Refusals are a considerable source of non-response in surveys. During the field period, some surveys collect reasons for refusals as survey Para-data. In addition to providing information for research these data can also provide information about non-respondents that can be used to reduce refusal rates. However, there is a lack of standardized instruments of data collection, the fact of which declines reliability, validity, and objectivity of the data collected. This article presents a standardized instrument - a categorization scheme - for classifying reasons for refusals. The instrument was developed using content analysis of open-ended comments by interviewers in the German General Social Survey (ALLBUS 2008). The interrater-reliability of the developed categorization scheme is .84 and thus satisfying. We give some suggestions on how the categorization scheme can be used by surveyors as well as by interviewers when collecting reasons for refusals.