| Commodities Global Link Limited | Administrative & support | 2026 |
| Commschanger Limited | Extraterritorial | 2025 |
| Communia - Critical Social Research | Information & communication | 2023 |
| Community Cycle Centre CIC | Manufacturing | 2013 |
| Company of Makers (HQ) CIC | Education | 2011 |
| Company of Makers Ltd | Wholesale & retail | 2010 |
| Compasuk Ltd | Wholesale & retail | 2019 |
| Competitive Edge Property Consultants Ltd | Real estate | 2018 |
| Competitive Edge Property Management Ltd | Households | 2024 |
| Competitive Edge Wealth Creation Ltd | Administrative & support | 2017 |
| Compton Court RTM Company Limited | Households | 2007 |
| Computare Limited | Professional & scientific | 2000 |
| Computicks Ltd | Professional & scientific | 2009 |
| Comsa Trans Limited | Transport & logistics | 2021 |
| Concept APC Limited | Construction | 2012 |
| Concrete Roses Studios Ltd | Arts & recreation | 2025 |
| Confido Estate Ltd | Real estate | 2025 |
| Connaught Court Management Limited | Households | 2020 |
| Connect Group Specialists Ltd | Administrative & support | 2023 |
| Conquest Vaults Limited | Manufacturing | 2023 |
| Conservative Mental Health Group Ltd | Other services | 2022 |
| Consus Energy Limited | Energy | 2025 |
| Context Research Ltd | Information & communication | 2012 |
| Contract Killers Pest Control Limited | Agriculture & fishing | 2004 |
| Cool Mechanic Limited | Wholesale & retail | 2025 |
| Coombes Property Limited | Real estate | 2022 |
| Coparent AI Ltd | Information & communication | 2025 |
| Copper Renovations Ltd | Construction | 2023 |
| Copthorne Management Consultants Ltd | Professional & scientific | 2013 |
| Coral Leadership Limited | Professional & scientific | 2010 |
| Coresafe Systems Ltd | Construction | 2026 |
| Cornerstone Roofing Hampshire Ltd | Construction | 2025 |
| Coronation House Portsmouth Limited | Households | 2005 |
| Cosmic RAY Marketing Ltd | Professional & scientific | 2022 |
| Cosy Nest Florals Ltd | Wholesale & retail | 2022 |
| Cosy Nest Interiors Limited | Wholesale & retail | 2020 |
| Cottage Spice Ltd | Hospitality | 2024 |
| Could YOU Just Tech Ltd | Information & communication | 2025 |
| Country Pantry Ltd | Hospitality | 2018 |
| Country View Home Additions Limited | Construction | 2008 |
| Courtx Ltd | Arts & recreation | 2013 |
| Covindale House Management Company Limited | Households | 1991 |
| CPV Portsmouth Ltd | Administrative & support | 2025 |
| CR Consultants Limited | Professional & scientific | 2023 |
| CR Transport Elite Limited | Transport & logistics | 2025 |
| Craneswater Consulting LLP | | 2023 |
| Craneswater International Ltd | Professional & scientific | 2019 |
| Craneswater Mechanical Services Limited | Construction | 2008 |
| Crate & Apple Limited | Hospitality | 2025 |
| CRE8 Roofing & Cladding Limited | Construction | 2017 |
| Create Architectural & Design Services Limited | Professional & scientific | 2005 |
| Creative Digital Design Limited | Information & communication | 2012 |
| Creative Edge VA Ltd | Administrative & support | 2019 |
| Crescent Community Care Services Limited | Health & social care | 1999 |
| Cresta Healthcare II Ltd | Administrative & support | 2024 |
| Cresta Healthcare Ltd | Health & social care | 2020 |
| Crestcrown Limited | Administrative & support | 2009 |
| Crisitan Limited | Construction | 2024 |
| Crispindrake Ltd | Real estate | 2023 |
| Crocker Hill Properties Ltd | Real estate | 2025 |
| Crossfit Chichester Limited | Arts & recreation | 2013 |
| Crown Care Solutions Ltd | Health & social care | 2022 |
| Crownhare UK Ltd | Wholesale & retail | 2025 |
| Croxtons Holdings Limited | Financial services | 2026 |
| Croxtons Southsea Limited | Hospitality | 2017 |
| Crushed & Cured Ltd | Wholesale & retail | 2022 |
| Cspl Property Holdings Limited | Real estate | 2023 |
| CT Compton Limited | Hospitality | 2023 |
| Cudco Ltd | Administrative & support | 2022 |
| Cudco SE Ltd | Health & social care | 2026 |
| Cudco SWE Ltd | Administrative & support | 2025 |
| Cultitude Limited | Professional & scientific | 2025 |
| Curry Garden Takeaway Ltd | Hospitality | 2016 |
| Curry Southsea Limited | Hospitality | 2023 |
| CWK Electrical Limited | Construction | 2002 |
| Cycle-Works Limited | Manufacturing | 1996 |
| Cydney Terrace Limited | Real estate | 2017 |
| Cyoung Limited | Hospitality | 2024 |
| D & H Carpentry and Construction Ltd | Manufacturing | 2018 |
| D & S Bowers Groundworks Ltd | Construction | 2013 |
| D C 2 Light Networks Ltd | Information & communication | 2001 |
| D L Home Improvements Ltd | Construction | 2025 |
| D OD Control Engineering Limited | Professional & scientific | 2013 |
| D R K Interiors Ltd | Construction | 2013 |
| D Robinson Brickwork Ltd | Construction | 2025 |
| D T Developments (Southern) Limited | Construction | 2015 |
| D Top Store Limited | Wholesale & retail | 2025 |
| D W L Home Improvements Ltd | Construction | 2021 |
| D&H Damp Proofing Ltd | Construction | 2025 |
| D'Luxe Nails Ltd | Other services | 2026 |
| D.A.T Utilities Ltd | Construction | 2019 |
| D.Gerocs Ltd | Construction | 2019 |
| D3 Marketing Ltd | Professional & scientific | 2006 |
| D4U Couriers Ltd | Transport & logistics | 2025 |
| Daish & Son's Builders Ltd | Construction | 2015 |
| DAL Enterprise Limited | Hospitality | 2024 |
| Dalit Store Ltd | Wholesale & retail | 2025 |
| Dalo Property Limited | Real estate | 2020 |
| DAN Lacey Ltd | Information & communication | 2015 |
| Danu Consulting Ltd | Administrative & support | 2026 |