A tax penalty will happen on unpaid property tax. It occurs mostly at the county level in the United States. A penalty may also happen to income taxes and other taxes, depending on the type of tax. The penalty may be a percentage. In general, it is a percentage of what is owed, charged once the payment is 30 to 60 days overdue. The issuing organization is legally required to state when a tax penalty will happen on the nonpaid tax debt. The organization may also be required to list the percentage amount of the penalty at the time that the debt invoices and is due. Nonpayment of tax debt may lead to costly penalties as well as interest, depending on the laws of the region. To fight such payments, or to reduce them, it is best for an individual or business to use the services of an attorney.