Information quality deficiencies have been detected in occupational safety and health surveys in Europe, which typically gather self-reported data responded by employers or their representatives. For instance, their low response rates and informant profiles make estimations on establishments with safety representatives (SRs) unreliable. We tested the mode of administration and informants as sources of error regarding establishments with SRs in Catalonia, Spain. Two sources of information were compared: the Second Catalan Survey of Working Conditions 2011 (IICSWC)—with a methodology similar to surveys conducted at the state and European level—and the Progam on Prevention of Risks Management in Companies (PPRMC)—in which the labor authority collected data using a documentary verification in another sample of establishments. Percentage of establishments with SRs was estimated using the data from the PPRMC and also the differences in percentage between sources and informant profiles (with 95 percent confidence interval). Results show that the IICSWC overestimates the percentage of establishments with SRs.