| THE Winchester Tutor Ltd | Education | 2019 |
| THE Windgap Partnership LLP | | 2019 |
| THE Wine Barn Limited | Wholesale & retail | 1998 |
| THE Wish Transfers Limited | Transport & logistics | 2024 |
| Thea Willmott Design Ltd | Professional & scientific | 2023 |
| Thealcha Limited | Agriculture & fishing | 2015 |
| Theanaestheticgroup Limited | Health & social care | 2008 |
| Theatre Place Management Company Limited | Households | 2010 |
| Thecoffeygroup Limited | Construction | 2013 |
| Thegiftfinders Ltd | Wholesale & retail | 2021 |
| Themescene Limited | Professional & scientific | 2013 |
| Theonly Ltd | Professional & scientific | 2024 |
| Therapy, Coaching and Consulting Services Limited | Professional & scientific | 2022 |
| Thermal Marine Limited | Construction | 2022 |
| THF Projects Limited | Extraterritorial | 2015 |
| Think Club Ltd | Wholesale & retail | 2016 |
| Think Code Ltd | Information & communication | 2018 |
| Think Creative Consultants Limited | Professional & scientific | 2000 |
| Think Creative Limited | Extraterritorial | 2001 |
| Think Henry Limited | Professional & scientific | 2023 |
| Thinkers Ltd | Information & communication | 2007 |
| Thinking & Writing Ltd | Education | 2021 |
| Thomas and Bassett Limited | Real estate | 2024 |
| Thompson & Freemantle Limited | Construction | 2013 |
| Thompson Agri Solutions Limited | Professional & scientific | 2006 |
| Thorburn Mcalister Executive Search & Board Effectiveness Ltd | Professional & scientific | 2021 |
| Thorp Construction Limited | Construction | 2022 |
| Thorp Contracts Ltd | Construction | 2023 |
| Three Bees Creative Ltd | Administrative & support | 2022 |
| Three C'S Contract Catering Consultancy Ltd | Professional & scientific | 2025 |
| Three Circles Psychology Limited | Health & social care | 2026 |
| Three Maids Leisure Limited | Construction | 2024 |
| Three Maids Property LLP | | 2020 |
| Three of Swords Ltd | Other services | 2023 |
| Three Simple Rules Ltd | Information & communication | 2024 |
| Three Valley Construction Limited | Construction | 2006 |
| Threedom Haven Ltd | Manufacturing | 2025 |
| Threefold Sustainability Ltd | Professional & scientific | 2018 |
| Threelance Consulting Limited | Professional & scientific | 2004 |
| Thrushbridge Limited | Professional & scientific | 1981 |
| Thud Limited | Wholesale & retail | 2015 |
| Thuilliez Consultancy Services Limited | Professional & scientific | 2023 |
| Thunder Investments Limited | Financial services | 2015 |
| Thursday Studio Winchester Limited | Professional & scientific | 2023 |
| Thyrel Ltd | Wholesale & retail | 2025 |
| Tidal Current Electrical Limited | Construction | 2021 |
| Tidal Studio Limited | Professional & scientific | 2023 |
| Tidal Swim Club Ltd | Education | 2025 |
| Tiddled Limited | Manufacturing | 2026 |
| Tigers 23 Ltd | Transport & logistics | 2014 |
| Tiglios Ltd. | Professional & scientific | 2009 |
| Tigris International Wholesale Limited | Manufacturing | 2014 |
| Tilecroft Limited | Construction | 1993 |
| Tilly Masterson and Company 1 Limited | Administrative & support | 2014 |
| Tilly Masterson and Company 6 Limited | Administrative & support | 2014 |
| Tilly Masterson and Company a Limited | Administrative & support | 2015 |
| Tilly Masterson and Company Limited | Administrative & support | 2003 |
| TIM Butcher Audio Limited | Information & communication | 2003 |
| Timberscapes Ltd | Manufacturing | 2024 |
| TIME4SERVICE Limited | Other services | 2021 |
| Tinder Consulting Ltd | Professional & scientific | 2011 |
| Tiny Tea Society Ltd | Professional & scientific | 2024 |
| TIP Mate Ltd | Information & communication | 2024 |
| TIP Top Bodyworks Ltd | Wholesale & retail | 2020 |
| Tires 4 Less Limited | Extraterritorial | 1994 |
| Tiro Group Ltd | Administrative & support | 2021 |
| Titchfield Grange (Segensworth) Management Company Limited | Households | 2005 |
| Tjubi A.O Consulting Limited | Professional & scientific | 2010 |
| TK Construct Limited | Construction | 2025 |
| TM Mgmt Ltd | Information & communication | 2021 |
| TMC Research Limited | Professional & scientific | 2020 |
| Tmrw Hotels Limited | Other services | 2021 |
| TMW Holdings Limited | Financial services | 2018 |
| Toast (Southern) Limited | Administrative & support | 2017 |
| Toast and Tea Ltd | Education | 2020 |
| Toast Functions Limited | Education | 2014 |
| Toast Winchester Limited | Hospitality | 2024 |
| Toby Privett Ltd | Information & communication | 2023 |
| Tock Software Ltd | Information & communication | 2023 |
| Tollington Deyes Ltd | Information & communication | 2009 |
| TOM Davidson Limited | Professional & scientific | 2006 |
| TOM Dickson Ltd | Professional & scientific | 2002 |
| TOM Hajek Consulting Limited | Professional & scientific | 2018 |
| TOM Lamb Property Advisors Limited | Real estate | 2022 |
| TOM Waldron Engineering Services Ltd | Professional & scientific | 2024 |
| Tomolly Investments Limited | Administrative & support | 2017 |
| Tony Brown Accountancy Solutions Limited | Professional & scientific | 2018 |
| Tony Langridge Consulting Limited | Professional & scientific | 2011 |
| TONY3000 Limited | Manufacturing | 2015 |
| Toolmax General Engineering Limited | Manufacturing | 1977 |
| Toor Estates Ltd | Real estate | 2018 |
| Top Marketing UK Ltd | Professional & scientific | 2004 |
| Total OPS Hospitality Ltd | Information & communication | 2026 |
| Total Trade Services Ltd | Construction | 2020 |
| Totally Human Ltd | Information & communication | 2021 |
| Tour in Order Ltd | Arts & recreation | 2022 |
| Town Quay Developments Limited | Construction | 2004 |
| Townley Services Limited | Professional & scientific | 2018 |
| Townlocal Property Management Limited | Households | 1990 |
| Track-Iii Ltd | Professional & scientific | 2026 |