I quote too many to my client and most of its i purchase it from amazon now my question how can i know the sales and purchasing cost that related to amazon vender only ?

Let me guide you on what to do so you'll know your sales and purchases cost to amazon vendors only,  marketing6.

You'll want to run the Purchases by Product/Service Detail report to know the purchasing cost to your vendor. To do this, follow the steps below:

1. Go to the Reports menu.
2. Use the Find report by name search bar to search for reports by name. You can also browse the list.
3. Select the report to open it.

At the same time, you can also run the Transactions List by Customer report if you want to know the sales being made. Apart from this, you might consider filtering the reports to specific information to get the information you need. Please go through this article for your guide: Customise Reports in QuickBooks Online.

Fill me in and keep in touch if you have any concerns with your sales and purchases. As always, we're here to get the help you need.