019 |
| Hainon Aero Quality Services Ltd | Professional & scientific | 2023 |
| Hainon Engineering Ltd | Manufacturing | 2019 |
| Hair Parlour Ltd | Other services | 2021 |
| Haldane Homes Limited | Real estate | 2025 |
| Hall & Associates (Marketing) N I Limited | Manufacturing | 2020 |
| Hall Homes Ltd | Construction | 2023 |
| Halo Clinic Limited | Health & social care | 2025 |
| Halo Hero Ltd | Manufacturing | 2025 |
| Hampton Furnishing and Interiors Limited | Real estate | 1992 |
| Handling and Storage Equipment Company Limited | Manufacturing | 1967 |
| Handscopu Ltd | Wholesale & retail | 2026 |
| Handy Ireland Ltd | Wholesale & retail | 2020 |
| Handy Stuff Company Limited | Wholesale & retail | 2019 |
| Hanna & Hutchinson Consulting Engineers Ltd | Professional & scientific | 2011 |
| Hapert Capital LP | | 2015 |
| Happy Days Lisburn Ltd | Arts & recreation | 2021 |
| Happy Peanut Ltd | Professional & scientific | 2020 |
| Happyjobsni Ltd | Professional & scientific | 2020 |
| Hard Sums Technologies Limited | Manufacturing | 2020 |
| Hardware and Fixings Ltd | Wholesale & retail | 2021 |
| Harper Moss Ltd | Wholesale & retail | 2026 |
| Harris Stocktaking Systems Ltd | Administrative & support | 2016 |
| Harrison Construction Services Ltd | Construction | 2020 |
| Haughey Electrical Limited | Construction | 2018 |
| Haughey Farming Limited | Agriculture & fishing | 2023 |
| Haughey Group Ltd | Financial services | 2025 |
| Hawkins Construction (2025) Ltd | Construction | 2025 |
| Hawthorn Hall Lisburn Management Limited | Households | 2021 |
| Hazel Terrace Company Limited | Extraterritorial | 2019 |
| Head Studio Lisburn Ltd | Other services | 2026 |
| Healthsoft Solutions Limited | Information & communication | 2002 |
| Heanen, Stanfield & Mckee Limited | Professional & scientific | 2010 |
| Heart (NI) Ltd | Health & social care | 2014 |
| Heavy Smash Salvage LP | | 2018 |
| Hegarty QS Ltd | Professional & scientific | 2022 |
| Helen Mcdaniel Portrait Studio Limited | Professional & scientific | 2021 |
| Helios Strategies LP | | 2025 |
| Henesis (NI) Limited | Manufacturing | 2014 |
| Henley Forklift Group (N.I.) Ltd | Wholesale & retail | 2002 |
| Henry Auctioneers and Valuers Limited | Wholesale & retail | 2025 |
| Hepa Properties Limited | Construction | 2023 |
| Herokepp Ltd | Wholesale & retail | 2026 |
| Herron Software Ltd | Information & communication | 2022 |
| Hexa Services Limited | Agriculture & fishing | 1994 |
| Hh(Ni) Ltd | Other services | 2024 |
| Hhgb Properties Limited | Real estate | 2021 |
| Hi-Tech Tooling NI Ltd | Professional & scientific | 2018 |
| Hickland Agencies Limited | Wholesale & retail | 2016 |
| Hickland Cycles Ltd | Wholesale & retail | 2013 |
| Hico Group Ltd | Hospitality | 2020 |
| High Market Management LLP | | 2017 |
| Highercloud Ltd | Information & communication | 2021 |
| Highway Safety & Construction Training Ltd | Health & social care | 2016 |
| Hillsborough & District Motor Cycle Club Limited | Arts & recreation | 1968 |
| Hillsborough Financial Management Ltd | Financial services | 2021 |
| Hillsborough Tile & Bathroom Limited | Wholesale & retail | 2012 |
| Hillside Agri Ltd | Manufacturing | 2018 |
| Hilltop Designer Radiators Ltd | Manufacturing | 2022 |
| Hinch Distillery Holdings Limited | Manufacturing | 2018 |
| Hinch Distillery Limited | Manufacturing | 2016 |
| Hinch Whiskey Company Limited | Manufacturing | 2018 |
| Hinchtech Limited | Manufacturing | 2024 |
| Hireachni Ltd | Administrative & support | 2024 |
| Hireachni Solar Ltd | Administrative & support | 2026 |
| HK Bloodstock Ltd | Other services | 2013 |
| HK Deemore Industry Limited | Wholesale & retail | 2026 |
| HMA Ecom Limited | Wholesale & retail | 2024 |
| HML Downey Accountants Limited | Professional & scientific | 2022 |
| Hoist Projects Ltd | Construction | 2012 |
| Holden Bros. Ltd | Information & communication | 2023 |
| Holly Lodge Management Company (NI) Ltd | Households | 2012 |
| Holmes Scifi Publishing Ltd | Information & communication | 2018 |
| Home Protection Services (Ireland) Limited | Construction | 2010 |
| Home-Start Lisburn/Colin | Professional & scientific | 2009 |
| Honest Rentals Ltd | Administrative & support | 2026 |
| Hongkong Surwin Limited | Wholesale & retail | 2026 |
| Hopesprings IP Limited | Financial services | 2025 |
| Hornbill Consulting Limited | Professional & scientific | 2017 |
| Hornsby Haulage Ltd | Transport & logistics | 2022 |
| Hotdoggitty Limited | Hospitality | 2021 |
| House of Comps Limited | Arts & recreation | 2025 |
| House of Seris Ltd | Other services | 2018 |
| House of the Rising Sun Ltd | Real estate | 2025 |
| House of Vic-Ryn Trust Limited - the | Other services | 2007 |
| Houtpkat Ltd | Wholesale & retail | 2026 |
| HPS (Belfast) Limited | Construction | 2014 |
| HQ Racing Ltd | Arts & recreation | 2019 |
| Hqhc Limited | Other services | 2024 |
| HSI Group Limited | Professional & scientific | 1990 |
| HSI Thermal Technology Limited | Professional & scientific | 2019 |
| Hub Display Ltd | Manufacturing | 2013 |
| Hukic Limited | Wholesale & retail | 2024 |