noun
delinquent tax; overdue tax; tax in arrears
A legal/financial term for tax that is past due and unpaid. Often used in official contexts such as tax notices.
延滞税が発生しないように、期限内に納税してください。
Please pay your taxes by the due date to avoid delinquent tax charges.
滞納 is the act of falling behind on payments (tax, rent, etc.), while 延滞税 is the specific tax amount that is overdue.
Compound of 延滞 (delinquency, arrears) and 税 (tax).