Tracking purchase expense with items purchase info

Tracking purchase expense with items purchase info

Hi, I can't find this in the thread so I am asking it here.

When I create items in my account and set up recurring invoices that include those items, I think the journal will be something like:

Dr Receivables
Cr Sales

Dr Cost of sales
Cr Inventory

I'm asking because I set up the items to automatically update Cost of sales with the cost price. 

Does this mean I do not have to create a recurring purchase expense for those items? Or do I still create the purchases expense to affect inventory eg.

// Does this happen automatically when setting up purchase info in items?
Dt Purchases
Cr Payables

Dt Inventory
Cr COS

So when the cash comes for the sale:
Dr Bank
Cr Receivables

And when the purchase is paid:

Dt Payables
Cr Bank