| Harbinson Cairns Partnership Limited | Financial services | 2014 |
| Harbinson DEV Ltd | Information & communication | 2026 |
| Harbinson Homes Limited | Construction | 2003 |
| Harborteks Impex LP | | 2017 |
| Harbour Loft Management Company Limited | Extraterritorial | 2009 |
| Harbour View Property Management Company Limited | Households | 2004 |
| Harcon Electrical Limited | Construction | 2015 |
| Harcourt Construction (NI) Limited | Construction | 2006 |
| Harden Trust Limited | Real estate | 1958 |
| Harding Retail Ltd | Wholesale & retail | 2021 |
| Hargan Homes Limited | Construction | 2021 |
| Harimoto Tech Limited | Wholesale & retail | 2025 |
| Harjensam Ltd | Construction | 2014 |
| Harkcom Services Limited | Construction | 2025 |
| Harland and Wolff, Public Limited Company | Public administration | 1885 |
| Harland Mews Management Company Limited | Households | 1999 |
| Harlem Cafe Ltd | Hospitality | 2016 |
| Harley Foods Ltd | Hospitality | 2022 |
| Harley Todd Ltd | Wholesale & retail | 2024 |
| Harley's Day Today Ltd | Wholesale & retail | 2022 |
| Harleys Cafe Bar & Restaurant Limited | Hospitality | 2007 |
| Harmony Investing (NI) Ltd | Financial services | 2020 |
| Harmony Restaurants Limited | Hospitality | 2019 |
| Harmonyhousebelfast Limited | Manufacturing | 2024 |
| Harold Mitchell & Company Limited | Extraterritorial | 1948 |
| Harold Mitchell (Banbridge) Limited | Extraterritorial | 1965 |
| Harold Mitchell (Belfast) Limited | Financial services | 1986 |
| Harold Mitchell (Dromore) Limited | Extraterritorial | 1994 |
| Harold Mitchell Investments Limited | Real estate | 2023 |
| Harper & Harper Homes Ltd | Construction | 2017 |
| Harper Anaesthetic Services Limited | Health & social care | 2018 |
| Harper Contracts Limited | Construction | 2012 |
| Harper Tours Ltd | Administrative & support | 2023 |
| Harrier Holdco Limited | Professional & scientific | 2017 |
| Harrier Propco Limited | Real estate | 2020 |
| Harrier Real Estate (NO.1) Ltd | Real estate | 2022 |
| Harrier Real Estate (NO3) Ltd | Real estate | 2025 |
| Harrier Real Estate Ltd | Real estate | 2022 |
| Harriette Foods Ltd | Hospitality | 2018 |
| Harris & Co Wealth Management Ltd | Financial services | 2024 |
| Harris Data Science Ltd | Information & communication | 2025 |
| Harris Hall Management Company Limited | Households | 2015 |
| Harris Kilt Company Ltd | Wholesale & retail | 2018 |
| Harris Rundle Limited | Health & social care | 1931 |
| Harrisalon Limited | Real estate | 2022 |
| Harrison & Hardstaff Ltd. | Professional & scientific | 2012 |
| Harrison Bathrooms Ireland Ltd | Wholesale & retail | 2021 |
| Harrison Healthcare Ltd | Wholesale & retail | 2004 |
| Harry Noblett (1996) Limited | Wholesale & retail | 1996 |
| Harryluckypa Ltd | Wholesale & retail | 2025 |
| Harrymount Investments Ltd | Wholesale & retail | 2014 |
| Harrys Buses Ltd | Transport & logistics | 2024 |
| Hartebeest Consulting Ltd | Extraterritorial | 2015 |
| Hartech Building Services Limited | Construction | 2016 |
| Hartley Hall Apartments Management Ltd | Households | 2016 |
| Haru Ltd | Information & communication | 2017 |
| Harvest Bidco Limited | Financial services | 2021 |
| Harvest Investco Limited Partnership | | 2021 |
| Harvest Topco Limited | Financial services | 2021 |
| Harvey Norman Leasing (NI) Limited | | 2008 |
| Harvolt Limited | Manufacturing | 2015 |
| Harwen Limited | Information & communication | 2019 |
| Hasan CAN SAK Ltd | Wholesale & retail | 2024 |
| Hash Contracts Limited | Construction | 2016 |
| Hashtag Harmony Limited | Hospitality | 2024 |
| Hashtag Media Group Limited | Professional & scientific | 2023 |
| Haslam Property NI Limited | Real estate | 2019 |
| Haslem Group NO 1 Ltd | Real estate | 2025 |
| Haslett Developments Ltd | Construction | 2011 |
| Haslett Homes Ltd | Construction | 2017 |
| Haso Project Limited | Construction | 2021 |
| Hassan Dudex Ltd | Wholesale & retail | 2025 |
| Hasta Kalah Limited | Wholesale & retail | 2011 |
| Hastings Apartments Ltd | Hospitality | 2022 |
| Hastings Hotels Group Limited | Hospitality | 2023 |
| Hastings Hotels Management Limited | Hospitality | 1954 |
| HAT Logistics Ltd | Transport & logistics | 2025 |
| Hatch and Wolf Limited | Hospitality | 2024 |
| Hatch Brothers Hardware Limited | Wholesale & retail | 2017 |
| Hatch Web Design Limited | Information & communication | 2020 |
| Hatfield & Hatfield Partners Ltd | Real estate | 2025 |
| Hathor Holdings Limited | Real estate | 2021 |
| Haughey Contracts Limited | Administrative & support | 2022 |
| Haugheys Solicitors Limited | Professional & scientific | 2017 |
| Haulboline Shellfish Limited | Extraterritorial | 2007 |
| Haulvia Parcel and Logistics Ltd | Transport & logistics | 2025 |
| Haunted Media Group Ltd | Information & communication | 2024 |
| Haupt Capital Holdings NI Ltd | Financial services | 2024 |
| Haus of Deco Ltd | Wholesale & retail | 2022 |
| Hauteur Limited | Wholesale & retail | 2023 |
| Havana Grill NI Ltd | Hospitality | 2021 |
| Havana Group Limited | Financial services | 2015 |
| Havana Limited | Financial services | 2015 |
| Havana Trading NO.1 Limited | Financial services | 2015 |
| Havana Trading NO.10 Limited | Extraterritorial | 2017 |
| Havana Trading NO.2 Limited | Financial services | 2015 |
| Havana Trading NO.3 Limited | Real estate | 2015 |
| Havana Trading NO.4 Limited | Real estate | 2015 |
| Havana Trading NO.6 Limited | Extraterritorial | 2017 |
| Havana Trading NO.7 Limited | Extraterritorial | 2017 |