The paper describes CzeSL, a learner corpus of Czech, together with basic properties of its design. It starts with a brief introduction of the project within the context of AKCES, a programme addressing Czech acquisition corpora; in connection with the programme we are also concerned with groups of respondents, including differencies due to their L1; further we comment on the choice of sociocultural metadata recorded with each text and related both to the learner and the text production task. Next we describe the intended uses of CzeSL. The main parts of the text deal with transcription and annotation. We explain the issues involved in transcrition of the handwritten texts and present the concept of a multi-level annotation scheme including taxonomy of captured errors. We conclude by mentioning results from an evaluation of the error annotation and presenting plans for future research.