Sales Tax Payable is affected by your prior payments, if the amount was higher or lower than the amount owed at that point in time. That is just a Running Balance, in other words.
You owe $1,000 for Jan and pay it. Then, you issue a Credit Memo or otherwise Change something in Jan. Now Feb is going to reflect that difference that happened because of changes in Jan.
Perhaps the "audit" you are asking about is the Audit Trail report. Run it on Sales transactions, dated in the prior month, for changes Entered/Modified after the end of that month. This reveals where someone made changes to your historic data = making a mess of the prior sales data, affecting Sales and Sales Taxes.