Why the bills I assign to specific customer, I cannot see it in his transactions page ?

I’ll make sure you’ll be able to track his bills in QuickBooks, @adel-tlines-us.

The customer's Transactions page only provides sales entries. If the bill is named after your customer, you’ll want to run the Transaction List by Customer report to track the transactions.

Here’s how:

1. Go to the Reports menu.
2. Enter/select Transaction List by Customer in the Search field.
3. Click Customize.
4. Select the date period and other necessary information.
5. In the Filter section, select his name in the Customer dropdown.
6. Press Run report.

I’ve attached a reference in case you want to keep the same report settings for future use: Memorise reports in QuickBooks Online. It helps you access the information quickly to save time.

If you have other questions or concerns besides tracking bills, you can add them to your reply below. I'm happy to lend a helping hand. Take care!