Tax Reports Incorrect

Hi All

Our Tax Reports are giving incorrect information.  :eek:

I run the standard GST on Sales Summary and then compare the Net Amount and Tax Amount to the actual invoices and on certain invoices the tax amount on the GST report is incorrect. 

Example[INDENT]Invoice #26 Gross Amount = $220.00 but
GST Report states invoice #26 as Net Amt=$200.00  Tax Amt=$19.00
Drill down to invoice #26 and the Net Amt=$200.00 Tax Amt=$20.00[/INDENT]

Every line on the invoice has 10% GST so there is no GST Free lines that normally would cause the difference between Net and Tax amounts. 

I am going to log with Netsuite, but I thought I would post here first, mainly because the error is only on some invoices, so the problem may not be with Netsuite, but with how something is, or isn't set up correctly in our account, and perhaps someone else has posted a thread and the problem has been discussed and sorted.