You need to trace the transaction backwards.  How did you overpay the Sales Tax?  Did you collect more than you needed to from customers?  If so, then you have a liability to refund their overpayments and you would post the refund from the state to a Liability account.

If the amount collected from customers is correct, then where did the original payment of the sales tax get recorded?  If your predecessor simply paid more than was owed, then the balance in your Sales Tax Liability account is probably too low and you need to apply the refund from the state there.  

Or was it a Use Tax payment, which would have been recorded as an expense?  Then you would post the refund from the state to whatever account(s) hold the overcharge on the expenses.

Hope this helps!