The Taxable/Exempt Sales report has the option to be run on accrual basis or cash basis. If you select cash basis in the report's options it will report on invoices paid in the selected time frame instead of invoices dated in that time frame. That should solve your problem.

I need it for our receivables.  Indiana allows us to not pay the sales tax until we are paid.  So exporting the A/R report into Excel then going through each invoice to find out how much tax was invoiced is a pain.  Just trying to find an easier way.

That's exactly the purpose of the cash basis option on the Taxable/Exempt Sales report. Instead of going through your receivables to see what has not been paid, just run the Taxable/Exempt Sales report and select the Cash Basis option. It will give you are report showing sales and tax collected based on invoices that were paid that month regardless of the invoice date. Invoices that have not been paid will be excluded from the report.