Goods receipt without PO

Dear Experts,

I have an issue, where the materials department prepares GR without PO as materials are procured without PO for an amount less than 5000 Rs At the time of receipt a material account is debited and correspondingly GR/IR account is credited (this GL setting has no open item management). Now From the accounts point of view I'm not able set off / debit the GR/IR clearing account.

The GL account property is Post automatically only, so it will not allow a direct posting into this account, we cant even remove it as it comes from OBYC and the posting is done in the background when the Material department does the 501 movement type.