IDOC and Invoice Relationship

Hi Experts,

When i try to find a linkage between inbound Idoc and invoice i don't see the relationship exist in the "Relationship" option on MIR4 or

WE02.

We are using message type INVOIC and idoc type INVOIC01,

I just wanted to know if there is any kind of configuration to set this up ? I trying searching for some options but couldn't find any link.

Thanks

Bhanu