| C Ryan Properties Ltd | Real estate | 2017 |
| Caban Kingsland Ltd | Health & social care | 2014 |
| CAE Pwll Limited | Hospitality | 2021 |
| Caffi MON Bistro CYF | Hospitality | 2024 |
| Cambria Enterprises Ltd | Other services | 2017 |
| Canfod Cymru CIC | Education | 2018 |
| Canolfan Cynghori Ynys MON Citizens Advice Bureau | Information & communication | 1998 |
| Canvas Stores Ltd | Wholesale & retail | 2026 |
| Captive & Field Herpetology Ltd | Professional & scientific | 2020 |
| Carlton Blinds (Cymru) Limited | Manufacturing | 2004 |
| Carreg Y Fran Ltd | Hospitality | 2025 |
| Carregwyllt | Hospitality | 2021 |
| Cartrefi Cymry CYF | Real estate | 2024 |
| Casa Organics Ltd | Wholesale & retail | 2019 |
| Catch 22 Brasserie Limited | Hospitality | 2015 |
| Caws MÔN Limited | Manufacturing | 2023 |
| CDM Safety Management Consultants Ltd | Professional & scientific | 2023 |
| Cedar ADS Ltd | Professional & scientific | 2002 |
| Celtic Spirit Co. (Anglesey) Limited | Manufacturing | 2019 |
| Cempatica Advisory Limited | Professional & scientific | 2026 |
| Central Garage (Bryngwran) Limited | Wholesale & retail | 2014 |
| Charcuterie MON Ltd | Manufacturing | 2023 |
| Charlie Straw Ltd | Professional & scientific | 2022 |
| Chazzmarelda Enterprises Ltd | Administrative & support | 2023 |
| Chemregs (UK) Ltd | Professional & scientific | 2004 |
| Chickenzown Ltd | Information & communication | 2025 |
| Chong Asset Holdings Ltd | Real estate | 2024 |
| Church Bay Investments Limited | Real estate | 1982 |
| Church Bay Ltd | Transport & logistics | 2012 |
| Cladcheck Associates Limited | Construction | 2013 |
| Clean Design UK Nova C.I.C. | Information & communication | 2024 |
| Clear View Contract Window Cleaning Ltd | Administrative & support | 2017 |
| CM Gastrocare Limited | Health & social care | 2024 |
| Cnon Offshore Limited | Transport & logistics | 2018 |
| Coast Construction Ynys MON Limited | Construction | 2020 |
| Cobiatec Limited | Professional & scientific | 2000 |
| Coco Lane Creative Ltd | Information & communication | 2025 |
| Colin Roberts JCB Hire Limited | Construction | 2014 |
| Condessa Limited | Manufacturing | 2019 |
| Conveyor Collective CIC | Information & communication | 2025 |
| County Tile Centre Limited | Wholesale & retail | 2004 |
| CPM Marine Ltd | Professional & scientific | 2016 |
| Croeso Lettings Ltd | Real estate | 2025 |
| CRS Roofing Services Ltd | Construction | 2026 |
| Crystal Clear Window Cleaning Services Ltd | Administrative & support | 2025 |
| Cuffed-In Coffee Ltd | Hospitality | 2019 |
| Cuffed-In Coffee Roasters Ltd | Hospitality | 2022 |
| Curlew Blue Ltd | Real estate | 2023 |
| Cw-Aviation Ltd | Manufacturing | 2025 |
| Cwrw Cybi Ltd | Wholesale & retail | 2024 |
| Cybi Business Forum CIC | Administrative & support | 2025 |
| Cyfeillion Swtan | Arts & recreation | 1998 |
| Cymell Limited | Health & social care | 2013 |
| Cymunedau'N Ymlaen MÔN Communities Forward | Administrative & support | 2012 |
| Cymyran Constrution Company Limited | Wholesale & retail | 2009 |
| Cynnal IT and Recycling C.I.C. | Other services | 2024 |
| Cynnal IT Limited | Information & communication | 2022 |
| D C Hipwood Transport Limited | Transport & logistics | 2014 |
| D Griffiths Plumbing & Heating Limited | Construction | 2025 |
| D Wooley Upvc Windows Ltd | Construction | 2024 |
| Dairy Ventures Ltd | Financial services | 2022 |
| Dandelionwellness Limited | Arts & recreation | 2023 |
| Danielle LEE Ltd | Professional & scientific | 2023 |
| David North Construction Ltd | Construction | 2022 |
| DAVID.WALKER.B2 Limited | Manufacturing | 2024 |
| DEE Seafoods Limited | Agriculture & fishing | 2017 |
| Deepdock Limited | Agriculture & fishing | 1987 |
| Detail BUG Car Care Ltd | Wholesale & retail | 2017 |
| Dewi Roberts Plumbing & Heating Ltd | Construction | 2024 |
| Digartref CYF. | Health & social care | 1998 |
| Dock Bars Ltd | Hospitality | 2025 |
| DOM Mahon Property Ltd | Real estate | 2021 |
| Dotty Braille Ltd | Professional & scientific | 2026 |
| Dragon Developments (Anglesey) Limited | Real estate | 2023 |
| Dragon Wind Energy (Anglesey) Limited | Energy | 2015 |
| Draig Goch Limited | Construction | 2017 |
| DWR Y Wyddfa Limited | Water & waste | 2003 |
| Dwrigging Ltd | Construction | 2025 |
| E & SF Williams Properties Limited | Real estate | 2021 |
| E-Juice Couture Limited | Wholesale & retail | 2019 |
| Edward Construction Services Ltd | Construction | 2001 |
| Eifions Coaches Ltd | Transport & logistics | 2007 |
| Eirianallt Limited | Agriculture & fishing | 2011 |
| Elmstead Market Ltd | Wholesale & retail | 2026 |
| Embassy Associates Ltd | Hospitality | 2003 |
| Embroidery OR Print Ltd | Manufacturing | 2024 |
| Emlyn Enginering Ltd | Professional & scientific | 2025 |
| Emyr Roberts Electrical & Renewables Ltd | Construction | 2023 |
| EPC Energy Services Ltd | Extraterritorial | 2022 |
| EPK Holdings Limited | Administrative & support | 2018 |
| Estate and Will Planners Ltd | Other services | 2023 |
| EVA Barbershop Ltd | Other services | 2025 |
| Evans & Moose Ltd | Other services | 2020 |
| Everyday Abode Ltd | Wholesale & retail | 2025 |
| Fasthousemoves Ltd | Transport & logistics | 2025 |
| Feral Collective Limited | Wholesale & retail | 2025 |
| Ffrwyth Y MÔR (MÔN) CYF | Wholesale & retail | 2018 |
| Fibonacci Geological Limited | Professional & scientific | 2014 |
| Fiscal Clarity Anglesey Ltd | Professional & scientific | 2024 |
| Foxwells Garden Ltd | Information & communication | 2021 |