When you process payroll tax forms for a particular tax period, QuickBooks
this date to determine the amount of tax you have paid. This date also affects
liability balances report.
When you create a liability payment, QuickBooks takes the dates you
specified on the Pay Liabilities window (in the Show Payroll Liabilities
fields) and puts them in this field.
If there is no date, enter the ending date for the tax period in which you
owed this payment. For example, if you are entering a tax payment you made on
October 10 for tax you owed as of September 30, enter 9/30 (and the year).