Hi Prince,
As rightly said by Manjit, you have to maintain the Revenue Account Determination in VKOA to generate the Accounting of a Billing document in your desired G/L account.
But as you mentioned the COGS, so I am confuse that are you trying to setting up the Revenue account at the time of Billing or you also talking about the PGI when Inventory is getting moved.
Your Material Master Account Assignment Grp is responsible for Revenue A/C determination which you have to take care in VKOA.
And for Inventory you have to set up as per your requirement in OBYC, you can consult with your MM guys.
Thanks,
Suman$