| Harform Ltd | Construction | 2026 |
| Harpfix Limited | Construction | 2016 |
| Harpscreen International Limited | Manufacturing | 1997 |
| Hartel & Co Estate Agents Ltd | Real estate | 2025 |
| Hastings Sash Windows Ltd | Construction | 2026 |
| Haughey Recruitment Ltd | Administrative & support | 2015 |
| Hawlmark Energy Limited | Energy | 2023 |
| Hawthorn Bay Company Limited | Financial services | 2022 |
| Hayden Commercial Repair Centre Ltd | Wholesale & retail | 2023 |
| Haydock Fuels Ltd | Wholesale & retail | 2020 |
| Hayes Farms | Agriculture & fishing | 2008 |
| Hayes Fuels | Wholesale & retail | 2014 |
| Hayes Fuels (Packaging & Distribution) Limited | Manufacturing | 2011 |
| Hazelton Dungannon Limited | Administrative & support | 2010 |
| Hazelton Motors Ltd | Wholesale & retail | 2013 |
| Hbsons Ltd | Other services | 2025 |
| Hcgdproperties Limited | Households | 2021 |
| Healthcare Essentials Limited | Wholesale & retail | 2008 |
| Healthy Life Supplements Ltd | Wholesale & retail | 2021 |
| Heart & Soil Health Ltd | Health & social care | 2023 |
| Heating Solutions Mechanical Ltd | Construction | 2017 |
| Heftyb Limited | Professional & scientific | 2025 |
| Hegan Biomass Ltd | Manufacturing | 2014 |
| Hegan Farms Ltd | Manufacturing | 2015 |
| Hemel Limited | Wholesale & retail | 1992 |
| Henry Freight Services Ltd | Transport & logistics | 2024 |
| Hetherington Painting & Building Contractors Ltd | Construction | 2020 |
| High Branch (JG) Ltd | Construction | 2023 |
| High Branch Group Ltd | Construction | 2023 |
| Highline Competitions Ltd | Wholesale & retail | 2020 |
| Hill Haulage Ltd | Transport & logistics | 2023 |
| Hillcrest Centre Limited | Wholesale & retail | 2001 |
| Hillkirk Eggs Ltd | Wholesale & retail | 2025 |
| Hillside Kennels Ltd | Agriculture & fishing | 2021 |
| Hilltopfabrication Ltd | Manufacturing | 2023 |
| Hiptogeek Ltd | Wholesale & retail | 2021 |
| HIT Ball Studio Ltd | Wholesale & retail | 2025 |
| HJZ Holdings Ltd | Real estate | 2026 |
| Hmac Contracts Ltd | Construction | 2017 |
| HML Studios Limited | Professional & scientific | 2020 |
| HMN Properties Ltd | | 2006 |
| Hoey Farms Limited | Agriculture & fishing | 2012 |
| Hogar Primera Ltd | Real estate | 2025 |
| Holbrad Ltd | Professional & scientific | 2020 |
| Holland Electrical Limited | Construction | 2014 |
| Home Farm Eggs Ltd | Agriculture & fishing | 2017 |
| Home Farm Mushrooms Ltd | Wholesale & retail | 2009 |
| Homes by Western Ltd | Construction | 2020 |
| Homestyle Furnishings (N.I.) Ltd | Wholesale & retail | 2020 |
| Homestyle Furnishings Ltd. | Wholesale & retail | 2019 |
| Horizon Talent Ltd | Administrative & support | 2024 |
| Horwoods Contracting Ltd | Professional & scientific | 2025 |
| House of Vixen Ltd | Wholesale & retail | 2019 |
| Houser Properties Ltd | Real estate | 2021 |
| Housing Connexions Limited | Real estate | 2001 |
| HOW NOW Consulting Limited | Professional & scientific | 2022 |
| Howden Enterprises Ltd | Agriculture & fishing | 2015 |
| HP Networks Ltd. | Information & communication | 2015 |
| HQ Welding Ltd | Professional & scientific | 2024 |
| HSE Management Consultancy Limited | Construction | 2010 |
| HTC Mechanical Services Limited | Construction | 2007 |
| HTG Deals Limited | Wholesale & retail | 2024 |
| Hucon Contracts Ltd | Construction | 2019 |
| Hucon Plant Limited | Wholesale & retail | 2025 |
| Hucon Properties Ltd | Real estate | 2022 |
| Hughes & Co Accountants Limited | Professional & scientific | 2019 |
| Hughes Attachments Limited | Extraterritorial | 2024 |
| Hughes ATV Ltd | Wholesale & retail | 2025 |
| Hughes Compost Ltd | Manufacturing | 2023 |
| Hughes Family Holdings Limited | Professional & scientific | 2015 |
| Hughes Joinery Ltd | Manufacturing | 2019 |
| Hughes Logistics and Hire Ltd | Transport & logistics | 2023 |
| Hughes Nurseries Ltd | Wholesale & retail | 2023 |
| Hughes Precision Engineering Ltd | Manufacturing | 2022 |
| Hughes Truck & Trailer Spares Ltd | Wholesale & retail | 2016 |
| Hullo Technologies Ltd | Information & communication | 2026 |
| Hydraulics (Ireland) Limited | Extraterritorial | 1970 |
| IAN Cuddy Agencies Ltd | Other services | 2006 |
| IM Mccluskey Ltd | Construction | 2003 |
| Imex Ireland Limited | Transport & logistics | 2025 |
| Immersonal Limited | Information & communication | 2021 |
| Impex Abrasives Ltd | Manufacturing | 2020 |
| Incredible Kids MID Ulster | Education | 2025 |
| Indoorout Ltd | Manufacturing | 2026 |
| Infinity Interiors Ltd | Construction | 2019 |
| Inflatable World Ltd | Arts & recreation | 2017 |
| Inland Waterways Association of Ireland (NI) Limited | Education | 2023 |
| Innest Ltd | Wholesale & retail | 2025 |
| Innishcove Management Company Limited | Households | 2021 |
| INNOV8 Electronics Ltd | Manufacturing | 2019 |
| Insight Solutions (Ireland) Ltd | Professional & scientific | 2018 |
| Inspect & Test Services Limited | Construction | 2012 |
| Intershoot Firearms Ltd | Wholesale & retail | 2016 |
| Intershoot Ranges Ltd | Wholesale & retail | 2020 |
| Invictus Group Holdings Ltd | Hospitality | 2018 |
| Invictus Properties Group Ltd | Hospitality | 2021 |
| Ipower Ireland Ltd | Wholesale & retail | 2018 |
| Irish Caving Digs Community Interest Company | Hospitality | 2024 |
| Irish Construction Limited | Construction | 2014 |
| Irish Minerals GM Limited | Manufacturing | 2013 |