In addition to the statutory due dates listed above, estimated tax payments also have their own due date schedule. Often, taxpayers are confused on the due dates for estimated tax payments since they do not fall on a typical quarter end. The first quarter estimated tax payment is due the same time as the prior year’s tax or extension payment is due. The fourth quarter payment is due in the year following the tax year. This is practically the only time a payment made in a following year impacts the prior year tax return for cash basis taxpayers.