Checking people’s writing for correctness is one of the prominent language technology applications. In the Czech language, punctuation errors and mistakes in subject-predicate agreement belong to the most severe and most frequent errors people make, as there are complex and non-intuitive rules for both of these phenomena. At the same time, they include numerous syntactic, semantic and pragmatic aspects which makes them very difficult to be formalized for automatic checking. In this paper, we present an automatic method for fixing errors in commas and subject-predicate agreement, using pattern-matching rule-based syntactic analysis provided by the SET parsing system. We explain the method and present first evaluation of the overall accuracy.