G/L Account- MIRO

Hi all,

While posting invoice ,

System ask us to provide G/L account

As we know that during the Invoice GR/IR is Debited and Vendors account credited.

I want to know how does the system select which vendor account is to be credited?? e.g If A1000 is my vendor do i have to create the G/L account for that vendor or system select it on its own?

If i have to create it please tell me how to create it?

Thanks in advance.

Monica