If any tax collector or tax commissioner fails to settle his accounts with the commissioner as provided by law, the commissioner shall issue execution against the tax collector or tax commissioner and his sureties for the principal amount, together with interest at the rate of 20 percent per annum on the amount. If upon a final settlement it appears that the tax collector or tax commissioner was entitled to credits at the time he is required by law to settle, the commissioner may allow the credits and charge interest only on the amount for which the tax collector or tax commissioner is in default, together with all the costs and attorney's fees incurred by reason of the issuance of the execution.