Payroll is entered using a voucher system. Most of the time the payroll vouchers are generated by a payroll calculation program. However, there are times when the computer breaks down when the payroll needs to be run (when else?). In this case, payroll has to be calculated and paid manually. When the computer is running again, the manual payroll can be entered and "paid".
There are times when the need arises to make adjustments to a current payroll run. This might be needed for bonuses, special one time deductions, etc.