A computer-implemented method of calculating tax liability using automatically generated estimates uses a computing device connecting to a shared data store configured to store user-specific tax data therein. The computing device executes an estimation module configured to estimate user-specific tax data and write the estimated user-specific tax data to the shared data store. A tax calculation engine configured to read user-specific tax data from the shared data store and write calculated tax data to the shared data store is executed, wherein at least some of the read data comprises estimated user-specific tax data.