Call ADP and discuss it with them (not customer service but an actual sales person IN PERSON) before you do anything else. They rule the payroll world and likely have a solution for you. Why write one from scratch?! Anyway, you’ve got other issues here than only payroll. You need reliable withholding, employee advice, HR protection, etc. Having a company like ADP in your court is worth the nominal fee they charge for running your checks every cycle. They turned out to be golden for us on several occasions.