Cash Paid to Vendors/Suppliers reading, accounts, accounting, difficulty, starting

simeezee

I'm reading the cash flow section of FRA and I'm having difficulty grasping this concept:

Cost of Goods Sold +/- Inventory Delta = Purchases +/- Accounts Payable Delta = $ Paid

I get why we consider the accounts payable - we are trying to figure out how much of the purchases was credit. What I don't get is why the starting point is COGS. COGS is the cost of the inventory sold - that does not mean that inventory was purchased in that accounting period.

Can someone please explain?