| Roche Lettings Limited | Real estate | 2021 |
| Rock Rose Properties Ltd | Real estate | 2025 |
| Rockpool Kayaks Ltd | Manufacturing | 2005 |
| Rocky’S Gym Limited | Arts & recreation | 2026 |
| Roots and Stars Forest School Ltd | Education | 2023 |
| Rosehill Caravan Sales & Sites Limited | Hospitality | 1962 |
| Roundhouse Resorts Ltd | Hospitality | 2024 |
| RP Construction & Rendering Ltd | Construction | 2025 |
| RRA Group Ltd | Wholesale & retail | 2026 |
| Russell GAS Services Ltd | Construction | 2018 |
| Rusty's to Go Ltd | Hospitality | 2026 |
| Ryder Construction Ltd | Construction | 2025 |
| SA Investment Homes Ltd | Real estate | 2026 |
| Satinheath Limited | Arts & recreation | 1993 |
| Scbr Construction Limited | Construction | 2014 |
| Schulze Property Limited | Real estate | 2002 |
| Science & Engineering Applications Ltd | Information & communication | 2018 |
| Sea Breeze Fisheries Limited | Hospitality | 1991 |
| Sea Port Hotel Ltd | Hospitality | 2021 |
| Sea Shanty Restaurants Limited | Hospitality | 2012 |
| Seaview Developments (Anglesey) Limited | Construction | 2006 |
| Sebastian Mills Limited | Construction | 2016 |
| Security Giant Ltd | Wholesale & retail | 2017 |
| Shahzad Seraj Limited | Wholesale & retail | 2025 |
| Simply Street Ltd | Hospitality | 2020 |
| SJA Group Ltd | Households | 2025 |
| SKL Bathrooms Limited | Construction | 2024 |
| SKL Plumbing & Heating Limited | Construction | 2023 |
| SKL Property Group Ltd | Real estate | 2025 |
| SKL Vending Group Limited | Real estate | 2025 |
| SLD Pproperty CYF | Real estate | 2024 |
| SM Properties Investor Ltd | Real estate | 2024 |
| Soft Play Llangefni Ltd | Arts & recreation | 2025 |
| Sophie’S Cleaning Services Ltd | Administrative & support | 2025 |
| Space Like This Ltd | Wholesale & retail | 2013 |
| Spidershop Limited | Information & communication | 1999 |
| Stable Minds Your Safe Space Wales CIC | Health & social care | 2024 |
| Stad Cefn Tarw Services Limited | Households | 2020 |
| Stagewell Industries Ltd | Administrative & support | 2013 |
| Stan's Choice Limited | Manufacturing | 2022 |
| Straits Line Limited | Professional & scientific | 2018 |
| Stuart Marine Limited | Other services | 2018 |
| Sunsize Limited | Hospitality | 2018 |
| Sutton Mann Limited | Wholesale & retail | 2024 |
| Swallows Nest Ltd | Hospitality | 2020 |
| Sweets and Occasions Ltd | Wholesale & retail | 2023 |
| Swish Coaching Limited | Arts & recreation | 2024 |
| Sylfaen Associates Ltd | Professional & scientific | 2010 |
| T BAE Limited | Arts & recreation | 2020 |
| T R Jones & Sons Limited | Wholesale & retail | 2007 |
| T.H.T. Homes Ltd | Real estate | 2024 |
| Tafarn Cybi Ltd | Hospitality | 2025 |
| TAI Swtan CYF. | Construction | 2018 |
| Tara Martin Dental Care Limited | Health & social care | 2018 |
| Team Maro Ltd | Professional & scientific | 2023 |
| Terry D Hughes Ltd | Manufacturing | 2020 |
| That Burger GUY Ltd | Hospitality | 2023 |
| THE Beach Motel Limited | Hospitality | 2005 |
| THE Black Seal Restaurant Ltd | Hospitality | 2015 |
| THE Branch Holyhead Ltd | Hospitality | 2020 |
| THE Branch Public House Limited | Hospitality | 2026 |
| THE Campus App Ltd | Information & communication | 2024 |
| THE Island Edit Ltd | Information & communication | 2025 |
| THE Lobster POT Anglesey Limited | Wholesale & retail | 2014 |
| THE Old Boathouse Ltd | Hospitality | 2025 |
| THE Vault HH Ltd | Hospitality | 2026 |
| Thorne Maritime Solutions Ltd | Transport & logistics | 2018 |
| Three Brothers 2018 Ltd | Wholesale & retail | 2018 |
| Ticklock Limited | Hospitality | 1986 |
| Tildesley Environmental Services Limited | Professional & scientific | 2019 |
| Tinpot Holdings Ltd | Hospitality | 2024 |
| Tinyegg Limited | Information & communication | 2012 |
| TIR Dafarn Limited | Agriculture & fishing | 2020 |
| TM Appliance Repairs Ltd | Other services | 2021 |
| Tone Lifestyle Ltd | Wholesale & retail | 2023 |
| Top G Store Ltd | Other services | 2026 |
| Tour MON Anglesey Tours Limited | Administrative & support | 2025 |
| Towergate Properties Ltd | Real estate | 2013 |
| Towyn Capel Residential Home Ltd | Health & social care | 2026 |
| Trade Security Supplies Limited | Manufacturing | 2018 |
| Transfreight Services Limited | Transport & logistics | 1998 |
| Trearddur Holiday Bungalows LLP | | 2024 |
| Trearddur Mews Management Company Ltd | Households | 2024 |
| Treatment Wetlands Ltd | Water & waste | 2019 |
| Trefonen House Limited | Hospitality | 2018 |
| True North Surveying Ltd | Construction | 2022 |
| Turnkey Housing Ltd | Real estate | 2025 |
| TY Cochyn Ltd | Hospitality | 2025 |
| TY Taclus Anglesey Ltd | Administrative & support | 2026 |
| Tycoon London Ltd | Wholesale & retail | 2017 |
| TŶ Rhost Ltd | Hospitality | 2024 |
| UK Broker One Limited | Professional & scientific | 2024 |
| Ultra Prime Limited | Wholesale & retail | 2024 |
| Umbrella Payroll Solutions Ltd | Professional & scientific | 2020 |
| Unique-Kids (MON) Ltd | Manufacturing | 2014 |
| Untaptd Ltd | Professional & scientific | 2020 |
| Valley Equestrian Centre Limited | Hospitality | 2002 |
| Valley Pizza Ltd | Hospitality | 2021 |
| Van Life Anglesey Ltd | Wholesale & retail | 2020 |
| Veda Wellbeing Limited | Other services | 2019 |