We discuss a retrieval model in which the task is to complete a sentence, given an initial fragment, and given an application specific document collection. This model is motivated by administrative and call center environments, in which users have to write documents with a certain repetitiveness. We formulate the problem setting and discuss appropriate performance metrics. We present an index-based retrieval algorithm and a cluster-based approach, and evaluate our algorithms using collections of emails that have been written by two distinct service centers. Categories and Subject Descriptors H.3.3 [Information search and retrieval]: Retrieval models; H.5.2 [User interfaces]: Natural language General Terms Algorithms, Experimentation Keywords Retrieval models, indexing methods, applications