By customer
- Cabela’s
- Cabin Attendants Union
- CACEIS
- Caixa Economica Federal
- Caja de Compensación Familiar (CAFAM)
- Calendars.com
- Calgary Catholic School District (CCSD)
- California Natural Products
- Callico Distributors
- Calzessa International
- Camden Council
- Camelot
- Cameron
- Campbell Brothers
- Canada Health Infoway
- Canadian Clothing Chain
- Canadian Natural Resources Ltd
- Canadian Provincial Health Systems
- Canderel
- Canucks Sports & Entertainment
- Capgemini Canada
- Capital District Physicians Health Plan (CDPHP)
- Capri S.r.l
- Cardiff and Vale University Health Board
- Career Education Corporation
- CareMedic Systems Inc.
- Carleton University
- Carphone Warehouse
- Cars.com
- Carter's
- Casa Oliveira
- Case Western Reserve University, Case School of Engineering
- Castilla y León
- Castorama
- Catalina Marketing
- Catnic
- Cbeyond
- CBP
- CCLV
- CECA (Spanish Confederation of Savings Banks)
- Cegedim Activ
- Celina Insurance Group
- Cellular South
- Cengage Learning Inc.
- CenterBeam
- Center for Research in Water Resources at the University of Texas at Austin
- Centerstone Research Institute
- Central Department for Water and Environment
- Central Depository Company of Pakistan Limited (CDC)
- Central Iowa Power Cooperative
- Centrax
- Centre for Railway Information Systems
- Centre Hospitalier de la Polynésie Française
- Centre Hospitalier de Niort
- Centre of Excellence for Applied Research & Training (CERT)
- Cetelem
- Cetip
- CEWE COLOR AG & Co. OHG
- CEZ Group
- Chandra Asri
- Chantal Sellier Consulting
- C.H. Briggs
- Checkers Drive-In Restaurants
- Chemring
- Cheshire County Council
- Chichester School District
- Chickasaw Nation Division of Commerce
- Chilean Red Cross (Cruz Roja Chilena)
- Chilean Red Cross
- China Merchants Bank New York branch
- China New Media Development Zone
- China Ocean Shipping (Group) Company - COSCO
- China Railway Materials Commercial Corporation
- China Telecom Corporation Jiangxi
- Chinese Insurance Company (CIC)
