Joining Late in a month - if an employee joins on 28-Jan-2020 then it might be too late to include him in the payroll for the month since the payroll processing might have already started or finished. In such a scenario the first payroll month can be set at Feb-2020 and the number of days in Feb can be made as 32 (28+4). Please refer to the article on Employee details - payroll details for more information.
If for some reason an employee is added to the system with a date of joining
in past. For example, if employee date of joining is 1-Oct-2019 and today is
15-Feb-2020 and payroll for all employees has been run till Jan-2020 then you
can select Feb-2020 as the first payroll month for this employee. The data for
Oct-2019 to Jan-2020 can be calculated outside the system and uploaded using Year to Date upload.
But the compliances like TDS / PF / ESI and 24Q for this period will have to
managed outside the system. Once YTD data is uploaded the 24Q for Quarter 4 will
be generated accurately.