| Twinkle Cottage Day Nursery Ltd | Education | 2010 |
| Twinspire ME Ltd | Wholesale & retail | 2020 |
| Twistedpair Limited | Information & communication | 2004 |
| Two Little Wonders Ltd | Wholesale & retail | 2025 |
| Two Two Barafundle Ltd | Construction | 2024 |
| Two Two Projects Ltd | Construction | 2013 |
| TWO1CREATIVE Agency Limited | Professional & scientific | 2019 |
| TWO1HOMES Limited | Real estate | 2023 |
| Twomey Development Group Ltd | Financial services | 2024 |
| Twomey Property Group Ltd | Real estate | 2019 |
| TWP Media Limited | Financial services | 2025 |
| Twyford 1932 Limited | Real estate | 2017 |
| Twyford Pharmaceutical Services Limited | Health & social care | 2006 |
| Twyford Recycling Limited | Water & waste | 2019 |
| Twylight Limited | Real estate | 1999 |
| TY UK Limited | Wholesale & retail | 2005 |
| Tybw Ltd | Professional & scientific | 2025 |
| TYC Arts & Education CIC | Education | 2025 |
| Tygo Projects Ltd | Construction | 2025 |
| Tyre Blade Holdings Limited | Financial services | 2023 |
| Tyre Blade Limited | Manufacturing | 2023 |
| Tyrone GUY Limited | Construction | 2006 |
| U Connect Services Limited | Transport & logistics | 2012 |
| U D Roofing Limited | Construction | 2018 |
| U-Fit & We-Fit Ltd | Construction | 2014 |
| Ua-Pro Limited | Wholesale & retail | 2022 |
| Ubahcrops Ltd | Wholesale & retail | 2025 |
| Uddins Medical Ltd | Health & social care | 2021 |
| Ufodrive Limited | Wholesale & retail | 2019 |
| Ufofleet UK Limited | Financial services | 2022 |
| Ugas E-Commerce Limited | Wholesale & retail | 2024 |
| UK Car Importation Ltd | Wholesale & retail | 2025 |
| UK Films International Limited | Professional & scientific | 2020 |
| UK Fusion Specialist Ltd | Hospitality | 2017 |
| UK Pharmacy College Ltd | Administrative & support | 2020 |
| UK Property Lettings Ltd | Real estate | 2017 |
| UK SMART2 Limited | Transport & logistics | 2023 |
| UK Valet Supplies Ltd | Wholesale & retail | 2025 |
| UK Watch Trade Ltd | Wholesale & retail | 2018 |
| Ukeli Ltd | Manufacturing | 2026 |
| Ulinkey Ltd | Wholesale & retail | 2023 |
| Ultimate Care Agency Limited | Health & social care | 2016 |
| Ultimate Decor Limited | Construction | 2022 |
| Ultimate Event Magic Limited | Arts & recreation | 2014 |
| Ultimate FS Ltd | Administrative & support | 2026 |
| Ultimate Heathcare Supplies Limited | Health & social care | 2023 |
| Ultra Cloud Consulting Ltd | Information & communication | 2026 |
| Ultraviolet Investment Co Ltd | Wholesale & retail | 2023 |
| Ulysses (2000) Limited | Administrative & support | 1997 |
| Unbeatable Rates Ltd | Wholesale & retail | 2024 |
| Unburdened Utilities Ltd | Administrative & support | 2026 |
| Uncletomschillis Ltd | Agriculture & fishing | 2021 |
| Uncut Investments Ltd. | Financial services | 1998 |
| Under the Hard HAT Limited | Manufacturing | 2026 |
| Undercover Skatepark Project Community Interest Company | Arts & recreation | 2019 |
| Underground Signs & Graphics Ltd | Construction | 2025 |
| Underground Soiree Limited | Information & communication | 2024 |
| Understood Solutions Ltd | Professional & scientific | 2007 |
| Underwater Limited | Information & communication | 2019 |
| Unforgettable Luncheon Ltd | Hospitality | 2022 |
| Unicorns ARE Real Limited | Transport & logistics | 2018 |
| Unify HQ Limited | Administrative & support | 2017 |
| Union Developments (IW) Limited | Real estate | 2014 |
| Union Scribe Ltd | Administrative & support | 2026 |
| Unique Flooring Solutions Portsmouth Ltd | Construction | 2026 |
| Unique Global Sports Limited | Arts & recreation | 2025 |
| Unique Planters Limited | Extraterritorial | 2015 |
| Unique Properties Southern Ltd | Real estate | 2025 |
| United Car Centre Ltd | Wholesale & retail | 2013 |
| United INK UK Platinum Tattoo Lounge Ltd | Health & social care | 2018 |
| United Kingdom Offshore Boating Association Limited | Arts & recreation | 1995 |
| United Long Banners Investment Co. Ltd | Extraterritorial | 2008 |
| Unitk Ltd | Administrative & support | 2018 |
| Universal Cart Limited | Wholesale & retail | 2026 |
| Universal Food Supplies Limited | Wholesale & retail | 2022 |
| University of Portsmouth Enterprise Limited | Professional & scientific | 1989 |
| University of Portsmouth Investments Limited | Professional & scientific | 1994 |
| University of Portsmouth Services Limited | Health & social care | 2006 |
| Unknown Entertainment Ltd | Wholesale & retail | 2021 |
| Unlimited Firm Ltd | Wholesale & retail | 2022 |
| Unloc Consulting Limited | Education | 2022 |
| Unloc Learning Limited | Education | 2013 |
| Unlocksuccess Limited | Education | 2014 |
| Unwind Health and Beauty Limited | Other services | 2022 |
| UOP Academic Services Limited | Education | 2022 |
| UP 4 Access Limited | Construction | 2009 |
| UP and Running (Sports Injury Clinics) Ltd | Health & social care | 2009 |
| Upix Photography Limited | Professional & scientific | 2003 |
| Upland Homes Ltd | Real estate | 2018 |
| Uplifting Aviation Limited | Wholesale & retail | 2002 |
| Uproperty Limited | Real estate | 2024 |
| Upton Asset Management Limited | Professional & scientific | 2023 |
| Urban Developments (Gosport) Ltd | Construction | 2013 |
| Urban Glass Limited | Construction | 2026 |
| Urban Installers Ltd | Construction | 2015 |
| Urban Interiors Southern Ltd | Construction | 2019 |
| Urban Island Brewing Co. Limited | Manufacturing | 2014 |
| Urban PAD Properties Limited | Households | 2014 |
| Urban South Ltd | Construction | 2023 |
| Urbanowl Limited | Wholesale & retail | 2024 |