Calendar days and payable days are vital information to arrive at current earnings. The HR department will either share payable days or loss of pay (LOP) days to Payroll Processor, month on month.
The sum of all applicable compensation components, prorated for the payroll period, represents the earnings such as Basic, HRA, Conveyance, Medical Allowance, and Special Allowance. For employees with full payable days, this will be full earnings and for the rest, prorated earnings.
For example, take the case of an employee who joined on 7th January 2013. Here, payable days will be 25.
In addition to this, one-time payouts can also come as part of the earnings. For Payroll Processor, collecting inputs on one-time payouts (ad hoc earning) from HR is a checklist item every month. Examples of one-time payouts are Joining Bonus, Attendance Bonus, and Overtime Pay, etc.