The τ leptons theory and experimental data: Monte Carlo, fits, software and systematic errors

Status of τ lepton decay Monte Carlo generator TAUOLA is reviewed. Recent efforts on development of new hadronic currents are presented. Multitude new channels for anomalous τ decay modes and parameterization based on defaults used by BaBar collaboration are introduced. Also parameterization based on theoretical considerations are presented as an alternative. Lesson from comparison and fits to the BaBar and Belle data is recalled. It was found that as in the past, in particular at a time of comparisons with CLEO and ALEPH data, proper fitting, to as detailed as possible representation of the experimental data, is essential for appropriate developments of models of τ decays.In the later part of the presentation, use of the TAUOLA program for phenomenology of W, Z, H decays at LHC is adressed. Some new results, relevant for QED bremsstrahlung in such decays are presented as well.