Re-filing of corrected ST-3
Before the deadline:
Any return for the same taxpayer and period that is submitted will REPLACE the previously filed return as long as all of this happens prior to the filing deadline. The most recently filed return will supersede any previously filed return.
The payment, however, is a different matter. You MUST delete the incorrect payment in the system at the GTC. Otherwise, the payments will simply accumulate and will ALL be processed on the payment date if they are left in the system at the GTC.
After the deadline:
If the error is only caught after the 20th, the incorrect return would have been processed and the payment would have already been made. In this case, the proper action for the user is to file an AMENDED return (this is on the Returns menu in the sales tax module). You should NOT include payment with an Amended Return but rather wait until the return has been processed by the GTC and then check the account of the taxpayer to see whether the GTC has calculated the balance due (sometimes a credit amount).
If you agree with the amount remaining to be paid, you should pay that amount promptly. In the case of a credit balance, GTC policy is for the users to request a refund from the menu on the GTC site. (note: we advise users, if the taxpayer agrees, to wait until the next filing and simply reduce their payment amount on the next filing so that the credit is applied and the balance returned to zero. While this is NOT GTC policy, this method also works without complaints or problems.)