Supplementary payroll process

Hi,
I wanted to know about supplementary payroll process, why do we need to run this process what are the prerequisites to run this process. Any metalink note or docs. or link if you ppl can suggest me i shall be very thank full to you gurus and others further more in order to design a generic user front end screen and table structure what thing that i must keep in mind in order to build customize solution any er diagram screen shots or technical support from forum i will really appreciate.

Thanks in advanc