| Information Security Solutions Limited | Information & communication | 2000 |
| Infospeed Holdings Limited | Information & communication | 2009 |
| Infospeed Limited | Information & communication | 1981 |
| Infralec Ltd | Construction | 2019 |
| Infrapro Consulting Ltd | Professional & scientific | 2022 |
| Infyniti Properties Limited | Hospitality | 2025 |
| Ingenuity Financial Services Limited | Financial services | 2005 |
| Ingleace Limited | Health & social care | 2023 |
| Ingrams Close(Hersham)Limited | Households | 1966 |
| Inigini Limited | Wholesale & retail | 2021 |
| Initiative Property Management Ltd | Real estate | 2009 |
| Inject SET Limited | Health & social care | 2024 |
| Injective Corporation Limited | Wholesale & retail | 2025 |
| INK Vibes Limited | Manufacturing | 2026 |
| Inkitabstracts Ltd | Wholesale & retail | 2026 |
| Inline Structures Ltd | Professional & scientific | 2024 |
| Inner Earth Ltd | Health & social care | 2024 |
| Inner Freedom Limited | Health & social care | 2016 |
| Inner Vista Ltd | Health & social care | 2019 |
| Innerglow by Megan Ltd | Other services | 2026 |
| Innervision Coaching Ltd | Other services | 2012 |
| Innkerr Limited | Hospitality | 2004 |
| Innocom Group Limited | Wholesale & retail | 2026 |
| Innomotion Limited | Professional & scientific | 2018 |
| Innovare Studios Limited | Information & communication | 2018 |
| Innovation Build South Limited | Construction | 2026 |
| Innovative Business Solution & Services Ltd | Wholesale & retail | 2021 |
| Innovative Engineering Solutions Ltd | Professional & scientific | 2025 |
| Innovel Technologies Limited | Construction | 2019 |
| Innovojestic Enterprises Limited | Wholesale & retail | 2025 |
| Innvotech Systems Ltd | Information & communication | 2023 |
| Inoe Ltd | Real estate | 2016 |
| Inpromark Ltd | Wholesale & retail | 2013 |
| Insanity Gaming Arcade Limited | Arts & recreation | 2020 |
| Inside IR35 Roles Ltd | Information & communication | 2022 |
| Inside Shell Limited | Construction | 2014 |
| Inside the Odds Ltd | Information & communication | 2026 |
| Insight Commercial Property Ltd | Administrative & support | 2024 |
| Insight Consultancy and Project Management Ltd | Professional & scientific | 2019 |
| Insight Network Solutions Limited | Information & communication | 2017 |
| Insight Security & Facilities Ltd | Administrative & support | 2009 |
| Insight Security Holdings Ltd | Administrative & support | 2024 |
| Insight Special Risks Ltd | Transport & logistics | 2021 |
| Insignia Bodyworks Ltd | Wholesale & retail | 2019 |
| Inspected Limited | Wholesale & retail | 2011 |
| Inspire Heating Ltd | Construction | 2022 |
| Inspired Business Marketing Limited | Information & communication | 2005 |
| Inspired Medics Ltd | Health & social care | 2020 |
| Inspired Solutions (Software) Limited | Information & communication | 1999 |
| Inspired Traveller Limited | Professional & scientific | 2004 |
| Inspiring Vacations UK Limited | Administrative & support | 2018 |
| Inspirit Ventures Limited | Professional & scientific | 2016 |
| Instamax Ltd | Information & communication | 2017 |
| Instance in the Cloud Ltd | Information & communication | 2022 |
| Instant Ways Limited | Administrative & support | 2014 |
| Institute of Civil Funerals | Other services | 2004 |
| Instrument Product Services Limited | Manufacturing | 1989 |
| Insulation Costs International Ltd | Information & communication | 2022 |
| Insulation One Stop Limited | Construction | 2022 |
| Insulation Wise Limited | Construction | 2026 |
| Insure Group Limited | Financial services | 2012 |
| Insurepro Consultancy Ltd | Professional & scientific | 2024 |
| Intdec Ltd | Professional & scientific | 2014 |
| INTEGR8 Children's Therapy Limited | Health & social care | 2024 |
| Integripay Limited | Information & communication | 2024 |
| Integrity Build Ltd | Construction | 2016 |
| Integrity Developments Limited | Construction | 2020 |
| Integro Innovations Limited | Wholesale & retail | 2020 |
| Intelligence Augmented Ltd | Professional & scientific | 2018 |
| Intelligent Communitycations 125 Ltd | Information & communication | 2017 |
| Intellisoftware Limited | Information & communication | 1998 |
| Intentionmars Limited | Wholesale & retail | 2025 |
| Inter-Continental Car Parks (Sandbanks) Limited | Real estate | 1970 |
| Interactive Consulting Services Limited | Professional & scientific | 2009 |
| Interactive SPV LLP | | 2011 |
| Interface 24/7 Limited | Administrative & support | 2005 |
| Interior Design LAB Ltd | Wholesale & retail | 2014 |
| Interiors 1900 Ltd. | Extraterritorial | 1982 |
| Interiors by Marlaine Ltd | Professional & scientific | 2020 |
| Intermingled Ltd | Professional & scientific | 2013 |
| Internal Audit & Risk Assessment Limited | Professional & scientific | 2014 |
| International 29ER Class Association Ltd | Arts & recreation | 2022 |
| International Centre for Healthy & Safe Relationships Ltd | Information & communication | 2019 |
| International Communitysignments Ltd | Transport & logistics | 2021 |
| International Consultancy Direct Ltd | Health & social care | 2025 |
| International Engineering Company Limited | Professional & scientific | 1973 |
| International Feed Ltd | Information & communication | 2023 |
| International Health Screen Limited | Health & social care | 2020 |
| International House Bournemouth Limited | Real estate | 2009 |
| International Language Services Limited | Education | 2019 |
| International Maritime Rescue Federation | Other services | 2003 |
| International Modern Future Ltd | Transport & logistics | 2020 |
| International Sealants Limited | Manufacturing | 2025 |
| International Yacht Brokerage Limited | Wholesale & retail | 2024 |
| Internet Flooring Supplies Limited | Wholesale & retail | 2013 |
| Interstellar Dorset Ltd | Professional & scientific | 2025 |
| Intetrix Solutions Ltd | Information & communication | 2025 |
| Into Oneness Ltd | Financial services | 2019 |
| Into the Groom Ltd | Other services | 2022 |
| Intshade Ltd | Construction | 2024 |