Yes, this is Income. You made a sale: "Does reimbursed expenses consider to be income?"

"We are working on real estate project ,and almost all our expenses are paid back by third-party company."

That's not enough info. Sorry. For example: We Flip Property, so nothing here is income or expense when working on the property. That costs are invested in the project and accrued as Other Current Asset.

"I understand that at the and, my net will be zero. But should I see my reimbursable expenses on expense part  and  reimbursed expenses as income on my P&L or trial balance?"

Now you need to talk to your own CPA.

If this is expense and income, then you see expense and you see income. I pay for $100 of stamps, and charge that to you. I see on my P&L $100 Expense for Postage and $100 revenue, because I charged you for the stamps. That gives Profit, which might be 0.

If this is Property Flipping, the Cost for the subs, materials, permit, etc are Other Current Asset. When the project finally sells, I have Gross Revenue. That means I can "close" Construction in Progress Other Current Asset to COGS (expense). Now I have Profit.

"What I've been doing is :

record/pay bill, click Customer:Job- pick company that I am going to Invoice to."

Assigning that it is a Direct Cost for that name; charging them or not is your separate decision here. Assigning = Tracking. Billable or not is a Status.

Stop using Expense; use Items.

"This kind of transaction creates offset on P&L or trial balance, so in the end I have Zero- no expense and no income. I believe that it is incorrect."

Yes, that is Very Wrong.

Go to QB for Mac:

www.qblittlesquare.com

take some videos, read some articles, get the Manual while you are there.