Why some supplier bills ( Buying inventory products ) showing as cost of sales in P&L report on quickbooks online?

Glad you've checked the Community Support page, ammar3.

I can share some insights about your inventory items. The Profit and Loss report shows details of your income and expenses. The posting of amounts depends on the accounts or category used on the item lists or transactions. 

That being said, there's a possibility that the item you've used on the bill is categorized in the Cost of Sales account. You can select a different expense account anytime.

Here's how:

1. Click the Gear icon.
2. Go to Products and services.
3. Find the item, then click Edit under the Action column.
4. Change the account under Expense account.
5. Click Save and close.

I'm adding this article in case you need a reference about the process above: Change the account for a product/service item.

To get the best out of your reports, you can customise the Profit and Loss report. Then, memorize and export to Excel for your copy.

Leave a comment below if you have additional questions about your Profit and Loss report. I'm always around to answer.