| Houndagrips Ltd | Wholesale & retail | 2021 |
| House of Alignment Ltd | Wholesale & retail | 2026 |
| House of Becks Ltd | Wholesale & retail | 2025 |
| Houseofvaltrading Limited | Wholesale & retail | 2026 |
| Housing Communities Wales Limited | Construction | 2020 |
| Howard Engineering & Maintenance Limited | Wholesale & retail | 1984 |
| Howbro Brickwork Ltd | Construction | 2019 |
| Howells Developments Limited | Real estate | 2026 |
| HPM Stratford Limited | Professional & scientific | 2014 |
| HRP Refrigerants Limited | Extraterritorial | 1996 |
| HRS Corporation Ltd | Administrative & support | 2019 |
| HSE Training Solutions Ltd | Transport & logistics | 2012 |
| Hshk LLP | | 2024 |
| Huaxiaolong Ltd | Wholesale & retail | 2022 |
| Huayang Trading Co., Ltd | Wholesale & retail | 2025 |
| Hughes Flooring Limited | Construction | 2017 |
| Hughes Homes Development Limited | Real estate | 2020 |
| Hughleon Controls Ltd | Professional & scientific | 2011 |
| Hunky Dory Production Ltd | Information & communication | 2018 |
| Hutchings Group Holdings Ltd | Financial services | 2017 |
| HUW John & Co Limited | Professional & scientific | 2003 |
| HVA Ltd | Wholesale & retail | 2025 |
| Hydrodragon (London) Limited | Wholesale & retail | 2008 |
| Hyggehub Ltd | Wholesale & retail | 2023 |
| Hyke Corner Creative Ltd | Professional & scientific | 2023 |
| I & B Jones Limited | Wholesale & retail | 1975 |
| I J Properties SW Ltd | Real estate | 2020 |
| I Like Cake Limited | Households | 2016 |
| I-Deal Cars (Newport) Ltd | Wholesale & retail | 2019 |
| I-Kan Fitness Ltd | Arts & recreation | 2018 |
| I.A.J Properties Limited | Real estate | 2025 |
| IAN & Lesley Property Solutions Limited | Real estate | 2021 |
| IAN D Campbell Independent Financial Services Limited | Financial services | 2017 |
| IAN Power Solutions IPS Ltd | Construction | 2015 |
| Idols Trading Limited | Other services | 2020 |
| Iles Renovations Property Services Ltd | Construction | 2026 |
| IM Interim Management Ltd | Professional & scientific | 2007 |
| Imago Print & Design Ltd | Manufacturing | 2011 |
| Imds Operations Ltd | Wholesale & retail | 2025 |
| IMG Clay Products Limited | Construction | 2024 |
| Impactful INK Ltd | Professional & scientific | 2025 |
| Incisive Oral Solutions Limited | Health & social care | 2017 |
| Indextransport Ltd | Transport & logistics | 2023 |
| Infinity Plumbing Wales Ltd | Construction | 2020 |
| Infinity Smart Homes Limited | Construction | 2023 |
| Infoearth Tech Ltd | Transport & logistics | 2023 |
| Inforreel CIC | Wholesale & retail | 2025 |
| Infracivi Ltd | Construction | 2014 |
| Inject Aesthetics by Chloe Thomas Limited | Other services | 2024 |
| Innermachines Ltd | Professional & scientific | 2020 |
| Innover Technologies Co. Ltd. | Extraterritorial | 2016 |
| Innovia Consulting Limited | Professional & scientific | 2021 |
| Innovia Group Ltd | Professional & scientific | 2024 |
| Innovia Metal Solutions Ltd | Manufacturing | 2024 |
| Innovizen Tech Limited | Wholesale & retail | 2023 |
| INOV8 Properties Limited | Construction | 2019 |
| Inside Edge Developments Ltd | Construction | 2018 |
| Inside Edge Lettings Ltd | Real estate | 2022 |
| Insight Training Academy Ltd | Education | 2023 |
| Inspirational Futures Well-Being Support Ltd | Education | 2020 |
| Inspire ME Fashion Ltd | Real estate | 2013 |
| Inspired Machine Ltd | Information & communication | 2016 |
| Insulation South Wales Limited | Construction | 2019 |
| Inteclads Technology Solutions Ltd | Information & communication | 2023 |
| Integrity Life Solutions Limited | Financial services | 2012 |
| Integrity Protect Group Limited | Financial services | 2015 |
| Integrity Protect NO 1 Limited | Financial services | 2015 |
| Integrity Protect NO 2 Limited | Financial services | 2015 |
| Intelle Construction Limited | Construction | 2013 |
| Inter Alps Transfers Limited | Real estate | 2013 |
| Inter-Haul (Swindon) Limited | Transport & logistics | 2017 |
| Inter-Haul Pallet Services Ltd. | Transport & logistics | 2001 |
| Interlink RCT | Administrative & support | 2011 |
| International Commercial and Business Finance Ltd | Financial services | 2009 |
| International Hyperoxide Corporation Limited | Professional & scientific | 2014 |
| Intrado Ltd | Construction | 2006 |
| Intruserv Ltd | Professional & scientific | 2023 |
| Intuflux Ltd | Professional & scientific | 2025 |
| Inventory Plus Wales Ltd | Other services | 2024 |
| Involve Building Projects Ltd | Construction | 2020 |
| Involve Property Management Ltd | Real estate | 2014 |
| Involve Rail Ltd | Administrative & support | 2015 |
| Involve Recruitment Holdings Limited | Professional & scientific | 2020 |
| Involve Recruitment Limited | Administrative & support | 2013 |
| Involve Recruitment Midlands Ltd | Administrative & support | 2019 |
| Involve Recruitment North Ltd | Administrative & support | 2019 |
| Involve Recruitment South West Limited | Administrative & support | 2009 |
| Involve Recruitment Trustee Limited | Professional & scientific | 2023 |
| Involve Residential Property Ltd | Real estate | 2015 |
| Ionic Plumbing & Heating Limited | Construction | 2020 |
| IPR Consulting Ltd | Professional & scientific | 2024 |
| Iron Circle 24 Limited | Education | 2024 |
| ISH Ltd | Hospitality | 2026 |
| Isher Homes Limited | Other services | 2024 |
| ISO Auditing Limited | Professional & scientific | 2025 |
| ISO Services (Sheq) Ltd. | Professional & scientific | 2018 |
| Isolumen Limited | Extraterritorial | 2009 |
| Isource Rail Engineering Ltd | Construction | 2019 |
| Istanbul Kebab Ltd | Hospitality | 2025 |
| ISW & Sons Ltd | Construction | 2018 |