| Cinnamon by Abdi Ltd. | Manufacturing | 2025 |
| Cinnamon Collection Limited | Hospitality | 2016 |
| Cinnamon Group (UK) Limited | Construction | 2007 |
| Cinnamon Hill Care Services Ltd | Health & social care | 2024 |
| Cinoci Limited | Manufacturing | 2024 |
| Cinzeen Property Holdings Ltd | Real estate | 2026 |
| Cipher Arts Limited | Information & communication | 2000 |
| Ciphonika Ltd | Professional & scientific | 2026 |
| Ciplato AI Limited | Information & communication | 2024 |
| Ciprysa Transport Ltd | Transport & logistics | 2024 |
| Ciragan Palace Ltd | Real estate | 2024 |
| Circadian Housing Ltd | Real estate | 2024 |
| Circavivendi Limited | Wholesale & retail | 2019 |
| Circle Accounting Services Limited | Professional & scientific | 2011 |
| Circle Centrix Limited | Information & communication | 2026 |
| Circle Media Online Ltd | Professional & scientific | 2020 |
| Circle of Life Events Ltd | Education | 2022 |
| Circuare Limited | Information & communication | 2020 |
| Circuit & Clay CIC | Professional & scientific | 2024 |
| Circuit Services Limited | Construction | 2002 |
| Circuit Tyres Limited | Administrative & support | 2005 |
| Circular Living Limited | Real estate | 2025 |
| Circular Search Limited | Administrative & support | 2021 |
| Circularconnex Sourcing Consultancy Ltd | Professional & scientific | 2025 |
| Circulus Energy Limited | Water & waste | 2020 |
| Circulus Group Limited | Financial services | 2021 |
| Circulus Holdco Limited | Financial services | 2020 |
| Circulus Workspace Ltd | Administrative & support | 2021 |
| Circus Media Holdings Ltd | Administrative & support | 2012 |
| Circus Records Artist & Employee Scheme Ltd | Information & communication | 2024 |
| Circus Records Ltd | Arts & recreation | 2010 |
| Circusmash Ltd | Education | 2014 |
| Cirex Ltd | Construction | 2021 |
| CIRKULARIS8 Limited | Administrative & support | 2017 |
| Cirrostratus Exedra Ltd | Information & communication | 2018 |
| Cirrus Environmental and Planning Consultancy Limited | Professional & scientific | 2011 |
| Cirrus Well Limited | Wholesale & retail | 2020 |
| Cirs Consulting UK Ltd. | Administrative & support | 2023 |
| Cirstoiu Ltd | Manufacturing | 2025 |
| CIS Done Ltd | Professional & scientific | 2023 |
| CIS Eco Group Limited | Construction | 2025 |
| CIS Infrastructure Specialists Ltd | Construction | 2018 |
| Ciscal Tech Ltd | Information & communication | 2024 |
| Ciscom (U.K) Limited | Information & communication | 2015 |
| Cisnade Ltd | Transport & logistics | 2025 |
| Cisutton Ltd | Hospitality | 2020 |
| CIT Events Ltd | Administrative & support | 2019 |
| CIT Realisations Limited | Water & waste | 1974 |
| Cit-E Group Ltd | Financial services | 2022 |
| Cit-E Group UK Ltd | Extraterritorial | 2015 |
| Citadel Apartments Limited | Hospitality | 2015 |
| Citadel Fire Safety Ltd | Professional & scientific | 2023 |
| Citadel Homes Ltd | Real estate | 2024 |
| Citadel Housing Solutions Limited | Real estate | 2025 |
| Citadel Immigration Lawyers Ltd | Professional & scientific | 2014 |
| Citadel Music Group Limited | Hospitality | 2017 |
| Citi Accountants Ltd | Professional & scientific | 2016 |
| Citi on the Hill Properties Ltd | Real estate | 2019 |
| Cities Group Holdings Limited | Financial services | 2014 |
| Cities UK Limited | Financial services | 2004 |
| Citigate Consulting Limited | Information & communication | 2011 |
| Citivision Ltd | Real estate | 2022 |
| Citizen Business Services Limited | Professional & scientific | 2004 |
| Citizen Click CIC | Information & communication | 2021 |
| Citizen Coaching C.I.C. | Administrative & support | 2005 |
| Citizen Health Limited | Health & social care | 2017 |
| Citizen Home Ltd | Wholesale & retail | 2017 |
| Citizen Hub CIC | Professional & scientific | 2026 |
| Citizen Lawyer Ltd | Information & communication | 2022 |
| Citizen New Homes Limited | Construction | 2011 |
| Citizen Property Investment Ltd | Real estate | 2022 |
| Citizen Support Ltd | Hospitality | 2026 |
| Citizen Treasury 2 PLC | Financial services | 2012 |
| Citizen Treasury PLC | Financial services | 2017 |
| Citizen Treasury Vehicle Limited | Financial services | 2017 |
| Citizen Vault Ltd | Information & communication | 2025 |
| Citizens Advice Solihull Borough | Other services | 2011 |
| Citizens Midlands Housing & Support Ltd | Real estate | 2020 |
| Citizens' Gavel U.K GTE Ltd | Information & communication | 2021 |
| Citrine Arts CIC | Arts & recreation | 2025 |
| Citrine Network Limited | Professional & scientific | 2010 |
| Citrine Property Limited | Real estate | 2022 |
| Citrus Developments Limited | Professional & scientific | 2010 |
| Citrus Facilities Services GRP Limited | Administrative & support | 2018 |
| Citrus Studio Limited | Real estate | 2022 |
| Citrus Talent Digital Ltd | Professional & scientific | 2023 |
| Citrussoft Ltd | Information & communication | 2023 |
| Citrusyellow Ltd | Professional & scientific | 2009 |
| Cituslink Technology Solutions Ltd | Information & communication | 2025 |
| City & Countryside Electrical Engineering Services Ltd. | Construction | 2023 |
| City 505 Limited | Real estate | 2019 |
| City Academic Centre Ltd | Information & communication | 2022 |
| City Accident Management Ltd | Financial services | 2009 |
| City Aluminium Ltd | Manufacturing | 2024 |
| City and Associates Project Consultants Limited | Information & communication | 2014 |
| City Auto Centre Ltd | Wholesale & retail | 2006 |
| City Car Care Limited | Wholesale & retail | 2009 |
| City Car Parts Ltd | Wholesale & retail | 2023 |
| City Care Housing Ltd | Real estate | 2025 |
| City Carpets & Beds Ltd | Wholesale & retail | 2019 |