Internal and external factors influence teachers' daily assessment decisions. The purposes of teachers' assessments are crucial, as these purposes guide the assessment process. Still, little is known about teachers' assessment purposes. The aim of this study is to identify and describe the different purposes of assessments that Civics teachers describe. Thirteen Civics teachers in Swedish upper secondary school were interviewed about their assessment practices. A thematic analysis generated four main themes about teachers' purposes: enacting policy, improving learning, pulling for students and handling administration. There are tensions between different purposes, and teachers need to balance these in their assessment decisions and when validating. Specific Civics subject matter also influences purposes and tensions. This study contributes to the understanding of the influence of internal and external factors on teachers' assessment practices in Civics, and to the understanding of the complexity of validity with multiple purposes in the school context.