Using transactions in Java Card bytecode programs can be rather tricky and requires special attention from the programmer in order to work around some of the limitations imposed and to avoid introducing serious run-time errors due to inappropriate use of transactions.In this paper we present a novel analysis that combines control and data flow analysis with an analysis that tracks active transactions in a Java Card bytecode program. We formally prove the correctness of the analysis and show how it can be used to solve the above problem of guaranteeing that transactions in a Java Card bytecode program are well-formed and thus do not give rise to run-time errors.