GR/IR Account clearing

Hi ,

We have implemented SAP in 2007 till date we have never cleared the GR/IR clearing account, now we would like to do the same.

What is the Tcode which is used for clearing GR/IR clearing account F.13 or F.19 and while doing this activity what are the parameters or documents or criteria to be checked before clearing the GR/IR clearing account.

Please suggest.

regards

rajesh