Chipping in my 2c worth, I really would advise against trying to go into Payroll. One of the biggest things I say to clients is, you don't mess with Payroll. We're very cautious when running updates, backing up at every step etc, getting them to test afterwards.
Even the big providers get the calculations wrong. Leave balances, earning time off, crediting time worked on holidays, adjusting leave to salaries and how it affects balances, every country has different regulations etc etc… All that ties into the company balances (leave is a liability etc)