I'm in PA and we're required to charge Sales Tax for administrative services. I'd like to move my client over to a retainer agreement but I'm wondering how you would add in the sales tax? I'm assuming that I would just take the retainer fee and add the % of sales tax to the total. I didn't know if I should just assume sales tax is included in the retainer fee and be sure that I'm charging enough to cover the tax.

I think I just answered my question but I'd still love to know how others handle it.