Abstract—In this paper, a low complexity algorithm for the design of a time-varying correction filter of finite impulse response (FIR) type is presented. Using the obtained filter design to correct a preceding time-varying system, a correction performance in the least-squares sense can be ensured. The adaptation of the filter design requires a moderate computational complexity and is suitable for real-time applications. Thus, a correction of nonperiodically time-varying systems can be achieved where design methods, which rely on computationally intensive operations, e.g. numerical integration, can not be applied. At the same time, its application is not limited to weakly time-varying systems as iterative solutions are, which can correct for weakly time-varying behavior by gradually reducing the induced signal error over multiple stages.