Our client started their LLC in 2014 and started operations in 2015. They elected to file their taxes as an S Corporation. They didn't file any payroll taxes for 2015 and 2016. They came to our office in 2017 and have now paid all their back payroll taxes including penalties. We want to request IRS to refund them the payroll tax penalties incurred in 2015 and 2016 on the basis of First Time Abatement since they were new, first time business owners.

Are there any tips on how to form the request letter to IRS and what to write in it to increase the chances of IRS refunding the penalties? Has anyone had any experience with this?